Anatomy of the central nervous system briefly. Anatomy of the Human Central Nervous System - information. Which doctors should I contact for examination of the Central nervous system?

Gray and white matter of the brain. White matter of the hemispheres. Gray matter of the hemisphere. Frontal lobe. Parietal lobe. Temporal lobe. Occipital lobe. Island.

http://monax.ru/order/ - essays to order (more than 2300 authors in 450 cities of the CIS).

ANATOMY OF THE CENTRAL NERVOUS SYSTEM

ABSTRACT

Topic: "Gray and white matter of the brain"

WHITE MATTER HEMISPHERES

The entire space between the gray matter of the cerebral cortex and the basal ganglia is occupied by white matter. The white matter of the hemispheres is formed by nerve fibers connecting the cortex of one gyrus with the cortex of other gyri of its and the opposite hemispheres, as well as with underlying formations. Topographics in the white matter distinguish four parts, vaguely delimited from each other:

white matter in the gyri between the sulci;

area of ​​white matter in the outer parts of the hemisphere - semi-oval center ( centrum semiovale);

radiant crown ( corona radiata), formed by radiating fibers entering the internal capsule ( capsule interna) and those leaving it;

central substance of the corpus callosum ( corpus callosum), internal capsule and long associative fibers.

Nerve fibers of white matter are divided into associative, commissural and projection.

Association fibers connect different parts of the cortex of the same hemisphere. They are divided into short and long. Short fibers connect neighboring convolutions in the form of arcuate bundles. Long association fibers connect areas of the cortex that are more distant from each other.

Commissural fibers, which are part of the cerebral commissures, or commissures, connect not only symmetrical points, but also the cortex belonging to different lobes of the opposite hemispheres.

Most of the commissural fibers are part of the corpus callosum, which connects the parts of both hemispheres belonging to neencephalon. Two brain adhesions Commissura anterior And commissura fornicis, much smaller in size belong to the olfactory brain rhinencephalon and connect: Commissura anterior- olfactory lobes and both parahippocampal gyri, commissura fornicis- hippocampi.

Projection fibers connect the cerebral cortex with the underlying formations, and through them with the periphery. These fibers are divided into:

centripetal - ascending, corticopetal, afferent. They conduct excitation towards the cortex;

centrifugal (descending, corticofugal, efferent).

Projection fibers in the white matter of the hemisphere closer to the cortex form the corona radiata, and then the main part of them converges into the internal capsule, which is a layer of white matter between the lenticular nucleus ( nucleus lentiformis) on one side, and the caudate nucleus ( nucleus caudatus) and thalamus ( thalamus) - on the other. On a frontal section of the brain, the internal capsule looks like an oblique white stripe that continues into the cerebral peduncle. In the internal capsule the anterior leg is distinguished ( crus anterius), - between the caudate nucleus and the anterior half of the inner surface of the lentiform nucleus, the posterior peduncle ( crus posterius), - between the thalamus and the posterior half of the lentiform nucleus and genu ( genu), lying at the inflection point between both parts of the internal capsule. Projection fibers can be divided according to their length into the following three systems, starting with the longest:

Tractus corticospinalis (pyramidalis) conducts motor volitional impulses to the muscles of the trunk and limbs.

Tractus corticonuclearis- pathways to the motor nuclei of the cranial nerves. All motor fibers are collected in a small space in the internal capsule (the knee and the anterior two-thirds of its posterior limb). And if they are damaged in this place, unilateral paralysis of the opposite side of the body is observed.

Tractus corticopontini- paths from the cerebral cortex to the pontine nuclei. Using these pathways, the cerebral cortex has an inhibitory and regulatory effect on the activity of the cerebellum.

Fibrae thalamocorticalis et corticothalamici- fibers from the thalamus to the cortex and back from the cortex to the thalamus.

GRAY MATTER OF THE HEMISPHERE

Surface of the hemisphere, cloak ( pallium), formed by a uniform layer of gray matter 1.3 - 4.5 mm thick, containing nerve cells. The surface of the cloak has a very complex pattern, consisting of grooves alternating in different directions and ridges between them, called convolutions, gyri. The size and shape of the grooves are subject to significant individual fluctuations, as a result of which not only the brains of different people, but even the hemispheres of the same individual are not quite similar in the pattern of the grooves.

Deep, permanent grooves are used to divide each hemisphere into large areas called lobes. lobi; the latter, in turn, are divided into lobules and convolutions. There are five lobes of the hemisphere: frontal ( lobus frontalis), parietal ( lobus parietalis), temporal ( lobus temporalis), occipital ( lobus occipitalis) and a lobule hidden at the bottom of the lateral sulcus, the so-called islet ( insula).

The superolateral surface of the hemisphere is delimited into lobes by three grooves: the lateral, central and upper end of the parieto-occipital groove. Lateral sulcus ( sulcus cerebri lateralis) begins on the basal surface of the hemisphere from the lateral fossa and then passes to the superolateral surface. Central sulcus ( sulcus centralis) begins at the upper edge of the hemisphere and goes forward and down. The part of the hemisphere located in front of the central sulcus belongs to the frontal lobe. The portion of the brain surface posterior to the central sulcus constitutes the parietal lobe. The posterior border of the parietal lobe is the end of the parieto-occipital sulcus ( sulcus parietooccipitalis), located on the medial surface of the hemisphere.

Each lobe consists of a number of convolutions, called in some places lobules, which are limited by grooves on the surface of the brain.

Frontal lobe

In the posterior part of the outer surface of this lobe there passes sulcus precentralis almost parallel to the direction sulcus centralis. Two furrows run from it in the longitudinal direction: sulcus frontalis superior et sulcus frontalis inferior. Due to this, the frontal lobe is divided into four convolutions. vertical gyrus, gyrus precentralis, located between the central and precentral sulci. The horizontal gyri of the frontal lobe are: superior frontal ( gyrus frontalis superior), middle frontal ( gyrus frontalis medius) and inferior frontal ( gyrus frontalis inferior) shares.

Parietal lobe

On it there is located approximately parallel to the central groove sulcus postcentralis, usually merging with sulcus intraparietalis, which goes in the horizontal direction. Depending on the location of these grooves, the parietal lobe is divided into three gyri. vertical gyrus, gyrus postcentralis, goes behind the central sulcus in the same direction as the precentral gyrus. Above the interparietal sulcus is the superior parietal gyrus, or lobule ( lobulus parietalis superior), below - lobulus parietalis inferior.

Temporal lobe

The lateral surface of this lobe has three longitudinal gyri, delimited from each other sulcus temporalis superio r and sulcus temporalis inferior. stretches between the superior and inferior temporal grooves gyrus temporalis medius. Below it passes gyrus temporalis inferior.

Occipital lobe

The grooves on the lateral surface of this lobe are variable and inconsistent. Of these, the transverse one is distinguished sulcus occipitalis transversus, usually connecting to the end of the interparietal sulcus.

Island

This lobe has the shape of a triangle. The surface of the insula is covered with short convolutions.

The lower surface of the hemisphere in that part that lies anterior to the lateral fossa belongs to the frontal lobe.

Here, parallel to the medial edge of the hemisphere, runs sulcus olfactorius. On the posterior portion of the basal surface of the hemisphere two grooves are visible: sulcus occipitotemporalis, passing in the direction from the occipital pole to the temporal and limiting gyrus occipitotemporalis lateralis, and running parallel to it sulcus collateralis. Between them is located gyrus occipitotemporalis medialis. There are two gyri located medially from the collateral sulcus: between the posterior part of this sulcus and sulcus calcarinus lies gyrus lingualis; between the anterior section of this groove and the deep sulcus hippocampi lies gyrus parahippocampalis. This gyrus, adjacent to the brain stem, is already located on the medial surface of the hemisphere.

On the medial surface of the hemisphere there is a groove of the corpus callosum ( sulcus corpori callosi), running directly above the corpus callosum and continuing with its posterior end into the deep sulcus hippocampi, which is directed forward and downward. Parallel to and above this groove runs along the medial surface of the hemisphere sulcus cinguli. Paracentral lobule ( lobulus paracentralis) is called a small area above the ligular sulcus. Posterior to the paracentral lobule there is a quadrangular surface (the so-called precuneus, precuneus). It belongs to the parietal lobe. Behind the precuneus lies a separate area of ​​the cortex belonging to the occipital lobe - the wedge ( cuneus). Between the lingular sulcus and the sulcus of the corpus callosum stretches the cingulate gyrus ( gyrus cinguli), which, through the isthmus ( isthmus) continues into the parahippocampal gyrus, ending in the uncus ( uncus). Gyrus cinguli, isthmus And gyrus parahippocampali s together form the vaulted gyrus ( gyrus fornicatus), which describes an almost complete circle, open only at the bottom and front. The vaulted gyrus is not related to any of the cloak lobes. It belongs to the limbic region. The limbic region is part of the neocortex of the cerebral hemispheres, occupying the cingulate and parahippocampal gyri; part of the limbic system. Pushing the edge sulcus hippocampi, you can see a narrow jagged gray stripe, representing a rudimentary gyrus gyrus dentatus.

L I T E R A T U R A

Big medical encyclopedia. vol. 6, M., 1977

2. Great medical encyclopedia. vol. 11, M., 1979

3. M.G. Prives, N.K. Lysenkov, V.I. Bushkovich. Human anatomy. M., 1985





To download work you need to join our group for free VKontakte. Just click on the button below. By the way, in our group we help with writing educational papers for free.


A few seconds after checking your subscription, a link to continue downloading your work will appear.
Promote originality of this work. Bypass Antiplagiarism.

REF-Master- a unique program for independent writing of essays, coursework, tests and dissertations. With the help of REF-Master, you can easily and quickly create an original essay, test or coursework based on the finished work - Anatomy of the Central Nervous System.
The main tools used by professional abstract agencies are now at the disposal of abstract.rf users absolutely free of charge!
How to write correctly introduction?

Secrets of the ideal introduction of coursework (as well as essays and diplomas) from professional authors of the largest essay agencies in Russia. Find out how to correctly formulate the relevance of the topic of work, define goals and objectives, indicate the subject, object and methods of research, as well as the theoretical, legal and practical basis of your work.

Secrets of the ideal conclusion of a thesis and term paper from professional authors of the largest essay agencies in Russia. Find out how to correctly formulate conclusions about the work done and make recommendations for improving the issue being studied.


(coursework, diploma or report) without risks, directly from the author.

Similar works:

03/18/2008/creative work

Human anatomy represented in crossword puzzles. To complete this task, not only knowledge of the physiology course will be useful, but also knowledge of the Latin language. Under each word given in Russian, write its translation - you get a Latin proverb.

02/22/2007/abstract

Location and shape of the lungs. The structure of the lungs. Branching of the bronchi. Macro-microscopic structure of the lung. Interlobular connective tissue. Alveolar ducts and sacs. Segmental structure of the lungs. Bronchopulmonary segments.

01/23/2009/abstract

Base of the brain. Hemispheres of the cerebrum. Visual system. Medulla oblongata. The main areas of the right hemisphere of the cerebrum are the frontal, parietal, occipital and temporal lobes. Midbrain, diencephalon and telencephalon. Cerebral cortex.

05/20/2010/abstract

Anatomical structure of the nose, structural features of the mucous membrane. Congenital anomalies of the external nose, causes of acute rhinitis. Types of chronic runny nose, treatment methods. Foreign bodies in the nasal cavity Deformation of the nasal septum, trauma.

05/10/2009/report

Diagnostic difficulties of esophageal diseases. Macroscopic and functional anatomy, characteristics and types of esophageal disorders. Description and classification of esophageal bleeding according to the amount of blood or fluid required to replenish the volume.

03/15/2009/abstract

Chronic obliterating diseases of the arteries of the lower extremities as congenital or acquired disorders of arterial patency in the form of stenosis or occlusion. Chronic ischemia of tissues of the lower extremities of varying severity and changes in cells.

Ministry of Education of the Republic of Belarus

Educational institution

"Belarusian State University of Informatics

and radio electronics"

Department of Engineering Psychology and Ergonomics

ANATOMY AND PHYSIOLOGY

CENTRAL NERVOUS SYSTEM

Methodical manual

for students of specialty 1 –

"Engineering and psychological support of information technologies"

correspondence courses

Minsk BSUIR 2011

Introduction…………………………………………………………………………………………

Topic 1. The cell is the main structural unit of the nervous system……..….

Topic 2. Synaptic impulse transmission.…………………………………..

Topic 3. Structure and functions of the brain……..…………………….…..

Topic 4. Structure and functions of the spinal cord……………………………………………………

Topic 5. Telencephalon, structure and functions………………………………...

Topic 6. Motor centers……………………………………………………………………..

Topic 7. Autonomic nervous system………………………………………………………

Topic 8. Neuroendocrine system…………..……………………………..

Literature……………………………………………………………………….

INTRODUCTION

Studying the discipline “Anatomy and physiology of the central nervous system” − an important component of the basic training of systems engineers. The purpose of teaching this discipline is to acquire knowledge on the formation of the information system of the brain, the transmission of information to the central parts of the nervous system via afferent pathways, as well as its transmission and access to the “periphery” via efferent pathways. Therefore, this methodological manual provides an idea of ​​the activity of the central nervous system (CNS) as the morphofunctional basis of neuropsychological processes; the structure and functions of the central nervous system, which is responsible for collecting, processing information, transmitting it to the higher parts of the cerebral cortex for making management decisions; − The main mechanisms that ensure human life (metabolism, thermoregulation, neurohumoral regulation, systemogenesis), which are responsible for the reliable functioning of its systems, are considered. After each topic under consideration, control questions are given to consolidate and self-check students’ knowledge. At the end of the manual there is a list of tasks for the test. The literature provides a list of sources with rich illustrative material.

The knowledge gained will subsequently serve as the basis for the study of subsequent disciplines in the natural sciences (psychophysiology, psychology, etc.).

Topic 1. THE CELL IS THE BASIC STRUCTURAL UNIT OF THE NERVOUS SYSTEM

The entire nervous system is divided into central and peripheral. The central nervous system (CNS) includes the brain and spinal cord. From them nerve fibers spread throughout the body − peripheral nervous system. It connects the brain to the senses and executive organs − muscles and glands.

Anatomy of the central nervous system studies the structure of its component parts. Physiology studies the mechanisms of their joint work.

All living organisms have the ability to respond to physical and chemical changes in the environment. Stimuli from the external environment (light, sound, smell, touch, etc.) are converted by special sensitive cells (receptors) into nerve impulses − a series of electrical and chemical changes in a nerve fiber. Nerve impulses are transmitted through sensitive (afferent) nerve fibers in the spinal cord and brain. Here the corresponding command impulses are generated, which are transmitted via motor (efferent) nerve fibers to the executive organs (muscles, glands). These executive organs are called effectors.

Basic function of the nervous system − integration of external influences with the corresponding adaptive reaction of the body.

The central nervous system consists of two types of nerve cells: neurons and glial cells, or neuroglia. The human brain is the most complex of all systems in the Universe known to science. Weighing approximately 1,250 g, the brain contains 100 billion nerve neurons connected in an incredibly complex network. Neurons are surrounded by an even larger number of glial cells, which form a supporting and nutritional basis for neurons - glia (Greek "glia" − glue), which performs many other functions that have not yet been fully studied. The space between nerve cells (intercellular space) is filled with water with salts, carbohydrates, proteins, and fats dissolved in it. Smallest blood vessels − capillaries − located in a network between nerve cells.

Guidelines

The functions of neurons include processing information, which means perceiving it, transmitting it to other cells, and encoding this information. The neuron performs all these operations thanks to its special structure.

Despite some diversity in the shape of neurons, most of them have more a large part called body (soma), and several shoots. Usually there is one longer process called axon, and several thinner and shorter, but branching processes called dendrites. The neuron body size is 5-100 micrometers. The length of the axon can be many times greater than the size of the body and reach 1 meter.

The functions of a neuron for processing information are distributed between its parts as follows. Dendrites and the cell body perceive input signals. The cell body sums them up, averages them, combines them and “makes a decision”: to transmit these signals further or not, that is, it forms a response. The axon will transmit output signals to its endings (terminals). Axon terminals transmit information to other neurons, usually through specialized contact sites called synapses. The signals transmitted by neurons are electrical in nature.

Depending on the balance of impulses received by the dendrites of an individual neuron, the cell is activated (or not), and it transmits the impulse along its axon to the dendrites of another nerve cell with which its axon is connected. In this way, each of the 100 billion cells can connect to 100,000 other nerve cells.

The bodies of nerve cells tightly adjacent to each other are perceived by the naked eye as “gray matter”. Cells form folded sheets, such as the cerebral cortex, and organize them into clusters called nuclei and network-like structures. Under a microscope, the structural patterns of different areas of the cerebral cortex can be clearly distinguished. axons, or "white matter", form the main trunks, or "fiber tracts", connecting the cell bodies. The sizes of nerve cells range from 20 to 100 microns (1 micron is equal to a millionth of a meter).

Glial cells include stellate cells (astrocytes), very large cells (oligodendrocytes) and very small cells (microglia). Stellate cells serve as a support for neurons, an intermediary between the neuron and the capillary for the transfer of nutrients, and a reserve material for “repairing” damaged neurons. Oligodendrocytes form myelin − a substance that coats axons and promotes faster signal transmission. Microglia are needed when and where there is damage to the nervous system. Microglial cells migrate to damaged areas and, turning into macrophages, like protective blood cells, destroy waste products. Myelin is formed from a glial cell coiled around the axon.

Security questions:

1. What does the anatomy of the central nervous system study?

2. What does the physiology of the central nervous system study?

3. What is classified as the central nervous system and the peripheral?

4. What is the main function of the nervous system?

5. Name the types of nerve cells and indicate their ratio in the central nervous system.

6. What are the structure and functions of a neuron?

7. Name the types and functions of glial cells.

8. What are “gray matter” and “white matter”?

Topic 2. SYNAPTIC IMPULSE TRANSMISSION

Synapses on a typical neuron in the brain are either exciting, or brake, depending on the type of mediator released in them. Synapses can also be classified by their location on the surface of the receiving neuron - on the cell body, on the shaft or "spine" of the dendrite, or on the axon. Depending on the method of transmission, chemical, electrical and mixed synapses are distinguished.

Guidelines

The process of chemical transmission goes through a number of stages: synthesis of the mediator, its accumulation, release, interaction with the receptor and cessation of the action of the mediator. Each of these stages has been characterized in detail, and drugs have been found that selectively enhance or block a specific stage.

Neurotransmitter(neurotransmitter, neurotransmitter) is a substance that is synthesized in a neuron, contained in presynaptic terminals, released into the synaptic cleft in response to a nerve impulse and acts on special areas of the postsynaptic cell, causing changes in the membrane potential and cell metabolism. For a long time it was believed that the function of a neurotransmitter was only to open (or even close) ion channels in the postsynaptic membrane. It was also known that the same substance can always be released from the terminal of one axon. Later, new substances were discovered that appear in the synapse area at the time of excitation transmission. They were called neuromodulators. Studying the chemical structure of all discovered mediators and neuromodulators clarified the situation. All studied substances related to synaptic transmission of excitation were divided into three groups: amino acids, monoamines and peptides. All these substances are now called mediators.

There are “neuromodulators” that do not have an independent physiological effect, but modify the effect of neurotransmitters. The action of neuromodulators is tonic in nature - slow development and long duration of action. Its origin is not necessarily neural; for example, glia can synthesize a number of neuromodulators. The action is not initiated by a nerve impulse and is not always associated with the effect of a mediator. The targets of influence are not only the receptors on the postsynaptic membrane, but different parts of the neuron, including intracellular ones.

In recent years, with the discovery of a new class of chemical compounds in the brain, neuropeptides, the number of known chemical messenger systems in the brain has increased dramatically. Neuropeptides represent chains of amino acid residues. Many of them are localized in axon terminals. Neuropeptides differ from previously identified mediators in that they organize such complex phenomena as memory, thirst, sexual desire, etc.

Security questions:

1. What is a synapse?

2. Name the types of synapses.

3. What is characteristic of electrical synaptic transmission?

4. What is characteristic of chemical signal transmission?

5. Define a neurotransmitter. What groups are synaptic transmitters divided into based on their chemical structure?

6. What are neuromodulators? What is their origin and action?

7. What are neuropeptides?

Topic 3. STRUCTURE AND FUNCTIONS OF THE BRAIN

In Latin brain denoted by the word "cerebrit", and in ancient Greek - "cephalon". The brain is located in the cranial cavity and has a shape that generally corresponds to the internal contours of the cranial cavity.

The brain has three large parts: cerebral hemispheres, or hemispheres, cerebellum And brain stem.

The largest part of the entire brain is occupied by the cerebral hemispheres, followed by the cerebellum in size, and the rest is the brain stem. Both hemispheres, left and right, are separated from each other by a fissure. In its depths, the hemispheres are connected to each other by a large commissure - the corpus callosum. There are also two less massive commissures, including the so-called anterior commissure.

From the lower surface of the brain, not only the lower side of the cerebral hemispheres and cerebellum is visible, but also the entire lower surface of the brain stem, as well as the cranial nerves extending from the brain. From the side, mainly the cerebral cortex is visible.

Guidelines

Vital processes stop if any vital center of the brain is destroyed: cardiovascular or respiratory. If we compare hierarchically these centers with their corresponding higher and lower ones (in the spinal cord), then they can be called the main organizers of blood circulation and respiration. The spinal cord, i.e. its motor neurons going directly to the muscles, is the performer. And in the role of initiator and modulator are the hypothalamus (diencephalon) and the cerebral cortex (endbrain).

Located in the medulla oblongata cardiovascular center. The cardiovascular system includes the vagus nerve nuclei, which have parasympathetic effects on the heart, and the so-called vasomotor center, which has sympathetic effects on the heart and blood vessels. In the vasomotor center, two zones are distinguished: pressor (constricts blood vessels) and depressor (dilates blood vessels), which are in a reciprocal relationship. The pressor zone is “switched on” by chemoreceptors (react to the composition of the blood) and exteroceptors, and the depressor zone is activated by baroreceptors (react to the pressure experienced by the walls of blood vessels). The hierarchically highest center of parasympathetic and sympathetic innervation is the hypothalamus. It determines what effects will occur in the cardiovascular system. The hypothalamus determines this in accordance with the current need of the whole organism at a given moment.

Respiratory center partly located in the hindbrain pons and partly in the medulla oblongata. We can say that there is a separate inhalation center (in the pons) and an exhalation center (in the medulla oblongata). These centers are in a reciprocal relationship. Inhalation occurs when the external intercostal muscles contract, and exhalation occurs when the internal intercostal muscles contract. Commands to the muscles come from motor neurons in the spinal cord. The spinal cord receives commands from the inhalation and exhalation centers. The inhalation center is characterized by constant impulse activity. But it is interrupted by information coming from stretch receptors, which are located in the walls of the lungs. The expansion of the lungs from inhalation initiates exhalation. The respiratory rate can be modulated by the vagus nerve and higher centers: the hypothalamus and cerebral cortex. For example, when speaking, we can consciously regulate the duration of inhalation and exhalation, since we are forced to pronounce sounds of different durations.

In addition, the medulla oblongata contains the nuclei of several cranial nerves. In total, humans have 12 pairs of cranial nerves, of which four pairs are located in the medulla oblongata. These are the hypoglossal nerve (XII), accessory (XI), vagus (X) and glossopharyngeal (IX) nerve. Thanks to the nuclei of the glossopharyngeal nerve, movements of the muscles of the pharynx occur, which means that several reflexes that are important for the body are realized: coughing, sneezing, swallowing, vomiting, and phonation also occurs - the pronunciation of speech sounds. In this regard, it is believed that the corresponding centers are located in the medulla oblongata: sneezing, coughing, vomiting.

In addition, the medulla oblongata contains the vestibular nuclei, which regulate the function of balance.

TO hindbrain include the pons and cerebellum. The cavity of the hindbrain is the fourth cerebral ventricle (like a continuing and expanding spinal canal). The pons Varoliev is formed by powerful conductive pathways. The cerebellum is a motor center with numerous connections to other parts of the brain. The binding fibers are collected in bundles and form three pairs of legs. The lower legs provide communication with the medulla oblongata, the middle ones provide communication with the pons, and through it with the cortex, and the upper ones with the midbrain.

The cerebellum makes up only 10% of the brain's mass, but contains more than half of all neurons in the central nervous system. The motor functions of the cerebellum include the regulation of muscle tone, body posture and balance. The ancient cerebellum is responsible for this . The cerebellum coordinates posture and purposeful movements. The old and new cerebellum are responsible for this . The cerebellum is also involved in programming various goal-directed movements, which include ballistic movements, sports movements, such as throwing a ball, playing musical instruments, touch typing, etc. The assumption of the participation of the cerebellum in thinking processes is studied: the presence of common neural systems for control of movement and thinking.

At the bottom of the cerebral ventricle, which has a rhomboid shape (also called the rhomboid fossa), are located the nuclei of the vestibulocochlear (VIII), facial (VII), abducens (VI) and partially trigeminal (V) cranial nerves.

Midbrain is a very constant, evolutionarily low-variable part of the brain. Its nuclear structures are associated with the regulation of postural movements (red nucleus), with participation in the activity of the extrapyramidal motor system (substantia nigra and red nucleus), with indicative reactions to visual and sound signals (quadrigeminal). The superior colliculus is the primary visual center, and the inferior colliculus is the primary auditory center.

The so-called aqueduct of Sylvius passes through the midbrain, connecting the 4th and 3rd cerebral ventricles. Here are also the nuclei of the 3rd (oculomotor), 4th (trochlear) and one of the nuclei of the 5th (trigeminal) cranial nerves. The 3rd and 4th cranial nerves regulate eye movements. Considering that the superior colliculus, which receives information from vision receptors, is also located here, the midbrain can be considered the place where visual-oculomotor functions are concentrated.

Diencephalon represented by one formation - the thalamus. The thalamus has a round, ovoid shape. The historical name of the thalamus is the visual thalamus, or sensory thalamus. It received this name because of its main function, which was established a long time ago. The thalamus is the collector of all sensory information. This means that it receives information from all types of receptors, from all senses (vision, hearing, taste, smell, touch), proprioceptors, interoreceptors, vestibuloreceptors.

Instead of the name "diencephalon" the name "thalamus" is often used. The thalamus occupies the central part of the diencephalon. It forms the floor and walls of the 3rd cerebral ventricle. Anatomically, the thalamus has appendages: superior appendage (epithalamus) , inferior appendage (hypothalamus) , posterior part (metathalamus) , and optic chiasm. or visual chiasma.

Epithalamus consists of several formations. The biggest one is pineal gland, or pineal gland (pineal gland). This is an endocrine gland that secretes melatonin. Norepinephrine, histamine and serotonin are also found in the pineal gland. The participation of these substances in the regulation of circadian rhythms (daily rhythms of activity associated with illumination) has been proven.

Metathalamus consists of the lateral geniculate bodies (secondary visual centers) and the medial geniculate bodies (secondary auditory center).

Hypothalamus is at the same time the highest center of the autonomic nervous system, a “chemical analyzer” of the composition of blood and cerebrospinal fluid, and an endocrine gland. It is part of the limbic system of the brain. Part of the hypothalamus is pituitary- formation the size of a pea. The pituitary gland is an important endocrine gland: its hormones regulate the activity of all other glands.

Due to the fact that the hypothalamus has its own various osmo- and chemoreceptors, it can determine the sufficiency of the concentration of various substances in the body fluids passing through the hypothalamic tissue - blood and cerebrospinal fluid. In accordance with the result of the analysis, it can enhance or weaken various metabolic processes both by sending nerve impulses to all autonomic centers and by releasing biologically active substances - liberins and statins. Thus, the hypothalamus is the highest regulator of eating, sexual, aggressive and defensive behavior, that is, the main biological motivations.

Since the hypothalamus is an integral part of the limbic system, it is also the center for the integration of somatic (related to motor reactions in accordance with sensory organ data) and autonomic functions, namely: it provides somatic functions in accordance with the needs of the whole organism. For example, if for the body at the moment a biologically important task is defensive behavior, which, first of all, depends on the effective functioning of skeletal muscles and sensory organs (see, hear, move). But the effective work of muscles, in turn, depends not only on the speed of nerve impulses, but also on the provision of muscles and nerves with energy resources and oxygen, etc. Therefore, we can say that the hypothalamus provides “internal” support for “external” behavior.

The nuclei of the thalamus are divided functionally into three groups: relay (switching), associative (integrative) and nonspecific (modulating).

Switch cores- This is an intermediate link in long conducting pathways (afferent pathways) coming from all receptors of the trunk, limbs and head. These afferent signals are then transmitted to the corresponding analyzer zones of the cerebral cortex. It is this part of the thalamus that is the “sensitive tubercle”. This functionally includes both the lateral and medial geniculate bodies, since from them information is switched to the occipital and temporal cortex, respectively.

The associative nuclei of the thalamus connect with each other different nuclei within the thalamus itself, as well as the thalamus itself with the associative zones of the cerebral cortex. Thanks to these connections, for example, it is possible to form a “body diagram” and undergo various types of gnostic (cognitive) processes when a word and a visual image are connected together.

The nonspecific nuclei of the thalamus form the most evolutionarily ancient part of the thalamus. This nuclei of the reticular formation. They receive sensory information from all ascending pathways and from the motor centers of the midbrain. The cells of the reticular formation are not able to distinguish which modality the signal is received. But this is exactly how it comes into a state of excitement, as if “infected” with energy and, in turn, has a modulating effect on the cerebral cortex, namely, activating attention. That's why they call her reticular activating system of the brain.

The optic nerve, or 2nd cranial nerve, passes through the diencephalon, starting from the receptors of the retina. Here, in the “territory” of the diencephalon, the optic nerve makes a partial decussation and then continues as a visual tract leading to the primary and secondary visual centers, and further to the visual cortex of the brain.

Security questions:

1. Name the main parts of the brain.

2. Where is the medulla oblongata located and what is it?

3. Name the functions of the medulla oblongata.

4. What is the hindbrain and what are its functions?

5. What is the midbrain and what are its functions?

6. What is the diencephalon?

7. What is the structure and purpose of the epithalamus?

8. What is the structure and purpose of the metathalamus?

9. What is the structure and purpose of the hypothalamus?

10.Give a description of each of the three groups of thalamic nuclei.

Topic 4. STRUCTURE AND FUNCTIONS OF THE SPINAL CORD

The spinal cord is located in the spinal canal. It is approximately cylindrical in shape. Its upper end passes into the medulla oblongata, and the lower end into the filum terminale (cauda equina).

In an adult, the spinal cord begins at the upper edge of the first cervical vertebra and ends at the level of the second lumbar vertebra. The spinal cord has a segmental structure. It has 31 segments: 8 cervical, 12 thoracic, 5 lumbar, 5 sacral and 1 coccygeal. (Sometimes they say that there are 31-33 segments in total, and in the coccygeal region there are 1-3. The fact is that the coccygeal vertebrae are fused into one).

Each segment is designated by the vertebra near which its roots emerge. But this does not mean that each segment is located exactly opposite the corresponding vertebra. In the embryonic state, the length of the spinal cord is approximately equal to the length of the spine. But in the process of individual development, the spine grows faster than the brain. As a result, the spinal cord is shorter than the spine. Therefore, in the upper parts of the spinal cord, the segments correspond to the vertebrae, and their roots exit there, horizontally. In the lower sections, the spinal canal no longer contains brain matter, and the segments corresponding to the vertebrae are located higher. Therefore, at the bottom, the roots in the form of a bundle (cauda equina) descend down to the intervertebral foramina and then exit the spine.

Guidelines

The spinal cord is covered by three membranes. The outer meninges are called hard. The middle shell is called arachnoid. The space between these shells is called subdural. The inner shell is called vascular. The space between the arachnoid and choroid is called subarachnoid or subarachnoid. The choroid and arachnoid membrane form the pia mater of the brain. The spaces between the membranes are filled with cerebrospinal fluid (CSF). Synonyms for CSF are the names “cerebrospinal fluid” and “cerebrospinal fluid” .

The spinal cord and brain have the same membranes and communicating spaces between the membranes. In addition, the central canal of the spinal cord continues into the brain. Expanding, it forms the ventricles of the brain - cavities also filled with cerebrospinal fluid.

The meninges and cerebrospinal fluid protect the spinal cord from mechanical damage. Cerebrospinal fluid also serves to chemically protect brain tissue from the effects of adverse substances. CSF is formed by filtration from arterial blood in the choroid plexus of the 4th and lateral ventricles of the brain, and its outflow occurs into the venous blood in the region of the 4th ventricle. Various substances that easily pass from the digestive tract into the blood cannot penetrate into the cerebrospinal fluid as easily, due to blood-brain barrier, which works as a filter, selecting substances that are beneficial and “discarding” substances harmful to the central nervous system.

Security questions:

1. Describe the longitudinal structure of the spinal cord and its location.

2. What membranes surround the spinal cord, what are their functions?

3. What is cerebrospinal fluid, where is it located and what are its functions?

4. What is the function of the blood-brain barrier?

Topic 5. THE END BRAIN, STRUCTURE AND FUNCTION

The telencephalon anatomically consists of two hemispheres connected to each other by the corpus callosum , arch and anterior commissure. Each hemisphere functionally and anatomically consists of the cortex and subcortical (basal) nuclei. In the thickness of the cerebral hemispheres there are cavities of the 1st and 2nd cerebral ventricles, which have a complex configuration. These ventricles are also called the anterior (1st) and posterior (2nd) ventricles of the telencephalon.

The subcortical nuclei of the telencephalon include, firstly, three paired formations included in the striopallidal system, which is important in the regulation of movements: the caudate nucleus, the globus pallidus , fence . The striopallidal system is part of the extrapyramidal motor system.

Secondly, the “subcortex” includes the amygdala nucleus and the nuclei of the septum pellucidum and other formations. The functions of these nuclei are associated with the regulation of complex forms of behavior and mental functions, such as instincts, emotions, motivation, memory.

Most often, the above subcortical nuclei, or basal nuclei, that is, located at the base of the cortex, like the foundation of a house, are simply called “subcortex.” But sometimes the subcortex is called everything that is below the cortex, but above the brain stem, and then the thalamus with its appendages is also included in it.

In general, subcortical structures perform integrative functions.

In the brain, as in the spinal cord, there are three types of substance: gray, white And mesh. Accordingly, the first is formed by the bodies of neurons, the second by myelinated processes of neurons collected in ordered bundles, and the third by interspersed bodies and processes running in different directions.

The reticular substance, or reticular formation, is located more centrally. The cell bodies of neurons (gray matter) are arranged in clusters called nuclei. Sometimes instead of the word “nuclei” the word node or ganglion is used. Bundles of myelinated fibers, just like in the spinal cord, form pathways: short and long. There are two types of shortcuts: commissural and associative.

Guidelines

Cranial nerves are analogues of spinal nerves. In humans, there are 12 pairs of cranial nerves. They are usually designated by Roman numerals, and each has its own name and function.

The function of the spinal nerves is to transmit information from receptors located in various parts of the body to the central nervous system (via the dorsal roots of the spinal cord) and transmit information from the central nervous system to the muscles that carry out body movements, muscles of internal organs and glands (via the anterior roots spinal cord). Similar to the spinal nerves, the cranial nerves transmit information from receptors located in the head (sensory organs) to the brain stem and transmit information from the brain centers to the muscles and glands located in the head.

There is another analogy. The spinal nerves that control the skeletal muscles of the body are influenced by the higher motor centers of the brain. In the same way, the cranial nerves that control the skeletal muscles of the head are subject to the influence of the cortical motor zones, thanks to which voluntary movements of the tongue, nose, ear, eyes, eyelids, etc. are possible.

Thus, cranial nerves are peripheral nerves not related to the central nervous system. It seems incredible, but this is exactly how it is. It’s just that in the head area, everything – both the center (brain) and the periphery (receptors and cranial nerves) are geographically close to each other. It is because of this that the clear segmentation that is observed in the spinal nerves is disrupted, when the sensory roots of the nerves are strictly on the posterior surface, and the motor roots are on the anterior surface of the spinal cord. Moreover, some cranial nerves generally have either only a sensory branch (optic nerve) or only a motor branch (oculomotor nerve).

To those organs (muscles, glands) that are located outside the skull, as well as from receptors located outside the skull, cranial nerves pass through certain openings of the skull: jugular, occipital, temporal, openings of the ethmoid bone.

Reticular formation(RF) – the reticular substance is a collection of nerve cells that forms a network of densely intertwined processes running in different directions. The reticular formation is located in the central part of the brain stem and in separate inclusions in the diencephalon. RF cells are not directly connected to the ascending pathways from the receptors to the cortex. But all sensory pathways ascending to the cortex send their branches to the RF. This means that the RF receives the same number of impulses as higher-level centers, although it does not distinguish between them “by origin”. But thanks to them, a constantly high level of excitation in the RF cells is maintained. In addition, the excitation of the RF depends on the concentration of chemicals (humoral factors) in the CSF. Thus, the RF serves as an energy accumulator, which it directs mainly to increasing activity, i.e., the level of wakefulness, of the cortex. However, RF also has an activating effect in the descending direction: controlling spinal cord reflexes through the reticulospinal tracts, changing the activity of alpha and gamma motor neurons of the spinal cord.

Security questions:

1. Describe the structure and location of the telencephalon.

2. Name three types of substance that make up the brain.

3. Describe the structure and location of the reticular formation.

4. What are the functions of the reticular formation?

Topic 6. MOTOR CENTERS

All motor functions (or simply movements) can be divided into two types: purposeful and posnotonic.

Purposeful movements– these are movements aimed at some goal associated with movement in space; these are labor movements associated with the need to take, lift, hold, let go of something, etc. These are also various manipulative movements that a person learns throughout his life. These are mainly voluntary movements. Although the protective flexion reflex can also be called goal-directed, since it aims to interrupt contact with a painful stimulus.

Postnotonic movements, or postural, provide a position in space that is usual for a given organism, that is, in the gravitational field of the Earth. For humans, this is a vertical position. Postural movements are based on innate reflex reactions. The name "postural" comes from the English word "posture" which means “pose, figure.”

The structures of the central nervous system responsible for the nervous regulation of motor functions are called motor centers. They are localized in various parts of the central nervous system.

Motor centers that regulate postural movements are concentrated in the structures of the brain stem. Motor centers that control purposeful movements are located at higher levels of the brain - in the cerebral hemispheres: subcortical and cortical centers.

Guidelines

The brainstem includes the medulla oblongata, part of the hindbrain, and the midbrain. At the level of the medulla oblongata, the following motor centers are located: vestibular nuclei and reticular formation. Vestibular nuclei receive information from balance receptors located in the vestibule of the inner ear , and in accordance with it, excitatory signals are sent to the spinal cord along the vestibulospinal tract. The impulses are intended for the extensor muscles of the torso and limbs, thanks to the work of which a person who has slipped or tripped is able to immediately react: straighten up, find support again, i.e., restore balance. From reticular formation The medulla oblongata also begins the lateral reticulospinal tract, which innervates the maximally located flexor muscles of the trunk and limbs.

Main motor function of the medulla oblongata–maintaining balance automatically, without the participation of consciousness.

The pons of the hindbrain contains the nuclei of the reticulospinal tract, which excites the motor neurons of the extensors. This means that these and the vestibulospinal centers act “at the same time.”

In the midbrain, several nerve centers are related to the regulation of movements: the red nucleus, the roof of the brain, or the quadrigeminal, the substantia nigra , as well as the reticular formation.

From red kernel the rubrospinal tract begins. Thanks to impulses transmitted along this path, body posture is regulated, for which the red nucleus is credited with the role of the main anti-gravity mechanism. The red nucleus increases the tone of the flexors of the upper extremities and ensures coordination of various muscle groups (this is called synergy) when walking, jumping, and climbing. However, the red nucleus itself is constantly under the control of centers higher in relation to it - the subcortical, or basal nuclei.

Four Hills consists of the superior and inferior colliculi, which are simultaneously not only motor centers, but also the primary centers of vision (superior colliculus) and hearing (inferior colliculus). From them begin the tectospinal tracts, along which, in accordance with visual and auditory information, a command is transmitted to turn the neck or eyes and ears in the direction of a perceived stimulus that is new for a given situation. This reaction is called the orienting reflex, or the “what is it?” reflex.

Black substance has synaptic connections with the basal subcortical nuclei. The transmitter at these synapses is dopamine. With its help, the substantia nigra has a stimulating effect on the basal ganglia.

Reticulospinal tract, starting from the reticular formation of the midbrain, has an exciting effect on gamma motor neurons of all muscles of the trunk and proximal limbs.

Cerebellum, like the motor centers of the brain stem, ensures the tone of skeletal muscles, regulation of postnotonic functions, coordination of posture-tonic movements with purposeful ones. The cerebellum has bilateral connections with the cerebral cortex, and therefore it is a corrector of all types of movements. It calculates the amplitude and trajectory of movements.

TO basal ganglia, or nuclei, include several subcortical structures: the caudate nucleus, the fence and the globus pallidus. Another name for this complex is the striopallidal system. This system is part of an even more complex motor system - the extrapyramidal. The basal ganglia mainly perform the functions of controlling rhythmic movements and ancient automatisms (walking, running, swimming, jumping). They also provide a background that facilitates specialized movements and also provides accompanying movements.

Higher motor centers are located in the neocortex of the cerebral hemispheres. The motor centers of the cortex have a specific localization: these are precetral gyrus, located anterior to the central Rolland's fissure. Their localization was established experimentally by electrical stimulation of various points in the motor zone. When certain points were stimulated, movements of the contralateral limb were obtained. According to modern concepts, it is not individual muscles that are represented in the cortex, but entire movements performed by muscles. grouping around a specific joint. The motor cortex itself contains "higher order" motor neurons, or command neurons, which bring into action various muscles. This motor area is called the primary motor area. Adjacent to it is the secondary motor area, which is called premotor. Its functions are related to the regulation of motor functions that are of a social nature, for example, writing and speech. It is from here, from these motor areas, that both pyramidal descending tracts originate.

The higher motor centers are located next to the higher sensory centers, which are located in postcentral gyrus. Sensory areas(zones) receive information from skin receptors and proprioceptors located on all parts of the body. Here, similarly to the motor zones, all areas of the body and face are represented. Therefore, the postcentral region of the cortex is called somatosensory. However, the size of the representations does not depend on the size of the body part itself, but on the importance of the information coming from it. Therefore, the representation of the torso and lower limb is relatively small, but the representation of the hand is huge.

It has been shown that the motor and sensory areas partially overlap, so both zones are called the same word - the sensorimotor zone.

Security questions:

1. How are movements classified?

2. Name the brainstem and subcortical motor centers.

3. What are the functions of the red nucleus?

4. What are the functions of the quadrigeminal region?

5. What are the functions of the substantia nigra?

6. What are the functions of the basal ganglia?

7. Indicate the location and name the functions of sensorimotor centers.

Topic 7. AUTONOMIC NERVOUS SYSTEM

The nervous system is usually divided into somatic and autonomic. To tasks somatic system includes responding to external signals and, in accordance with data from the senses, carrying out motor reactions. For example, the task of avoiding the source of unpleasant, harmful influences and approaching the sources of pleasant, beneficial influences.

The name somatic nervous system comes from the word “soma,” which means “body” in Latin. Not only the cell, but also our microorganism has a body - this is our entire muscular membrane, consisting of skeletal (striated muscles), thanks to which the body is able to produce movements.

Guidelines

Autonomic nervous system(autonomic nervous system, visceral nervous system) - a section of the nervous system that regulates the activity of internal organs, endocrine and exocrine glands, blood and lymphatic vessels. The autonomic nervous system regulates the state of the internal environment of the body, controls metabolism and the associated functions of respiration, blood circulation, digestion, excretion and reproduction. The activity of the autonomic nervous system is mainly involuntary and is not directly controlled by consciousness. The main effector organs of the autonomic system are the smooth muscles of internal organs, blood vessels and glands.

Vegetative And somatic parts of the nervous system act cooperatively. Their neural structures cannot be completely separated from each other. Therefore, this division is analytical, since both skeletal muscles and internal organs are simultaneously involved in the body’s reactions to various stimuli (if only because they ensure the functioning of the muscles).

The vegetative and somatic systems have the following differences: in the location of their centers; in the structure of their peripheral parts; in the characteristics of nerve fibers; depending on consciousness.

There are two functional divisions of the autonomic nervous system: segmental-peripheral, providing autonomic innervation of individual body segments and related internal organs, and central (suprasegmental), which carries out integration, unification of all segmental apparatuses, subordination of their activities to the general functional tasks of the whole organism.

At the segmental-peripheral level of the autonomic nervous system, there are two relatively independent parts of it - sympathetic and parasympathetic, the coordinated activity of which ensures fine regulation of the functions of internal organs and metabolism. Sometimes the influence of these parts or systems on an organ is opposite in effect, and an increase in the activity of one system is accompanied by inhibition of the activity of another. In the regulation of some other functions, both systems act unidirectionally.

Sympathetic segmental spinal centers are located in the lateral horns of the thoracic and lumbar spinal cord. From the cells of these centers, autonomic fibers originate, heading to the sympathetic nodes or autonomic ganglia (preganglionic fibers). The ganglia are located in chains on both sides of the spine, making up the so-called sympathetic trunks, in which there are 2-3 cervical, 10-12 thoracic nodes, 4-5 lumbar, 4-5 sacral nodes. The right and left trunks at the level of the first coccygeal vertebra are connected and form a loop, in the middle of which there is one unpaired coccygeal node. Postganglionic fibers depart from the nodes and go to the innervated organs. Some of the preganglionic fibers, without interruption in the ganglia of the sympathetic trunks, reach the celiac and inferior mesenteric autonomic plexuses, from the nerve cells of which postganglionic fibers extend to the innervated organ.

Parasympathetic the nerve centers are located in the autonomic nuclei of the brain stem, as well as in the sacral part of the spinal cord, where parasympathetic preganglionic fibers begin; these fibers end in the vegetative nodes located in the wall of the working organ or in the immediate vicinity of it, and therefore the postganglionic fibers of this system are extremely short. Parasympathetic fibers pass from the autonomic centers located in the brain stem as part of the oculomotor, facial, glossopharyngeal and vagus nerves. They innervate the smooth muscles of the eye (except for the dilator pupillary muscle, which receives innervation from the sympathetic part of the autonomic nervous system), the lacrimal and salivary glands, as well as the vessels and internal organs of the thoracic and abdominal cavities. The sacral parasympathetic center provides segmental autonomic innervation of the bladder, sigmoid colon and rectum, and genitals.

Increased activity of the sympathetic nervous system is accompanied by dilation of the pupil, increased heart rate and increased blood pressure, dilation of small bronchi, decreased intestinal motility and contraction of the sphincters of the bladder and rectum. Increased activity of the parasympathetic system is characterized by constriction of the pupil, slowing of heart contractions, decreased blood pressure, spasm of the small bronchi, increased intestinal motility and relaxation of the sphincters of the bladder and rectum. The consistency of the physiological influences of these systems ensures homeostasis– harmonious physiological state of organs and the body as a whole at an optimal level.

The activity of sympathetic and parasympathetic segmental-peripheral formations is under control central suprasegmental autonomic apparatus, which include the respiratory and vasomotor stem centers, the hypothalamic region and the limbic system of the brain. In case of defeat respiratory And vasomotor stem centers respiratory and cardiac problems occur. Cores hypothalamic region regulate cardiovascular activity, body temperature, gastrointestinal tract function, urination, sexual function, all types of metabolism, endocrine system, sleep, etc. The nuclei of the anterior hypothalamic region are associated primarily with the function of the parasympathetic system, and the posterior region with the function of the sympathetic system . Limbic system not only takes part in the regulation of the activity of autonomic functions, but largely determines the autonomic “profile” of the individual, his general emotional and behavioral background, performance and memory, ensuring a close functional relationship between the somatic and autonomic systems.

Limbic the system is a functional association of brain structures involved in the organization of emotional and motivational behavior, such as food, sexual, and defensive instincts. This system is involved in organizing the wakefulness-sleep cycle.

Security questions:

1. What are the tasks of the somatic nervous system?

2. What are the tasks of the autonomic nervous system?

3. Name the main differences between the somatic and autonomic parts of the nervous system.

4. What is the simatic nervous system?

5. How does increased activity of the sympathetic nervous system manifest itself?

6. What is the parasimatic nervous system?

7. How does increased activity of the parasympathetic nervous system manifest itself?

8. What is homeostasis?

9. Which centers control the activity of the sympathetic system, and which – the parasympathetic?

10. Is it true that the somatic and autonomic parts of the nervous system act completely independently of each other? Give reasons for your answer.

Topic 8. NEUROENDOCRINE SYSTEM

Endocrine, or according to modern data, neuroendocrine system regulates and coordinates the activity of all organs and systems, ensuring the body’s adaptation to constantly changing factors of the external and internal environment, resulting in the preservation of homeostasis, which, as is known, is necessary to maintain the normal functioning of the body. In recent years, it has been clearly shown that the neuroendocrine system performs the listed functions in close interaction with the immune system.

Guidelines

The endocrine system is represented endocrine glands, responsible for the formation and release of various hormones into the blood.

It has been established that the central nervous system (CNS) takes part in the regulation of the secretion of hormones from all endocrine glands, and hormones, in turn, influence the function of the CNS, modifying its activity and condition. Nervous regulation of the body’s endocrine functions is carried out both through hypophysiotropic (hypothalamic) hormones and through the influence of the autonomic (autonomic) nervous system. In addition, a sufficient amount of monoamines and peptide hormones are secreted in various areas of the central nervous system, many of which are also secreted in the endocrine cells of the gastrointestinal tract.

Endocrine function of the body provide systems that include: endocrine glands that secrete hormones; hormones and their transport pathways, corresponding organs or target tissues that respond to the action of hormones and are provided by normal receptor and post-receptor mechanisms.

The endocrine system of the body as a whole maintains the constancy in the internal environment necessary for the normal course of physiological processes. In addition, the endocrine system, together with the nervous and immune systems, ensures reproductive function, growth and development of the body, formation, utilization and storage (“in reserve” in the form of glycogen or fatty tissue) of energy.

Mechanism of action of hormones

Hormone is a biologically active substance. This is a chemical informative signal that can cause rapid changes in the cell. The hormone, like other informative signals, is bound by cell membrane receptors. But unlike those signals that open ion channels in the membrane, the hormone “turns on” a chain (cascade) of chemical reactions that begin on the upper surface of the membrane, continue on its inner surface, and end deep inside the cell. One of the links in this chain of reactions are the so-called second messengers. Second intermediaries- These are “biological amplifiers” of biochemical processes. In all living organisms, from humans to single-celled organisms, only two second messengers are known: cyclic adenosine monophosphoric acid (CAMP) and inositol triphosphate (IF-3). The second mediators also include calcium (Ca). Thus, the second messenger is an intermediary in the transmission of an informative signal from the hormone to the internal systems of the cell. ( The first intermediaries- these are synaptic mediators known to us).

In the life of animals and humans, from time to time a state of psycho-emotional stress arises. It arises under the influence of three factors: the uncertainty of the situation (it is difficult to determine the probability of events, it is difficult to make a decision), lack of time, the significance of the situation (to satisfy hunger or save a life?).

Psycho-emotional stress (stress) is accompanied by both subjective experiences and physiological changes in all body systems: cardiovascular, muscular, endocrine.

At the onset of stress, the hypothalamus, through a nerve conduction pathway (sympathetic nervous system, nerve impulse), stimulates the release of adrenaline (anxiety hormone) from the adrenal glands. Adrenaline enhances the nutrition of muscles and the brain: it transfers fatty acids from fat depots into the blood (to nourish the muscles), and from liver glycogen it transfers glucose into the blood (to nourish the brain). But this is not energetically beneficial for the body during prolonged stress, because the muscle can “eat” glucose without leaving it for the brain.

Therefore, at the next stage of stress, the pituitary gland releases ACTH (adrenocorticotropic hormone) and stimulates the release of cortisol from the adrenal cortex. Cortisol interferes with the absorption of glucose into muscle tissue. In addition, cortisol activates the conversion of protein into glucose. This is important because glycogen stores are low. But where does protein come from? (Remember that during stress, all digestion processes are inhibited). The body has a lot of structural protein - all cells are made of protein. But if you transfer it to “fuel”, that is, turn it into glucose, then you can destroy the entire body. Therefore, protein is taken from those tissues of the body that are quickly renewed and which can be temporarily dispensed with. Such tissue is lymphocytes, i.e. the protective cells of the body. Their protein is converted into glucose. But such an escape from stress has negative side effects, namely, after prolonged stress it is easy to get colds and viral diseases. Cortisol inhibits the activity of the “sexual” centers of the hypothalamus. Therefore, with prolonged stress (negative emotions), women experience menstrual irregularities, and men experience impaired sexual potency.

Security questions:

1. What processes is the neuroendocrine system responsible for?

2. What does the neuroendocrine system consist of?

3. What groups are glands divided into and on what basis?

4. Define the concept of “hormone” and describe the mechanism of action of hormones.

5. Name the factors contributing to the emergence of a state of psycho-emotional stress.

6. Describe the hormonal mechanism of stress.

Test assignments

1. Subject and methods of research of Higher Nervous Activity (HNA). The doctrine of the characteristics of GNI in humans and animals.

2. The human brain as a system of systems. Types of brain activity. The main functions of the human brain in the process of its phylogenesis.

3. Nervous system, anatomical structure, sections and types, nerve connections, sources of energy formation for information transmission.

4. Brain structure, regions, parts of the brain: thalamus, hypothalamus, diencephalon, their topography, functional connections.

5. Organization of the nervous system. The structure of neurons, its functions. Neural connections in information transmission. Assistive systems.

6. The concept of “synapse”, its function and role in the transmission of information. Features of synapses at different levels of nerve connections.

7. Glial cells serving neurons, their role and functions in serving the entire central nervous system. Formation of pathways in the transmission of information.

8. Classification of nerve centers according to their functional characteristics. Afferent and efferent sections. They differ in communication functions.

9. Integrated activity of the spinal and medulla oblongata. Topography, structure, functions.

10. Integrated activity of the midbrain, activity of the cerebellum. Structure, topography, neural connections.

11. Integrated activity of the cerebral cortex. Frontal, occipital, parietal areas, right and left hemispheres, the main differences in their processing of information.

12. Physiological properties of the autonomic nervous system. Her participation in emotional reactions. Sympathetic and parasympathetic divisions of the autonomic nervous system.

13. Reticular formation, its topography, influence on brain activity, connection with other areas of the brain. Controlling role in the transfer of information.

14. Conducting nervous stimulation in the body. The property of nerve fibers in conducting and transmitting information, the systemic organization of pathways. Conducting pathways of the brain and spinal cord.

15. Features and conditions that form the synaptic transmission of information, stages and mechanisms of synaptic transmission. Features of synaptic connections of the brain, spinal cord, visceral system.

16. Fundamental principles of the theory of reflex activity. Conditioned and unconditioned (innate) reflexes. Difference between conditioned and unconditioned reflexes.

17. Processing of information in the central nervous system. The concept of "sensory system". The structure of connections that form sensory systems.

18. Conversion and transmission of signals to the sensory system. Receptor sensitivity. Coding of stimuli in the sensory system.

19. The structure of the visual analyzer, its physiological characteristics. Pathways for transmitting visual information to brain centers.

20. Visual reflexes: accommodation, photoreception. Features of the structure of the retina. Characteristics of photoreceptors.

21. Central visual pathways. Activity of the visual cortex. Technology of formation and transmission of visual information. Reaction of the cortex to visual drainage.

22. Anatomy and physiology of the hearing organs. Auditory system. Central auditory pathways. Characteristics of neurons that form sound perceptions.

23. Vestibular system (balance apparatus). Features of hair cells in the balance apparatus. Conducting system and centers of balance in the cortex.

24. General principles of the functioning of the body: correlation, regulation, self-regulation, reflex activity.

25. Functional systems. General systems theory. The concepts of “systemogenesis”, “system quantization”. Development of systems in phylogenesis.

26. Nervous regulation of the functions of internal organs. Hormonal regulation of physiological functions. Causes of hormonal regulation disorders.

27. Physiology of motor activity. Concepts, definitions. Features of motor activity in conditions of changing irritating factors. The role of motivating factors in the implementation of activity, the phenomenon of efferentation.

28. “Motor cortex”, its functions, topography. Classification of movements. Orientation and manipulation movements. Nervous pathways in the formation of motor reactions.

29. Mechanisms of initiation of motor acts. Emotional and cognitive brain, role in efferent reactions.

30. Thermoregulation of the body. Basic concepts. The body's response to external temperature. The influence of temperature on the human body. Regulators of temperature reactions.

31. Systemic mechanisms in the regulation of body temperature. Individual characteristics of reactions to temperature conditions. Daily fluctuations in body temperature.

32. Localization, features, properties of thermostats. Heat generation and heat transfer in various conditions of the body. Neuroregulation of heat.

33. Body fluids. Functions of water in the human body. Biological functions of water. The main “water depots” in the body.

34. Methods for determining liquid media in the body. Electrolyte composition of liquid media. Sources of entry and routes of release of water and electrolytes.

35. Blood as the main liquid medium. Hematopoietic organs and processes of destruction of blood elements. Blood composition, main depots. The “working” blood volume is normal.

36. Blood coagulation, hemostasis mechanisms. Fibrinolysis (dissolution) of blood. Causes and its consequences.

37. Transcellular (intercellular) fluids, composition, functions. The role of intercellular fluid in ensuring optimal turgor of the human body.

38. Osmotic pressure of tissues and organs (osmolality), tonicity of solutions. Causes of osmotic pressure disturbances, consequences for the body.

39. Metabolism and energy in the body. Types of metabolism, stages, phenomena of anabolism and catabolism. Metabolic disorders and their consequences for the body.

40. Mineral metabolism in the body, ionic composition of liquids. The physiological role of potassium, calcium, magnesium and other elements in mineral metabolism. Consequences of mineral metabolism disorders.

41. Metabolism of fats, their biological role, heat capacity, participation in metabolism. Energy value of fats. Fat deposits.

42. Metabolism of carbohydrates, mechanism of absorption, role in maintaining life, products of carbohydrate oxidation, energy cost. Consequences of excess carbohydrate deposition.

44. Thermodynamics of living systems. Factors influencing the formation, accumulation and consumption of thermal energy. Efficiency of a living cell. Heat limits in various tissues of the body.

45. Heat consumption in the body. Basic metabolism and energy expenditure. The influence of activities on energy expenditure. Acceptable limits of overheating and hypothermia of tissues and organs.

46. ​​Functional asymmetry of the brain. Types of asymmetry by nature of manifestation, functional asymmetries. The role of asymmetry in the formation of individual functions.

47. Morphological asymmetry of the cerebral hemispheres. Forms of joint activity of the hemispheres: integration of information, control functions, interhemispheric transfer of information.

48. Left-handedness and right-handedness in brain activity. Origin of left-handedness. Types of left-handedness. Age-related features of the formation of left-handedness.

49. Information processing blocks in the central nervous system. Formation of blocks, their structures, actual nerve centers, their “support” connections in information processing.

50. Receptors as the main “receivers” of information from the external and internal environments. Information transmission systems that receive receptors. Reception levels by function.

51. The concept of “analyzers”. Their functions, specificity. Connections between analyzers. The principle of “divergence” and “convergence” in supporting the adoption of specific actions in response to the influence of a stimulus.

52. Level centers of the cerebral cortex. Primary, secondary and tertiary zone of the cortex. Functional features of each of these zones.

53. Block of regulation of tone and wakefulness in the cortex as a modeling system of the brain. The functions performed by this block, the connection with the reticular formation as a controlling system.

54. Block of programming, regulation and control of complex forms of activity. Functions of the motor analyzer, areas of the motor cortex. Neural network of motor analyzers.

55. Functional organization of the motor cortex. Motor pathways of the brain (pyramidal tract). Formation of motor programs for information transfer.

56. Structure of the spine. Departments, quantity and quality of vertebrae. The cross-sectional size of different parts of the vertebrae. "Styling" and protecting the spinal cord from damage.

57. Structures and functions of the spinal cord: topography, structure, dimensions. Nerve nuclei of the spinal cord, nerve afferent and efferent pathways.

58. White and gray matter of the spinal cord. Functions of individual sections of the gray matter of the spinal cord. Spinal nerves, their functions, topography of nerve trunks, their “service areas”.

59. Medulla oblongata. Internal structure, functions. Characteristics and functions of nuclei and exiting nerves. The structure of the information they process.

60. Hindbrain. Structure (pons, cerebellum). Outgoing nerves, nuclei, their role in the perception and processing of information, “controlling function”.

61. Midbrain and diencephalon. Structure and functions of the thalamus (visual thalamus). Nuclear neurons as centers for storing and processing information.

62. Telencephalon. Cerebral cortex, cortical lobes, right and left hemispheres, sulci. The role of the corpus callosum in the functional activity of the cerebral cortex.

LITERATURE

1. Anatomy. Physiology. Human psychology: a brief illustrated dictionary / ed. acad. . – St. Petersburg. : Peter, 2001. – 256 p.

2. Human anatomy. In 2 hours. Part 2 / ed. . – M.: Medicine, 1993. – 549 p.

3. Anokhin, and the neurophysiology of the conditioned reflex /. – M.: Medicine, 1968. – 547 p.

4. Danilova,: textbook. for universities/ . – M.: Aspect-Press. 2002. – 373 p.

5. Pribram, K. Languages ​​of the brain / K. Pribram. – M.: Progress, 1975. – 464 p.

6. Sokolov, and the conditioned reflex. New look / . – M.: Moscow Psychological and Social Institute. 2003. – 287 p.

7. Physiology. Fundamentals and functional systems: a course of lectures / ed. . – M.: “Science”, 2000. – 784 p.

Holy plan 2011, pos. 19

Educational edition

Parkhomenko Daria Alexandrovna

ANATOMY AND PHYSIOLOGY

CENTRAL NERVOUS SYSTEM

Methodical manual

for students of specialty 1 – “Engineering and psychological support of information technologies”

correspondence courses

Editor

Corrector

Signed for printing Format 60x84 /16 Offset paper

Typeface "Times" Printed on a risograph Cond. oven l.

Academic ed. l. 1.6 Circulation 100 Order 48

Publisher and printing:

Educational institution

The main part of the nervous system of vertebrates and humans is the central nervous system. It is represented by the brain and spinal cord and consists of many clusters of neurons and their processes. The central nervous system performs many important functions, the main one of which is the implementation of various reflexes.

What is the CNS?

As we evolved, the regulation and coordination of all vital processes of the body began to occur at a completely new level. Improved mechanisms began to provide a very fast response to any changes in the external environment. In addition, they began to remember impacts on the body that occurred in the past, and, if necessary, retrieve this information. Similar mechanisms formed the nervous system that appeared in humans and vertebrates. It is divided into central and peripheral.

So what is the CNS? This is the main department that not only unites, but also coordinates the work of all organs and systems, and also ensures continuous interaction with the external environment and maintains normal mental activity.

Structural unit

A similar path includes:

  • sensory receptor;
  • afferent, associative, efferent neurons;
  • effector

All reactions are divided into 2 types:

  • unconditional (innate);
  • conditional (acquired).

The nerve centers of a large number of reflexes are located in the central nervous system, but the reactions, as a rule, are closed outside its boundaries.

Coordination activities

This is the most important function of the central nervous system, implying the regulation of the processes of inhibition and excitation in the structures of neurons, as well as the implementation of responses.

Coordination is necessary for the body to perform complex movements that involve numerous muscles. Examples: performing gymnastic exercises; speech accompanied by articulation; the process of swallowing food.

Pathologies

It is worth noting that the central nervous system is a system whose dysfunction negatively affects the functioning of the entire organism. Any failure poses a health hazard. Therefore, when the first alarming symptoms appear, you should consult a doctor.

The main types of central nervous system diseases are:

  • vascular;
  • chronic;
  • hereditary;
  • infectious;
  • received as a result of injuries.

Currently, about 30 pathologies of this system are known. The most common diseases of the central nervous system include:

  • insomnia;
  • Alzheimer's disease;
  • cerebral palsy;
  • Parkinson's disease;
  • migraine;
  • lumbago;
  • meningitis;
  • myasthenia gravis;
  • ischemic stroke;
  • neuralgia;
  • multiple sclerosis;
  • encephalitis.

Pathologies of the central nervous system arise as a result of lesions in any of its departments. Each of the ailments has unique symptoms and requires an individual approach to choosing a treatment method.

In conclusion

The task of the central nervous system is to ensure the coordinated functioning of each cell of the body, as well as its interaction with the outside world. Brief description of the central nervous system: it is represented by the brain and spinal cord, its structural unit is the neuron, and the main principle of its activity is reflex. Any disturbances in the functioning of the central nervous system inevitably lead to disruptions in the functioning of the entire body.

It consists of the thalamus, epithalamus, metathalamus and hypothalamus. ascending fibers from the hypothalamus from the raphe nuclei of the locus coeruleus of the reticular formation of the brain stem and partially from the spinothalamic tracts as part of the medial lemniscus. Hypothalamus General structure and location of the hypothalamus.


Share your work on social networks

If this work does not suit you, at the bottom of the page there is a list of similar works. You can also use the search button


Introduction

Thalamus (visual thalamus)

Hypothalamus

Conclusion

References


Introduction

For a modern psychologist, the anatomy of the central nervous system is the basic layer of psychological knowledge. Without an understanding of the physiological functioning of the brain, it is impossible to qualitatively study mental processes and phenomena, as well as understand their essence.

Speaking about the thalamus and hypothalamus, we should first talk aboutdiencephalon(diencephalon ). The diencephalon is located above the midbrain, under the corpus callosum. It consists of the thalamus, epithalamus, metathalamus and hypothalamus. At the base of the brain, its anterior border runs along the anterior surface of the optic chiasm, the anterior edge of the posterior perforated substance and optic tracts, and posteriorly along the edge of the cerebral peduncles. On the dorsal surface, the anterior border is the terminal strip separating the diencephalon from the telencephalon, and the posterior border is the groove separating the diencephalon from the superior colliculi of the midbrain. In a sagittal section, the diencephalon is visible under the corpus callosum and fornix.

The cavity of the diencephalon is III ventricle, which communicates through the right and left interventricular foramina with the lateral ventricles located inside the cerebral hemispheres and through the cerebral aqueduct with the cavity IV cerebral ventricle. On the top wall III In the ventricle there is a choroid plexus, which, along with plexuses in other ventricles of the brain, participates in the formation of cerebrospinal fluid.

The thalamic brain is divided into paired formations:

thalamus ( thalamus);

metathalamus (zathalamic region);

epithalamus (suprathalamic region);

subthalamus (subthalamic region).

The metathalamus (zathalamic region) is formed by pairedmedial and lateral geniculate bodieslocated behind each thalamus. The geniculate bodies contain nuclei in which impulses going to the cortical sections of the visual and auditory analyzers are switched.

The medial geniculate body is located behind the thalamic cushion; together with the lower colliculi of the midbrain roof plate, it is the subcortical center of the auditory analyzer.

The lateral geniculate body is located inferior to the thalamic cushion. Together with the superior colliculus, it forms the subcortical center of the visual analyzer.

Epithalamus (suprathalamic region) includespineal body (epiphysis), leashes and triangles of leashes. The triangles of the leashes contain nuclei related to the olfactory analyzer. The leashes extend from the triangles of the leashes, go caudally, are connected by a commissure and pass into the pineal gland. The latter is, as it were, suspended on them and is located between the upper tubercles of the quadrigeminal. The pineal gland is an endocrine gland. Its functions have not been fully established; it is assumed that it regulates the onset of puberty.


Thalamus (visual thalamus)

General structure and location of the thalamus.

Thalamus, or thalamus, is a paired ovoid formation with a volume of about 3.3 cm 3 , consisting mainly of gray matter (clusters of numerous nuclei). Thalami are formed due to thickening of the lateral walls of the diencephalon. In front, the pointed part of the thalamus formsanterior tubercle,in which the intermediate centers of sensory (afferent) pathways running from the brain stem to the cerebral cortex are located. Posterior, expanded and rounded part of the thalamus - pillow - contains the subcortical visual center.

Figure 1 . Diencephalon in sagittal section.

The thickness of the gray matter of the thalamus is divided vertically Y -shaped layer (plate) of white matter into three parts - anterior, medial and lateral.

Medial surface of the thalamusclearly visible on the sagittal (sagittal - sagittal (lat. " sagitta" - arrow), dividing into symmetrical right and left halves) in a section of the brain (Fig. 1). The medial (i.e., located closer to the middle) surface of the right and left thalamus, facing each other, form the lateral walls III cerebral ventricle (diencephalon cavity) in the middle they are connected to each otherinterthalamic fusion.

Anterior (inferior) surface of the thalamusfused with the hypothalamus, through it, from the caudal side (i.e., located closer to the lower part of the body), pathways from the cerebral peduncles enter the diencephalon.

Lateral (i.e. side) surface thalamus borders oninternal capsule -a layer of white matter of the cerebral hemispheres, consisting of projection fibers connecting the cerebral cortex with the underlying brain structures.

Each of these parts of the thalamus contains several groupsthalamic nuclei. In total, the thalamus contains from 40 to 150 specialized nuclei.

Functional significance of the thalamic nuclei.

According to topography, the thalamic nuclei are divided into 8 main groups:

1. anterior group;

2. mediodorsal group;

3. group of midline nuclei;

4. dorsolateral group;

5. ventrolateral group;

6. ventral posteromedial group;

7. posterior group (nuclei of the thalamic cushion);

8. intralaminar group.

The nuclei of the thalamus are divided into sensory ( specific and nonspecific),motor and associative. Let us consider the main groups of thalamic nuclei necessary to understand its functional role in the transmission of sensory information to the cerebral cortex.

Located in the anterior part of the thalamus front group thalamic nuclei (Fig.2). The largest of them areanteroventral core and anteromedialcore. They receive afferent fibers from the mammillary bodies, the olfactory center of the diencephalon. Efferent fibers (descending, i.e. carrying impulses from the brain) from the anterior nuclei are directed to the cingulate gyrus of the cerebral cortex.

The anterior group of thalamic nuclei and associated structures are an important component of the limbic system of the brain, which controls psycho-emotional behavior.

Rice. 2 . Topography of thalamic nuclei

In the medial part of the thalamus there aremediodorsal nucleus And group of midline nuclei.

Mediodorsal nucleushas bilateral connections with the olfactory cortex of the frontal lobe and the cingulate gyrus of the cerebral hemispheres, the amygdala and the anteromedial nucleus of the thalamus. Functionally, it is also closely connected with the limbic system and has bilateral connections with the parietal, temporal and insular cortex of the brain.

The mediodorsal nucleus is involved in the implementation of higher mental processes. Its destruction leads to a decrease in anxiety, anxiety, tension, aggressiveness, and the elimination of obsessive thoughts.

Midline nucleiare numerous and occupy the most medial position in the thalamus. They receive afferent (i.e., ascending) fibers from the hypothalamus, from the raphe nuclei, the locus coeruleus of the reticular formation of the brain stem, and partly from the spinothalamic tracts as part of the medial lemniscus. Efferent fibers from the midline nuclei are sent to the hippocampus, amygdala and cingulate gyrus of the cerebral hemispheres, which are part of the limbic system. Connections with the cerebral cortex are bilateral.

The midline nuclei play an important role in the processes of awakening and activation of the cerebral cortex, as well as in supporting memory processes.

In the lateral (i.e. lateral) part of the thalamus there aredorsolateral, ventrolateral, ventral posteromedial And posterior group of nuclei.

Nuclei of the dorsolateral grouprelatively little studied. They are known to be involved in the pain perception system.

Nuclei of the ventrolateral groupanatomically and functionally differ from each other.Posterior nuclei of the ventrolateral groupoften considered as one ventrolateral nucleus of the thalamus. This group receives fibers from the ascending tract of general sensitivity as part of the medial lemniscus. Fibers of taste sensitivity and fibers from the vestibular nuclei also come here. Efferent fibers starting from the nuclei of the ventrolateral group are sent to the cortex of the parietal lobe of the cerebral hemispheres, where they carry somatosensory information from the whole body.

TO posterior group nuclei(nucleus of the thalamic cushion) there are afferent fibers from the superior colliculi and fibers in the optic tracts. Efferent fibers are widely distributed in the cortex of the frontal, parietal, occipital, temporal and limbic lobes of the cerebral hemispheres.

The nuclear centers of the thalamic cushion are involved in the complex analysis of various sensory stimuli. They play a significant role in the perceptual (related to perception) and cognitive (cognitive, thinking) activity of the brain, as well as in memory processes - storing and reproducing information.

Intralaminar group of nucleithe thalamus lies in the thickness of the vertical Y -shaped layer of white matter. The intralaminar nuclei are interconnected with the basal ganglia, the dentate nucleus of the cerebellum and the cerebral cortex.

These nuclei play an important role in the activation system of the brain. Damage to the intralaminar nuclei in both thalami leads to a sharp decrease in motor activity, as well as apathy and destruction of the motivational structure of the personality.

The cerebral cortex, thanks to bilateral connections with the nuclei of the thalamus, is capable of exerting a regulatory effect on their functional activity.

Thus, the main functions of the thalamus are:

processing of sensory information from receptors and subcortical switching centers with its subsequent transfer to the cortex;

participation in the regulation of movements;

ensuring communication and integration of different parts of the brain.

Hypothalamus

General structure and location of the hypothalamus.

Hypothalamus ) represents the ventral section (i.e., abdominal) of the diencephalon. It consists of a complex of formations located under III ventricle The hypothalamus is limited anteriorlyvisual cross (chiasm), laterally - the anterior part of the subthalamus, the internal capsule and the optic tracts extending from the chiasm. Posteriorly, the hypothalamus continues into the tegmentum of the midbrain. The hypothalamus includesmastoid bodies, gray tubercle and optic chiasm. Mastoid bodieslocated on the sides of the midline anterior to the posterior perforated substance. These are formations of irregular spherical shape, white. Anterior to the gray tubercle is locatedoptic chiasm. In it, a transition occurs to the opposite side of part of the optic nerve fibers coming from the medial half of the retina. After the decussation, the optic tracts are formed.

Gray hillock located anterior to the mastoid bodies, between the optic tracts. The gray tubercle is a hollow protrusion of the lower wall III ventricle, formed by a thin plate of gray matter. The apex of the gray mound is elongated into a narrow hollow funnel , at the end of which is pituitary gland [ 4; 18].

Pituitary gland: structure and functioning

Pituitary (hypophysis) - an endocrine gland, it is located in a special depression at the base of the skull, the “sella turcica” and is connected to the base of the brain with the help of a pedicle. The pituitary gland contains the anterior lobe (adenohypophysis - glandular pituitary gland) and the posterior lobe (neurohypophysis).

Posterior lobe, or neurohypophysis, consists of neuroglial cells and is a continuation of the hypothalamic infundibulum. Larger share - adenohypophysis, built of glandular cells. Due to the close interaction of the hypothalamus with the pituitary gland, a single system functions in the diencephalonhypothalamic-pituitary system,controlling the work of all endocrine glands, and with their help, the vegetative functions of the body (Fig. 3).

Figure 3. The pituitary gland and its influence on other endocrine glands

There are 32 pairs of nuclei in the gray matter of the hypothalamus. Interaction with the pituitary gland is carried out through neurohormones secreted by the nuclei of the hypothalamus -releasing hormones. Through the system of blood vessels they enter the anterior lobe of the pituitary gland (adenohypophysis), where they contribute to the release of tropic hormones that stimulate the synthesis of specific hormones in other endocrine glands.

In the anterior lobe of the pituitary gland tropic ones are produced hormones (thyroid-stimulating hormone - thyrotropin, adrenocorticotropic hormone - corticotropin and gonadotropic hormones - gonadotropins) and effector hormones (growth hormones - somatotropin and prolactin).

Hormones of the anterior pituitary gland

Tropic:

Thyroid-stimulating hormone (thyrotropin)stimulates thyroid function. If the pituitary gland is removed or destroyed in animals, atrophy of the thyroid gland occurs, and the administration of thyrotropin restores its functions.

Adrenocorticotropic hormone (corticotropin)stimulates the function of the zona fasciculata of the adrenal cortex, in which hormones are formedglucocorticoids.The effect of the hormone on the zona glomerulosa and reticularis is less pronounced. Removal of the pituitary gland in animals leads to atrophy of the adrenal cortex. Atrophic processes affect all zones of the adrenal cortex, but the most profound changes occur in the cells of the reticular and fascicular zones. The extra-adrenal effect of corticotropin is expressed in stimulation of lipolysis processes, increased pigmentation, and anabolic effects.

Gonadotropic hormones (gonadotropins).Follicle stimulating hormone ( follitropin) stimulates the growth of the vesicular follicle in the ovary. The effect of follitropin on the formation of female sex hormones (estrogens) is small. This hormone is present in both women and men. In men, under the influence of follitropin, the formation of germ cells (spermatozoa) occurs. Luteinizing hormone ( lutropin) necessary for the growth of the vesicular follicle of the ovary in the stages preceding ovulation, and for ovulation itself (rupture of the membrane of a mature follicle and the release of an egg from it), the formation of the corpus luteum at the site of the burst follicle. Lutropin stimulates the formation of female sex hormones - estrogens. However, in order for this hormone to exert its effect on the ovary, a preliminary long-term action of follitropin is necessary. Lutropin stimulates the production progesterone yellow body. Lutropin is available in both women and men. In men, it promotes the formation of male sex hormones - androgens.

Effector:

Growth hormone (somatotropin)stimulates body growth by enhancing protein formation. Under the influence of the growth of epiphyseal cartilages in the long bones of the upper and lower extremities, bone growth occurs in length. Growth hormone increases insulin secretion through somatomedins, formed in the liver.

Prolactin stimulates the formation of milk in the alveoli of the mammary glands. Prolactin exerts its effect on the mammary glands after the preliminary action of the female sex hormones progesterone and estrogens on them. The act of sucking stimulates the formation and release of prolactin. Prolactin also has a luteotropic effect (promotes the long-term functioning of the corpus luteum and the formation of the hormone progesterone).

Processes in the posterior lobe of the pituitary gland

The posterior lobe of the pituitary gland does not produce hormones. Inactive hormones that are synthesized in the paraventricular and supraoptic nuclei of the hypothalamus enter here.

The hormones are predominantly produced in the neurons of the paraventricular nucleus oxytocin, and in the neurons of the supraoptic nucleus -vasopressin (antidiuretic hormone).These hormones accumulate in the cells of the posterior pituitary gland, where they are converted into active hormones.

Vasopressin (antidiuretic hormone)plays an important role in the processes of urine formation and, to a lesser extent, in the regulation of blood vessel tone. Vasopressin, or antidiuretic hormone - ADH (diuresis - urine output) - stimulates the reabsorption (resorption) of water in the renal tubules.

Oxytocin (ocytonin)increases uterine contraction. Its contraction increases sharply if it was previously under the influence of the female sex hormones estrogen. During pregnancy, oxytocin does not affect the uterus, since under the influence of the corpus luteum hormone progesterone, it becomes insensitive to oxytocin. Mechanical irritation of the cervix causes the release of oxytocin reflexively. Oxytocin also has the ability to stimulate milk production. The act of sucking reflexively promotes the release of oxytocin from the neurohypophysis and the secretion of milk. In a state of stress in the body, the pituitary gland releases additional amounts of ACTH, which stimulates the release of adaptive hormones by the adrenal cortex.

Functional significance of the hypothalamic nuclei

IN anterolateral part hypothalamus is distinguished anterior and middlegroups of hypothalamic nuclei (Fig. 4).

Figure 4. Topography of the hypothalamic nuclei

The anterior group includes suprachiasmatic nuclei, preoptic nucleus,and the largest -supraoptic And paraventricular kernels.

In the nuclei of the anterior group are localized:

center of the parasympathetic division (PSNS) of the autonomic nervous system.

Stimulation of the anterior hypothalamus leads to parasympathetic reactions: constriction of the pupil, a decrease in heart rate, dilation of the lumen of blood vessels, a drop in blood pressure, increased peristalsis (i.e., wave-like contraction of the walls of hollow tubular organs, promoting the movement of their contents to the intestinal outlets);

heat transfer center. Destruction of the anterior section is accompanied by an irreversible increase in body temperature;

thirst center;

neurosecretory cells that produce vasopressin (supraoptic core) and oxytocin ( paraventricular nucleus). In neurons paraventricular And supraopticnuclei, a neurosecretion is formed, which moves along their axons to the posterior part of the pituitary gland (neurohypophysis), where it is released in the form of neurohormones -vasopressin and oxytocinentering the blood.

Damage to the anterior nuclei of the hypothalamus leads to the cessation of vasopressin release, resulting in the development ofdiabetes insipidus. Oxytocin has a stimulating effect on the smooth muscles of internal organs, such as the uterus. In general, the water-salt balance of the body depends on these hormones.

In the preoptic The nucleus produces one of the releasing hormones - luliberin, which stimulates the production of luteinizing hormone in the adenohypophysis, which controls the activity of the gonads.

Suprachiasmaticthe nuclei take an active part in the regulation of cyclical changes in the body's activity - circadian, or daily, biorhythms (for example, in the alternation of sleep and wakefulness).

To the middle group hypothalamic nuclei includedorsomedial And ventromedial nucleus, nucleus of the gray tuberosity and the core of the funnel.

In the nuclei of the middle group are localized:

center of hunger and satiety. Destructionventromedialhypothalamic nucleus leads to excess food consumption (hyperphagia) and obesity, and damagekernels of gray mound- loss of appetite and sudden weight loss (cachexia);

sexual behavior center;

center of aggression;

the center of pleasure, which plays an important role in the processes of formation of motivations and psycho-emotional forms of behavior;

neurosecretory cells that produce releasing hormones (liberins and statins), regulating the production of pituitary hormones: somatostatin, somatoliberin, luliberin, folliberin, prolactoliberin, thyreoliberin, etc. Through the hypothalamic-pituitary system they influence growth processes, the rate of physical development and puberty , the formation of secondary sexual characteristics, the functions of the reproductive system, as well as metabolism.

The middle group of nuclei controls water, fat and carbohydrate metabolism, affects blood sugar levels, the ionic balance of the body, the permeability of blood vessels and cell membranes.

Posterior part of the hypothalamus located between the gray tubercle and the posterior perforated substance and consists of the right and leftmastoid bodies.

In the posterior part of the hypothalamus, the largest nuclei are: medial and lateral nucleus, posterior hypothalamic nucleus.

In the nuclei of the posterior group are localized:

center that coordinates the activity of the sympathetic division (SNS) of the autonomic nervous system (posterior hypothalamic nucleus). Stimulation of this nucleus leads to sympathetic reactions: pupil dilation, increased heart rate and blood pressure, increased respiration and decreased tonic contractions of the intestines;

heat production center (posterior hypothalamic nucleus). Destruction of the posterior hypothalamus causes lethargy, drowsiness and decreased body temperature;

subcortical centers of the olfactory analyzer. Medial and lateral nucleusin each mastoid body they are the subcortical centers of the olfactory analyzer, and are also part of the limbic system;

neurosecretory cells that produce releasing hormones that regulate the production of pituitary hormones.


Features of the blood supply to the hypothalamus

The nuclei of the hypothalamus receive abundant blood supply. The capillary network of the hypothalamus is several times more branched than in other parts of the central nervous system. One of the features of the capillaries of the hypothalamus is their high permeability, due to the thinning of the capillary walls and their fenestration (“fenestration” - the presence of spaces - “windows” - between adjacent endothelial cells of the capillaries (from the Latin. " fenestra " - window). As a result, the blood-brain barrier (BBB) ​​is weakly expressed in the hypothalamus, and hypothalamic neurons are able to perceive changes in the composition of the cerebrospinal fluid and blood (temperature, ion content, presence and amount of hormones, etc.).

Functional significance of the hypothalamus

The hypothalamus is the central link connecting the nervous and humoral mechanisms of regulation of the autonomic functions of the body. The control function of the hypothalamus is determined by the ability of its cells to secrete and axonally transport regulatory substances, which are transferred to other structures of the brain, cerebrospinal fluid, blood or pituitary gland, changing the functional activity of target organs.

There are 4 neuroendocrine systems in the hypothalamus:

Hypothalamic-extrahypothalamic systemrepresented by neurosecretory cells of the hypothalamus, the axons of which extend into the thalamus, structures of the limbic system, and medulla oblongata. These cells secrete endogenous opioids, somatostatin, etc.

Hypothalamic-adenopituitary systemconnects the nuclei of the posterior hypothalamus with the anterior lobe of the pituitary gland. Releasing hormones (liberins and statins) are transported along this pathway. Through them, the hypothalamus regulates the secretion of tropic hormones of the adenohypophysis, which determine the secretory activity of the endocrine glands (thyroid, reproductive, etc.).

Hypothalamic-metapituitary systemconnects the neurosecretory cells of the hypothalamus with the pituitary gland. The axons of these cells transport melanostatin and melanoliberin, which regulate the synthesis of melanin, the pigment that determines the color of the skin, hair, iris and other tissues of the body.

Hypothalamic-neurohypophyseal systemconnects the nuclei of the anterior hypothalamus with the posterior (glandular) lobe of the pituitary gland. These axons transport vasopressin and oxytocin, which accumulate in the posterior lobe of the pituitary gland and are released into the bloodstream as needed.


Conclusion

Thus, the dorsal part of the diencephalon is phylogenetically youngerthalamic brain,being the highest subcortical sensory center in which almost all afferent pathways carrying sensory information from the body organs and sensory organs to the cerebral hemispheres are switched. The tasks of the hypothalamus also include the management of psycho-emotional behavior and participation in the implementation of higher mental and psychological processes, in particular memory.

Ventral section - the hypothalamus is phylogenetically older formation. The hypothalamic-pituitary system controls the humoral regulation of water-salt balance, metabolism and energy, the functioning of the immune system, thermoregulation, reproductive function, etc. Performing a regulatory role for this system, the hypothalamus is the highest center that controls the autonomic (autonomic) nervous system.


References

  1. Human Anatomy / Ed. M.R. Sapina. - M.: Medicine, 1993.
  2. Bloom F., Leiserson A., Hofstadter L. Brain, mind, behavior. - M.: Mir, 1988.
  3. Histology / Ed. V.G. Eliseeva. - M.: Medicine, 1983.
  4. Prives M.G., Lysenkov N.K., Bushkovich V.I. Human anatomy. - M.: Medicine, 1985.
  5. Sinelnikov R.D., Sinelnikov Ya.R. Atlas of human anatomy. - M.: Medicine, 1994.
  6. Tishevskaya I.A. Anatomy of the central nervous system: Textbook. - Chelyabinsk: SUSU Publishing House, 2000.

Other similar works that may interest you.vshm>
523. Functional systems of the body. Function of the nervous system 4.53 KB
Functional systems of the body. Work of the nervous system In addition to analyzers, that is, sensory systems, other systems function in the body. These systems can be clearly morphologically shaped, that is, have a clear structure. Such systems include, for example, the circulatory, respiratory or digestive systems.
11302. Features of the nervous system of a schoolchild athlete 46.21 KB
At the present stage of the country’s development, in the conditions of a qualitative transformation of all aspects of social life, the requirements for physical fitness necessary for successful work activities are increasing...
5880. Anatomy as a branch of biology│ Anatomy course of lectures 670.47 KB
Nervous tissue conducts nerve impulses arising under the influence of an internal or external stimulus and consists of: cells neurons neuroglia performs supporting trophic and protective functions Organ orgnon instrument part of the body that occupies a certain position in the body and consists of a complex of tissues united by a common function each organ performs a unique function has an individual shape structure location and species differences Organ system a group of organs interconnected anatomically having a common...
15721. China's influence on Central Asian countries and their interaction 195.28 KB
The following factors, such as close geographical location, open borders and a developed transport system, allow us to say that there are favorable preconditions for China’s growing influence in relation to the countries of Central Asia. Therefore, the study of China’s policy towards the Central Asian countries is relevant at the present time.
13735. Comprehensive assessment of soil cover in the Central zone of the Oryol region 46.49 KB
Features of the soil cover of the Oryol region. Interaction of soil formation factors on the territory of the Oryol region. The main soil combinations of the soil cover of the Central zone of the Oryol region. Comprehensive characteristics of soils in the Central zone of the Oryol region...
17360. Reflex is the basis of nervous activity. Unconditioned and conditioned reflexes and their role in the life of humans and animals 22.69 KB
The mechanisms of higher nervous activity in higher animals and humans are associated with the activity of a number of parts of the brain. The main role in these mechanisms belongs to the cerebral cortex. It has been experimentally shown that in higher representatives of the animal world, after complete surgical removal of the cortex, higher nervous activity sharply deteriorates.
13711. Anatomy and physiology, cheat sheet 94.41 KB
The development and formation of ideas about anatomy and physiology begin in ancient times (Anatomy - around 2550 BC, the ancient Egyptian Ebers papyrus "The Secret Book of the Physician"; Physiology - around the 5th century BC, Hippocrates, Aristotle, Galen) Human Anatomy – the science of the form, structure and development of the human body in connection with its function and the influence of the environment.
11025. ANATOMY AND BIOMECHANICS OF SKULL BONES 18.1 MB
The adult human skull consists of 28 bones: 8 cranial bones (occipital, sphenoid, frontal, ethmoid, temporal, parietal); 14 bones of the facial skull (vomer, maxillary, mandibular, palatine, zygomatic, lacrimal, nasal, inferior turbinates); 6 bones of a mixed group (6 bones of the inner ear. In some literature, the hyoid bone is also classified as the bones of the skull.
8275. Anatomy of the female genital organs 18.98 KB
The walls of the vagina are in contact with each other and in the upper part around the vaginal part of the cervix they form dome-shaped depressions anterior posterior right and left lateral vaults of the vagina. The upper convex part of the body is called the fundus of the uterus. The uterine cavity has the shape of a triangle in the upper corners of which the openings of the fallopian tubes open. Below, the uterine cavity narrows into the isthmus and ends with the internal os.
13726. Anatomy of the musculoskeletal system 46.36 KB
In the bone, the main place is occupied by: lamellar bone tissue, which forms a compact substance and spongy bone. Chemical composition and physical properties of bone. The surface of the bone is covered with periosteum. The periosteum is rich in nerves and blood vessels, through which nutrition and innervation of the bone is carried out.

SOCIAL-TECHNOLOGICAL INSTITUTE OF MOSCOW STATE SERVICE UNIVERSITY

ANATOMY OF THE CENTRAL NERVOUS SYSTEM

(Tutorial)

O.O. Yakimenko

Moscow - 2002


A manual on the anatomy of the nervous system is intended for students of the Socio-Technological Institute, Faculty of Psychology. The content includes basic issues related to the morphological organization of the nervous system. In addition to anatomical data on the structure of the nervous system, the work includes histological cytological characteristics of nervous tissue. As well as questions of information about the growth and development of the nervous system from embryonic to late postnatal ontogenesis.

For clarity of the presented material, illustrations are included in the text. For independent work of students, a list of educational and scientific literature, as well as anatomical atlases, is provided.

Classic scientific data on the anatomy of the nervous system are the foundation for the study of the neurophysiology of the brain. Knowledge of the morphological characteristics of the nervous system at each stage of ontogenesis is necessary to understand the age-related dynamics of human behavior and psyche.

SECTION I. CYTOLOGICAL AND HISTOLOGICAL CHARACTERISTICS OF THE NERVOUS SYSTEM

General plan of the structure of the nervous system

The main function of the nervous system is to quickly and accurately transmit information, ensuring the interaction of the body with the outside world. Receptors respond to any signals from the external and internal environment, converting them into streams of nerve impulses that enter the central nervous system. Based on the analysis of the flow of nerve impulses, the brain forms an adequate response.

Together with the endocrine glands, the nervous system regulates the functioning of all organs. This regulation is carried out due to the fact that the spinal cord and brain are connected by nerves to all organs, bilateral connections. Signals about their functional state are sent from organs to the central nervous system, and the nervous system, in turn, sends signals to the organs, correcting their functions and ensuring all vital processes - movement, nutrition, excretion and others. In addition, the nervous system ensures coordination of the activities of cells, tissues, organs and organ systems, while the body functions as a single whole.

The nervous system is the material basis of mental processes: attention, memory, speech, thinking, etc., with the help of which a person not only cognizes the environment, but can also actively change it.

Thus, the nervous system is that part of a living system that specializes in transmitting information and integrating reactions in response to environmental influences.

Central and peripheral nervous system

The nervous system is divided topographically into the central nervous system, which includes the brain and spinal cord, and the peripheral nervous system, which consists of nerves and ganglia.

Nervous system

According to the functional classification, the nervous system is divided into somatic (divisions of the nervous system that regulate the work of skeletal muscles) and autonomic (vegetative), which regulates the work of internal organs. The autonomic nervous system has two divisions: sympathetic and parasympathetic.

Nervous system

somatic autonomic

sympathetic parasympathetic

Both the somatic and autonomic nervous systems include central and peripheral divisions.

Nervous tissue

The main tissue from which the nervous system is formed is nervous tissue. It differs from other types of tissue in that it lacks intercellular substance.

Nervous tissue consists of two types of cells: neurons and glial cells. Neurons play a major role in providing all functions of the central nervous system. Glial cells have an auxiliary role, performing supporting, protective, trophic functions, etc. On average, the number of glial cells exceeds the number of neurons in a ratio of 10:1, respectively.

The meninges are formed by connective tissue, and the brain cavities are formed by a special type of epithelial tissue (epindymal lining).

Neuron is a structural and functional unit of the nervous system

A neuron has characteristics common to all cells: it has a plasma membrane, a nucleus and cytoplasm. The membrane is a three-layer structure containing lipid and protein components. In addition, on the surface of the cell there is a thin layer called glycocalis. The plasma membrane regulates the exchange of substances between the cell and the environment. This is especially important for a nerve cell, since the membrane regulates the movement of substances that are directly related to nerve signaling. The membrane also serves as the site of electrical activity that underlies rapid neural signaling and the site of action of peptides and hormones. Finally, its sections form synapses - the place of contact between cells.

Each nerve cell has a nucleus that contains genetic material in the form of chromosomes. The nucleus performs two important functions - it controls the differentiation of the cell into its final form, determining the types of connections and regulates protein synthesis throughout the cell, controlling the growth and development of the cell.

The cytoplasm of a neuron contains organelles (endoplasmic reticulum, Golgi apparatus, mitochondria, lysosomes, ribosomes, etc.).

Ribosomes synthesize proteins, some of which remain in the cell, the other part is intended for removal from the cell. In addition, ribosomes produce elements of the molecular machinery for most cellular functions: enzymes, carrier proteins, receptors, membrane proteins, etc.

The endoplasmic reticulum is a system of channels and membrane-surrounded spaces (large, flat, called cisterns, and small, called vesicles or vesicles). There are smooth and rough endoplasmic reticulum. The latter contains ribosomes

The function of the Golgi apparatus is to store, concentrate and package secretory proteins.

In addition to systems that produce and transport various substances, the cell has an internal digestive system consisting of lysosomes that do not have a specific shape. They contain a variety of hydrolytic enzymes that break down and digest a variety of compounds occurring both inside and outside the cell.

Mitochondria are the most complex organ of the cell after the nucleus. Its function is the production and delivery of energy necessary for the life of cells.

Most of the body's cells are capable of metabolizing various sugars, and energy is either released or stored in the cell in the form of glycogen. However, nerve cells in the brain use glucose exclusively, since all other substances are retained by the blood-brain barrier. Most of them lack the ability to store glycogen, which increases their dependence on blood glucose and oxygen for energy. Therefore, nerve cells have the largest number of mitochondria.

The neuroplasm contains special-purpose organelles: microtubules and neurofilaments, which differ in size and structure. Neurofilaments are found only in nerve cells and represent the internal skeleton of the neuroplasm. Microtubules stretch along the axon along the internal cavities from the soma to the end of the axon. These organelles distribute biologically active substances (Fig. 1 A and B). Intracellular transport between the cell body and the processes extending from it can be retrograde - from nerve endings to the cell body and orthograde - from the cell body to the endings.

Rice. 1 A. Internal structure of a neuron

A distinctive feature of neurons is the presence of mitochondria in the axon as an additional source of energy and neurofibrils. Adult neurons are not capable of division.

Each neuron has an extended central body - the soma and processes - dendrites and axon. The cell body is enclosed in a cell membrane and contains a nucleus and a nucleolus, maintaining the integrity of the membranes of the cell body and its processes, which ensure the conduction of nerve impulses. In relation to the processes, the soma performs a trophic function, regulating the metabolism of the cell. Impulses travel along dendrites (afferent processes) to the body of the nerve cell, and through axons (efferent processes) from the body of the nerve cell to other neurons or organs.

Most dendrites (dendron - tree) are short, highly branched processes. Their surface increases significantly due to small outgrowths - spines. An axon (axis - process) is often a long, slightly branched process.

Each neuron has only one axon, the length of which can reach several tens of centimeters. Sometimes lateral processes - collaterals - extend from the axon. The endings of the axon usually branch and are called terminals. The place where the axon emerges from the cell soma is called the axonal hillock.

Rice. 1 B. External structure of a neuron


There are several classifications of neurons based on different characteristics: the shape of the soma, the number of processes, the functions and effects that the neuron has on other cells.

Depending on the shape of the soma, granular (ganglionic) neurons are distinguished, in which the soma has a rounded shape; pyramidal neurons of different sizes - large and small pyramids; stellate neurons; fusiform neurons (Fig. 2 A).

Based on the number of processes, unipolar neurons are distinguished, having one process extending from the cell soma; pseudounipolar neurons (such neurons have a T-shaped branching process); bipolar neurons, which have one dendrite and one axon; and multipolar neurons, which have several dendrites and one axon (Fig. 2 B).

Rice. 2. Classification of neurons according to the shape of the soma and the number of processes


Unipolar neurons are located in sensory nodes (for example, spinal, trigeminal) and are associated with such types of sensitivity as pain, temperature, tactile, a sense of pressure, vibration, etc.

These cells, although called unipolar, actually have two processes that fuse near the cell body.

Bipolar cells are characteristic of the visual, auditory and olfactory systems

Multipolar cells have a varied body shape - spindle-shaped, basket-shaped, stellate, pyramidal - small and large.

According to the functions they perform, neurons are divided into: afferent, efferent and intercalary (contact).

Afferent neurons are sensory (pseudounipolar), their somas are located outside the central nervous system in ganglia (spinal or cranial). The shape of the soma is granular. Afferent neurons have one dendrite that connects to receptors (skin, muscle, tendon, etc.). Through dendrites, information about the properties of stimuli is transmitted to the soma of the neuron and along the axon to the central nervous system.

Efferent (motor) neurons regulate the functioning of effectors (muscles, glands, tissues, etc.). These are multipolar neurons, their somas have a stellate or pyramidal shape, lying in the spinal cord or brain or in the ganglia of the autonomic nervous system. Short, abundantly branching dendrites receive impulses from other neurons, and long axons extend beyond the central nervous system and, as part of the nerve, go to effectors (working organs), for example, to skeletal muscle.

Interneurons (interneurons, contact neurons) make up the bulk of the brain. They communicate between afferent and efferent neurons and process information coming from receptors to the central nervous system. These are mainly multipolar stellate-shaped neurons.


Among interneurons, neurons with long and short axons differ (Fig. 3 A, B).

The following are depicted as sensory neurons: a neuron whose process is part of the auditory fibers of the vestibulocochlear nerve (VIII pair), a neuron that responds to skin stimulation (SC). Interneurons are represented by amacrine (AmN) and bipolar (BN) cells of the retina, an olfactory bulb neuron (OLN), a locus coeruleus neuron (LPN), a pyramidal cell of the cerebral cortex (PN) and a stellate neuron (SN) of the cerebellum. A spinal cord motor neuron is depicted as a motor neuron.

Rice. 3 A. Classification of neurons according to their functions

Sensory neuron:

1 - bipolar, 2 - pseudobipolar, 3 - pseudounipolar, 4 - pyramidal cell, 5 - neuron of the spinal cord, 6 - neuron of the p. ambiguus, 7 - neuron of the nucleus of the hypoglossal nerve. Sympathetic neurons: 8 - from the stellate ganglion, 9 - from the superior cervical ganglion, 10 - from the intermediolateral column of the lateral horn of the spinal cord. Parasympathetic neurons: 11 - from the muscular plexus ganglion of the intestinal wall, 12 - from the dorsal nucleus of the vagus nerve, 13 - from the ciliary ganglion.

Based on the effect that neurons have on other cells, excitatory neurons and inhibitory neurons are distinguished. Excitatory neurons have an activating effect, increasing the excitability of the cells with which they are connected. Inhibitory neurons, on the contrary, reduce the excitability of cells, causing an inhibitory effect.

The space between neurons is filled with cells called neuroglia (the term glia means glue, the cells “glue” the components of the central nervous system into a single whole). Unlike neurons, neuroglial cells divide throughout a person's life. There are a lot of neuroglial cells; in some parts of the nervous system there are 10 times more of them than nerve cells. Macroglia cells and microglia cells are distinguished (Fig. 4).


Four main types of glial cells.

Neuron surrounded by various glial elements

1 - macroglial astrocytes

2 - oligodendrocytes macroglia

3 – microglia macroglia

Rice. 4. Macroglia and microglia cells


Macroglia include astrocytes and oligodendrocytes. Astrocytes have many processes that extend from the cell body in all directions, giving the appearance of a star. In the central nervous system, some processes end in a terminal stalk on the surface of blood vessels. Astrocytes lying in the white matter of the brain are called fibrous astrocytes due to the presence of many fibrils in the cytoplasm of their bodies and branches. In gray matter, astrocytes contain fewer fibrils and are called protoplasmic astrocytes. They serve as a support for nerve cells, provide repair to nerves after damage, isolate and unite nerve fibers and endings, and participate in metabolic processes that model the ionic composition and mediators. The assumptions that they are involved in the transport of substances from blood vessels to nerve cells and form part of the blood-brain barrier have now been rejected.

1. Oligodendrocytes are smaller than astrocytes, contain small nuclei, are more common in white matter, and are responsible for the formation of myelin sheaths around long axons. They act as an insulator and increase the speed of nerve impulses along the processes. The myelin sheath is segmental, the space between the segments is called the node of Ranvier (Fig. 5). Each of its segments, as a rule, is formed by one oligodendrocyte (Schwann cell), which, as it becomes thinner, twists around the axon. The myelin sheath is white (white matter) because the membranes of oligodendrocytes contain a fat-like substance - myelin. Sometimes one glial cell, forming processes, takes part in the formation of segments of several processes. It is assumed that oligodendrocytes carry out complex metabolic exchanges with nerve cells.


1 - oligodendrocyte, 2 - connection between the glial cell body and the myelin sheath, 4 - cytoplasm, 5 - plasma membrane, 6 - node of Ranvier, 7 - plasma membrane loop, 8 - mesaxon, 9 - scallop

Rice. 5A. Participation of oligodendrocyte in the formation of the myelin sheath

Four stages of “envelopment” of the axon (2) by a Schwann cell (1) and its wrapping with several double layers of membrane, which after compression form a dense myelin sheath, are presented.

Rice. 5 B. Scheme of formation of the myelin sheath.


The neuron soma and dendrites are covered with thin membranes that do not form myelin and constitute gray matter.

2. Microglia are represented by small cells capable of amoeboid movement. The function of microglia is to protect neurons from inflammation and infections (via the mechanism of phagocytosis - the capture and digestion of genetically foreign substances). Microglial cells deliver oxygen and glucose to neurons. In addition, they are part of the blood-brain barrier, which is formed by them and the endothelial cells that form the walls of blood capillaries. The blood-brain barrier traps macromolecules, limiting their access to neurons.

Nerve fibers and nerves

The long processes of nerve cells are called nerve fibers. Through them, nerve impulses can be transmitted over long distances up to 1 meter.

The classification of nerve fibers is based on morphological and functional characteristics.

Nerve fibers that have a myelin sheath are called myelinated (myelinated), and fibers that do not have a myelin sheath are called unmyelinated (non-myelinated).

Based on functional characteristics, afferent (sensory) and efferent (motor) nerve fibers are distinguished.

Nerve fibers extending beyond the nervous system form nerves. A nerve is a collection of nerve fibers. Each nerve has a sheath and a blood supply (Fig. 6).


1 - common nerve trunk, 2 - nerve fiber branches, 3 - nerve sheath, 4 - bundles of nerve fibers, 5 - myelin sheath, 6 - Schwann cell membrane, 7 - node of Ranvier, 8 - Schwann cell nucleus, 9 - axolemma.

Rice. 6 Structure of a nerve (A) and nerve fiber (B).

There are spinal nerves connected to the spinal cord (31 pairs) and cranial nerves (12 pairs) connected to the brain. Depending on the quantitative ratio of afferent and efferent fibers within one nerve, sensory, motor and mixed nerves are distinguished. In sensory nerves, afferent fibers predominate, in motor nerves, efferent fibers predominate, in mixed nerves, the quantitative ratio of afferent and efferent fibers is approximately equal. All spinal nerves are mixed nerves. Among the cranial nerves, there are three types of nerves listed above. I pair - olfactory nerves (sensitive), II pair - optic nerves (sensitive), III pair - oculomotor (motor), IV pair - trochlear nerves (motor), V pair - trigeminal nerves (mixed), VI pair - abducens nerves ( motor), VII pair - facial nerves (mixed), VIII pair - vestibulo-cochlear nerves (mixed), IX pair - glossopharyngeal nerves (mixed), X pair - vagus nerves (mixed), XI pair - accessory nerves (motor), XII pair - hypoglossal nerves (motor) (Fig. 7).


I - para-olfactory nerves,

II - para-optic nerves,

III - para-oculomotor nerves,

IV - paratrochlear nerves,

V - pair - trigeminal nerves,

VI - para-abducens nerves,

VII - parafacial nerves,

VIII - para-cochlear nerves,

IX - paraglossopharyngeal nerves,

X - pair - vagus nerves,

XI - para-accessory nerves,

XII - para-1,2,3,4 - roots of the upper spinal nerves.

Rice. 7, Diagram of the location of the cranial and spinal nerves

Gray and white matter of the nervous system

Fresh sections of the brain show that some structures are darker - this is the gray matter of the nervous system, and other structures are lighter - the white matter of the nervous system. The white matter of the nervous system is formed by myelinated nerve fibers, the gray matter by the unmyelinated parts of the neuron - somas and dendrites.

The white matter of the nervous system is represented by central tracts and peripheral nerves. The function of white matter is the transmission of information from receptors to the central nervous system and from one part of the nervous system to another.

The gray matter of the central nervous system is formed by the cerebellar cortex and the cerebral cortex, nuclei, ganglia and some nerves.

Nuclei are accumulations of gray matter in the thickness of white matter. They are located in different parts of the central nervous system: in the white matter of the cerebral hemispheres - subcortical nuclei, in the white matter of the cerebellum - cerebellar nuclei, some nuclei are located in the diencephalon, midbrain and medulla oblongata. Most nuclei are nerve centers that regulate one or another function of the body.

Ganglia are a collection of neurons located outside the central nervous system. There are spinal, cranial ganglia and ganglia of the autonomic nervous system. Ganglia are formed predominantly by afferent neurons, but they may include intercalary and efferent neurons.

Interaction of neurons

The place of functional interaction or contact of two cells (the place where one cell influences another cell) was called a synapse by the English physiologist C. Sherrington.

Synapses are peripheral and central. An example of a peripheral synapse is the neuromuscular synapse, where a neuron makes contact with a muscle fiber. Synapses in the nervous system are called central synapses when two neurons come into contact. There are five types of synapses, depending on what parts the neurons are in contact with: 1) axo-dendritic (the axon of one cell contacts the dendrite of another); 2) axo-somatic (the axon of one cell contacts the soma of another cell); 3) axo-axonal (the axon of one cell contacts the axon of another cell); 4) dendro-dendritic (the dendrite of one cell is in contact with the dendrite of another cell); 5) somo-somatic (the somas of two cells are in contact). The bulk of contacts are axo-dendritic and axo-somatic.

Synaptic contacts can be between two excitatory neurons, two inhibitory neurons, or between an excitatory and an inhibitory neuron. In this case, the neurons that have an effect are called presynaptic, and the neurons that are affected are called postsynaptic. The presynaptic excitatory neuron increases the excitability of the postsynaptic neuron. In this case, the synapse is called excitatory. The presynaptic inhibitory neuron has the opposite effect - it reduces the excitability of the postsynaptic neuron. Such a synapse is called inhibitory. Each of the five types of central synapses has its own morphological features, although the general scheme of their structure is the same.

Synapse structure

Let us consider the structure of a synapse using the example of an axo-somatic one. The synapse consists of three parts: the presynaptic terminal, the synaptic cleft and the postsynaptic membrane (Fig. 8 A, B).

A-Synaptic inputs of a neuron. Synaptic plaques at the endings of presynaptic axons form connections on the dendrites and body (soma) of the postsynaptic neuron.

Rice. 8 A. Structure of synapses

The presynaptic terminal is the extended part of the axon terminal. The synaptic cleft is the space between two neurons in contact. The diameter of the synaptic cleft is 10-20 nm. The membrane of the presynaptic terminal facing the synaptic cleft is called the presynaptic membrane. The third part of the synapse is the postsynaptic membrane, which is located opposite the presynaptic membrane.

The presynaptic terminal is filled with vesicles and mitochondria. The vesicles contain biologically active substances - mediators. Mediators are synthesized in the soma and transported via microtubules to the presynaptic terminal. The most common mediators are adrenaline, norepinephrine, acetylcholine, serotonin, gamma-aminobutyric acid (GABA), glycine and others. Typically, a synapse contains one of the transmitters in greater quantities compared to other transmitters. Synapses are usually designated by the type of mediator: adrenergic, cholinergic, serotonergic, etc.

The postsynaptic membrane contains special protein molecules - receptors that can attach molecules of mediators.

The synaptic cleft is filled with intercellular fluid, which contains enzymes that promote the destruction of neurotransmitters.

One postsynaptic neuron can have up to 20,000 synapses, some of which are excitatory, and some are inhibitory (Fig. 8 B).

B. Scheme of transmitter release and processes occurring in a hypothetical central synapse.

Rice. 8 B. Structure of synapses

In addition to chemical synapses, in which neurotransmitters are involved in the interaction of neurons, electrical synapses are found in the nervous system. In electrical synapses, the interaction of two neurons is carried out through biocurrents. The central nervous system is dominated by chemical stimuli.

In some interneuron synapses, electrical and chemical transmission occurs simultaneously - this is a mixed type of synapse.

The influence of excitatory and inhibitory synapses on the excitability of the postsynaptic neuron is summed up and the effect depends on the location of the synapse. The closer the synapses are located to the axonal hillock, the more effective they are. On the contrary, the further the synapses are located from the axonal hillock (for example, at the end of dendrites), the less effective they are. Thus, synapses located on the soma and axonal hillock influence the excitability of the neuron quickly and efficiently, while the influence of distant synapses is slow and smooth.

Neural networks

Thanks to synaptic connections, neurons are united into functional units - neural networks. Neural networks can be formed by neurons located at a short distance. Such a neural network is called local. In addition, neurons remote from each other from different areas of the brain can be combined into a network. The highest level of organization of neuronal connections reflects the connection of several areas of the central nervous system. This neural network is called by or system. There are descending and ascending paths. Along ascending pathways, information is transmitted from underlying areas of the brain to higher ones (for example, from the spinal cord to the cerebral cortex). Descending tracts connect the cerebral cortex with the spinal cord.

The most complex networks are called distribution systems. They are formed by neurons in different parts of the brain that control behavior, in which the body as a whole participates.

Some nerve networks provide convergence (convergence) of impulses on a limited number of neurons. Nervous networks can also be built according to the type of divergence (divergence). Such networks enable the transmission of information over considerable distances. In addition, neural networks provide integration (summarization or generalization) of various types of information (Fig. 9).

Rice. 9. Nervous tissue.

A large neuron with many dendrites receives information through a synaptic contact with another neuron (top left). The myelinated axon forms a synaptic contact with the third neuron (bottom). The surfaces of neurons are shown without the glial cells that surround the process towards the capillary (top right).


Reflex as the basic principle of the nervous system

One example of a nerve network would be a reflex arc, which is necessary for a reflex to occur. THEM. In 1863, Sechenov, in his work “Reflexes of the Brain,” developed the idea that the reflex is the basic principle of operation not only of the spinal cord, but also of the brain.

A reflex is the body's response to irritation with the participation of the central nervous system. Each reflex has its own reflex arc - the path along which excitation passes from the receptor to the effector (executive organ). Any reflex arc includes five components: 1) a receptor - a specialized cell designed to perceive a stimulus (sound, light, chemical, etc.), 2) an afferent pathway, which is represented by afferent neurons, 3) a section of the central nervous system , represented by the spinal cord or brain; 4) the efferent pathway consists of axons of efferent neurons extending beyond the central nervous system; 5) effector - working organ (muscle or gland, etc.).

The simplest reflex arc includes two neurons and is called monosynaptic (based on the number of synapses). A more complex reflex arc is represented by three neurons (afferent, intercalary and efferent) and is called three-neuron or disynaptic. However, most reflex arcs include a large number of interneurons and are called polysynaptic (Fig. 10 A, B).

Reflex arcs can pass through the spinal cord only (withdrawing the hand when touching a hot object) or through the brain only (closing the eyelids when a stream of air is directed at the face), or through both the spinal cord and the brain.


Rice. 10A. 1 - intercalary neuron; 2 - dendrite; 3 - neuron body; 4 - axon; 5 - synapse between sensory and interneurons; 6 - axon of a sensitive neuron; 7 - body of a sensitive neuron; 8 - axon of a sensitive neuron; 9 - axon of a motor neuron; 10 - body of the motor neuron; 11 - synapse between intercalary and motor neurons; 12 - receptor in the skin; 13 - muscle; 14 - sympathetic gaglia; 15 - intestine.

Rice. 10B. 1 - monosynaptic reflex arc, 2 - polysynaptic reflex arc, 3K - posterior root of the spinal cord, PC - anterior root of the spinal cord.

Rice. 10. Scheme of the structure of the reflex arc


Reflex arcs are closed into reflex rings using feedback connections. The concept of feedback and its functional role was indicated by Bell in 1826. Bell wrote that two-way connections are established between the muscle and the central nervous system. With the help of feedback, signals about the functional state of the effector are sent to the central nervous system.

The morphological basis of feedback is the receptors located in the effector and the afferent neurons associated with them. Thanks to feedback afferent connections, fine regulation of the effector’s work and an adequate response of the body to environmental changes are carried out.

Meninges

The central nervous system (spinal cord and brain) has three connective tissue membranes: hard, arachnoid and soft. The outermost of these is the dura mater (it fuses with the periosteum lining the surface of the skull). The arachnoid membrane lies under the dura mater. It is pressed tightly against the hard surface and there is no free space between them.

Directly adjacent to the surface of the brain is the pia mater, which contains many blood vessels that supply the brain. Between the arachnoid and soft membranes there is a space filled with liquid - cerebrospinal fluid. The composition of cerebrospinal fluid is close to blood plasma and intercellular fluid and plays an anti-shock role. In addition, the cerebrospinal fluid contains lymphocytes that provide protection against foreign substances. It is also involved in the metabolism between the cells of the spinal cord, brain and blood (Fig. 11 A).


1 - dentate ligament, the process of which passes through the arachnoid membrane located on the side, 1a - dentate ligament attached to the dura mater of the spinal cord, 2 - arachnoid membrane, 3 - posterior root passing in the canal formed by the soft and arachnoid membranes, For - posterior root passing through the hole in the dura mater of the spinal cord, 36 - dorsal branches of the spinal nerve passing through the arachnoid membrane, 4 - spinal nerve, 5 - spinal ganglion, 6 - dura mater of the spinal cord, 6a - dura mater turned to the side , 7 - pia mater of the spinal cord with the posterior spinal artery.

Rice. 11A. Spinal cord membranes

Brain cavities

Inside the spinal cord is the spinal canal, which, passing into the brain, expands in the medulla oblongata and forms the fourth ventricle. At the level of the midbrain, the ventricle passes into a narrow canal - the aqueduct of Sylvius. In the diencephalon, the Sylvian aqueduct expands, forming the cavity of the third ventricle, which smoothly passes at the level of the cerebral hemispheres into the lateral ventricles (I and II). All of the listed cavities are also filled with cerebrospinal fluid (Fig. 11 B)

Figure 11B. Diagram of the ventricles of the brain and their relationship to the surface structures of the cerebral hemispheres.

a - cerebellum, b - occipital pole, c - parietal pole, d - frontal pole, e - temporal pole, f - medulla oblongata.

1 - lateral opening of the fourth ventricle (Lushka's foramen), 2 - lower horn of the lateral ventricle, 3 - aqueduct, 4 - recessusinfundibularis, 5 - recrssusopticus, 6 - interventricular foramen, 7 - anterior horn of the lateral ventricle, 8 - central part of the lateral ventricle, 9 - fusion of the visual tuberosities (massainter-melia), 10 - third ventricle, 11 - recessus pinealis, 12 - entrance to the lateral ventricle, 13 - posterior pro of the lateral ventricle, 14 - fourth ventricle.

Rice. 11. Meninges (A) and cavities of the brain (B)

SECTION II. STRUCTURE OF THE CENTRAL NERVOUS SYSTEM

Spinal cord

External structure of the spinal cord

The spinal cord is a flattened cord located in the spinal canal. Depending on the parameters of the human body, its length is 41-45 cm, average diameter is 0.48-0.84 cm, weight is about 28-32 g. In the center of the spinal cord there is a spinal canal filled with cerebrospinal fluid, and by the anterior and posterior longitudinal grooves it is divided into the right and left half.

In front, the spinal cord passes into the brain, and in the back it ends with the conus medullaris at the level of the 2nd vertebra of the lumbar spine. A connective tissue filum terminale (a continuation of the terminal membranes) departs from the conus medullaris, which attaches the spinal cord to the coccyx. The filum terminale is surrounded by nerve fibers (cauda equina) (Fig. 12).

There are two thickenings on the spinal cord - cervical and lumbar, from which nerves arise that innervate, respectively, the skeletal muscles of the arms and legs.

The spinal cord is divided into cervical, thoracic, lumbar and sacral sections, each of which is divided into segments: cervical - 8 segments, thoracic - 12, lumbar - 5, sacral 5-6 and 1 - coccygeal. Thus, the total number of segments is 31 (Fig. 13). Each segment of the spinal cord has paired spinal roots - anterior and posterior. Through the dorsal roots, information from receptors in the skin, muscles, tendons, ligaments, and joints enters the spinal cord, which is why the dorsal roots are called sensory (sensitive). Transection of the dorsal roots turns off tactile sensitivity, but does not lead to loss of movement.
Rice. 12. Spinal cord.

a - front view (its ventral surface);

b - rear view (its dorsal surface).

The dura and arachnoid membranes are cut. The choroid is removed. Roman numerals indicate the order of cervical (c), thoracic (th), lumbar (t)

and sacral(s) spinal nerves.

1 - cervical thickening

2 - spinal ganglion

3 - hard shell

4 - lumbar thickening

5 - conus medullaris

6 - terminal thread

Rice. 13. Spinal cord and spinal nerves (31 pairs).

Along the anterior roots of the spinal cord, nerve impulses travel to the skeletal muscles of the body (except for the muscles of the head), causing them to contract, which is why the anterior roots are called motor or motor. After cutting the anterior roots on one side, there is a complete shutdown of motor reactions, while sensitivity to touch or pressure remains.

The anterior and posterior roots of each side of the spinal cord unite to form the spinal nerves. Spinal nerves are called segmental; their number corresponds to the number of segments and is 31 pairs (Fig. 14)


The distribution of spinal nerve zones by segment was established by determining the size and boundaries of the skin areas (dermatomes) innervated by each nerve. Dermatomes are located on the surface of the body according to a segmental principle. Cervical dermatomes include the back surface of the head, neck, shoulders and anterior surface of the forearms. Thoracic sensory neurons innervate the remaining surface of the forearm, chest, and most of the abdomen. Sensory fibers from the lumbar, sacral, and coccygeal segments extend to the rest of the abdomen and legs.

Rice. 14. Scheme of dermatomes. Innervation of the body surface by 31 pairs of spinal nerves (C - cervical, T - thoracic, L - lumbar, S - sacral).

Internal structure of the spinal cord

The spinal cord is built according to the nuclear type. There is gray matter around the spinal canal, and white matter at the periphery. Gray matter is formed by neuron somas and branching dendrites that do not have myelin sheaths. White matter is a collection of nerve fibers covered with myelin sheaths.

In the gray matter, anterior and posterior horns are distinguished, between which lies the interstitial zone. There are lateral horns in the thoracic and lumbar regions of the spinal cord.

The gray matter of the spinal cord is formed by two groups of neurons: efferent and intercalary. The bulk of the gray matter consists of interneurons (up to 97%) and only 3% are efferent neurons or motor neurons. Motor neurons are located in the anterior horns of the spinal cord. Among them, a- and g-motoneurons are distinguished: a-motoneurons innervate skeletal muscle fibers and are large cells with relatively long dendrites; g-motoneurons are small cells and innervate muscle receptors, increasing their excitability.

Interneurons are involved in information processing, ensuring coordinated operation of sensory and motor neurons, and also connect the right and left halves of the spinal cord and its various segments (Fig. 15 A, B, C)

Rice. 15A. 1 - white matter of the brain; 2 - spinal canal; 3 - posterior longitudinal groove; 4 - posterior root of the spinal nerve; 5 – spinal node; 6 - spinal nerve; 7 - gray matter of the brain; 8 - anterior root of the spinal nerve; 9 - anterior longitudinal groove

Rice. 15B. Gray matter nuclei in the thoracic region

1,2,3 - sensitive nuclei of the posterior horn; 4, 5 - intercalary nuclei of the lateral horn; 6,7, 8,9,10 - motor nuclei of the anterior horn; I, II, III - anterior, lateral and posterior cords of white matter.


The contacts between sensory, intercalary and motor neurons in the gray matter of the spinal cord are depicted.

Rice. 15. Cross section of the spinal cord

Spinal cord pathways

The white matter of the spinal cord surrounds the gray matter and forms the columns of the spinal cord. There are front, rear and side pillars. The columns are tracts of the spinal cord formed by long axons of neurons running up towards the brain (ascending tracts) or down from the brain to lower segments of the spinal cord (descending tracts).

The ascending tracts of the spinal cord transmit information from receptors in muscles, tendons, ligaments, joints and skin to the brain. The ascending pathways are also conductors of temperature and pain sensitivity. All ascending pathways intersect at the level of the spinal cord (or brain). Thus, the left half of the brain (the cerebral cortex and the cerebellum) receives information from the receptors on the right half of the body and vice versa.

Main ascending paths: from the mechanoreceptors of the skin and the receptors of the musculoskeletal system - these are muscles, tendons, ligaments, joints - the Gaulle and Burdach bundles or, respectively, the tender and wedge-shaped bundles are represented by the posterior columns of the spinal cord.

From these same receptors, information enters the cerebellum along two pathways represented by lateral columns, which are called the anterior and posterior spinocerebellar tracts. In addition, two more pathways pass through the lateral columns - these are the lateral and anterior spinothalamic tracts, which transmit information from temperature and pain sensitivity receptors.

The posterior columns provide faster transmission of information about the localization of stimuli than the lateral and anterior spinothalamic tracts (Fig. 16 A).

1 - Gaulle's bundle, 2 - Burdach's bundle, 3 - dorsal spinocerebellar tract, 4 - ventral spinocerebellar tract. Neurons of groups I-IV.

Rice. 16A. Ascending tracts of the spinal cord

Descending Paths, passing through the anterior and lateral columns of the spinal cord, are motor, as they affect the functional state of the skeletal muscles of the body. The pyramidal tract begins mainly in the motor cortex of the hemispheres and passes to the medulla oblongata, where most of the fibers cross and pass to the opposite side. After this, the pyramidal tract is divided into lateral and anterior bundles: the anterior and lateral pyramidal tracts, respectively. Most pyramidal tract fibers terminate on interneurons, and about 20% form synapses on motor neurons. The pyramidal influence is exciting. Reticulospinal path, rubrospinal way and vestibulospinal the pathway (extrapyramidal system) begins respectively from the nuclei of the reticular formation, the brain stem, the red nuclei of the midbrain and the vestibular nuclei of the medulla oblongata. These pathways run in the lateral columns of the spinal cord and are involved in coordinating movements and ensuring muscle tone. Extrapyramidal tracts, like pyramidal tracts, are crossed (Fig. 16 B).

The main descending spinal tracts of the pyramidal (lateral and anterior corticospinal tracts) and extra pyramidal (rubrospinal, reticulospinal and vestibulospinal tracts) systems.

Rice. 16 B. Diagram of pathways

Thus, the spinal cord performs two important functions: reflex and conduction. The reflex function is carried out due to the motor centers of the spinal cord: motor neurons of the anterior horns ensure the functioning of the skeletal muscles of the body. At the same time, maintaining muscle tone, coordinating the work of the flexor-extensor muscles that underlie the movements, and maintaining the constancy of the posture of the body and its parts are maintained (Fig. 17 A, B, C). Motor neurons located in the lateral horns of the thoracic segments of the spinal cord provide respiratory movements (inhalation-exhalation, regulating the work of the intercostal muscles). Motor neurons of the lateral horns of the lumbar and sacral segments represent the motor centers of smooth muscles that are part of the internal organs. These are the centers of urination, defecation, and the functioning of the genital organs.

Rice. 17A. The arc of the tendon reflex.

Rice. 17B. Arcs of the flexion and cross-extensor reflex.


Rice. 17V. Elementary diagram of an unconditioned reflex.

Nerve impulses arising from stimulation of the receptor (p) along afferent fibers (afferent nerve, only one such fiber is shown) go to the spinal cord (1), where through the interneuron they are transmitted to efferent fibers (efferent nerve), along which they reach effector. The dotted lines represent the spread of excitation from the lower parts of the central nervous system to its higher parts (2, 3,4) up to the cerebral cortex (5) inclusive. The resulting change in the state of the higher parts of the brain in turn affects (see arrows) the efferent neuron, influencing the final result of the reflex response.

Rice. 17. Reflex function of the spinal cord

The conduction function is performed by the spinal tracts (Fig. 18 A, B, C, D, E).


Rice. 18A. Rear pillars. This circuit, formed by three neurons, transmits information from pressure and touch receptors to the somatosensory cortex.


Rice. 18B. Lateral spinothalamic tract. Along this path, information from temperature and pain receptors reaches large areas of the coronary brain.


Rice. 18V. Anterior spinothalamic tract. Along this pathway, information from pressure and touch receptors, as well as pain and temperature receptors, enters the somatosensory cortex.


Rice. 18G. Extrapyramidal system. Rubrospinal and reticulospinal tracts, which are part of the multineural extrapyramidal tract running from the cerebral cortex to the spinal cord.


Rice. 18D. Pyramidal or corticospinal tract

Rice. 18. Conductive function of the spinal cord

SECTION III. BRAIN.

General diagram of the structure of the brain (Fig. 19)

Brain

Figure 19A. Brain

1. Frontal cortex (cognitive area)

2. Motor cortex

3. Visual cortex

4. Cerebellum 5. Auditory cortex


Figure 19B. Side view

Figure 19B. The main formations of the medal surface of the brain in a midsagittal section.

Figure 19G. Lower surface of the brain

Rice. 19. Structure of the brain

hindbrain

The hindbrain, including the medulla oblongata and the pons, is a phylogenetically ancient region of the central nervous system, retaining the features of a segmental structure. The hindbrain contains nuclei and ascending and descending pathways. Afferent fibers from vestibular and auditory receptors, from receptors in the skin and muscles of the head, from receptors in internal organs, as well as from higher structures of the brain enter the hindbrain along the pathways. The hindbrain contains the nuclei of the V-XII pairs of cranial nerves, some of which innervate the facial and oculomotor muscles.

Medulla oblongata

The medulla oblongata is located between the spinal cord, the pons and the cerebellum (Fig. 20). On the ventral surface of the medulla oblongata, the anterior median groove runs along the midline; on its sides there are two cords - pyramids; olives lie on the side of the pyramids (Fig. 20 A-B).

Rice. 20A. 1 - cerebellum 2 - cerebellar peduncles 3 - pons 4 - medulla oblongata


Rice. 20V. 1 - bridge 2 - pyramid 3 - olive 4 - anterior medial fissure 5 - anterior lateral groove 6 - cross of the anterior cord 7 - anterior cord 8 - lateral cord

Rice. 20. Medulla oblongata

On the posterior side of the medulla oblongata there is a posterior medial groove. On its sides lie the posterior cords, which go to the cerebellum as part of the hind legs.

Gray matter of the medulla oblongata

The medulla oblongata contains the nuclei of four pairs of cranial nerves. These include the nuclei of the glossopharyngeal, vagus, accessory and hypoglossal nerves. In addition, the tender, wedge-shaped nuclei and cochlear nuclei of the auditory system, the nuclei of the inferior olives and the nuclei of the reticular formation (giant cell, parvocellular and lateral), as well as the respiratory nuclei are distinguished.

The nuclei of the hypoglossal (XII pair) and accessory (XI pair) nerves are motor, innervating the muscles of the tongue and the muscles that move the head. The nuclei of the vagus (X pair) and glossopharyngeal (IX pair) nerves are mixed; they innervate the muscles of the pharynx, larynx, and thyroid gland, and regulate swallowing and chewing. These nerves consist of afferent fibers coming from the receptors of the tongue, larynx, trachea and from the receptors of the internal organs of the chest and abdominal cavity. Efferent nerve fibers innervate the intestines, heart and blood vessels.

The nuclei of the reticular formation not only activate the cerebral cortex, maintaining consciousness, but also form the respiratory center, which ensures respiratory movements.

Thus, some of the nuclei of the medulla oblongata regulate vital functions (these are the nuclei of the reticular formation and the nuclei of the cranial nerves). The other part of the nuclei is part of the ascending and descending pathways (grass and cuneate nuclei, cochlear nuclei of the auditory system) (Fig. 21).
1-thin core;

2 - wedge-shaped nucleus;

3 - the end of the fibers of the posterior cords of the spinal cord;

4 - internal arcuate fibers - the second neuron of the propria pathway of the cortical direction;

5 - the intersection of loops is located in the inter-olive loop layer;

6 - medial loop - continuation of the internal arcuate voles

7 - seam, formed by the intersection of loops;

8 - olive core - intermediate core of balance;

9 - pyramidal paths;

10 - central channel.

Rice. 21. Internal structure of the medulla oblongata

White matter of the medulla oblongata

The white matter of the medulla oblongata is formed by long and short nerve fibers

Long nerve fibers are part of the descending and ascending pathways. Short nerve fibers ensure coordinated functioning of the right and left halves of the medulla oblongata.

Pyramids medulla oblongata - part descending pyramidal tract, going to the spinal cord and ending at interneurons and motor neurons. In addition, the rubrospinal tract passes through the medulla oblongata. The descending vestibulospinal and reticulospinal tracts originate in the medulla oblongata, respectively, from the vestibular and reticular nuclei.

The ascending spinocerebellar tracts pass through olives medulla oblongata and through the cerebral peduncles and transmit information from the receptors of the musculoskeletal system to the cerebellum.

Tender And wedge-shaped nuclei The medulla oblongata is part of the spinal cord pathways of the same name, running through the visual thalamus of the diencephalon to the somatosensory cortex.

Through cochlear auditory nuclei and through vestibular nuclei ascending sensory pathways from auditory and vestibular receptors. In the projection zone of the temporal cortex.

Thus, the medulla oblongata regulates the activity of many vital functions of the body. Therefore, the slightest damage to the medulla oblongata (trauma, swelling, hemorrhage, tumors) usually leads to death.

Pons

The pons is a thick ridge that borders the medulla oblongata and the cerebellar peduncles. The ascending and descending tracts of the medulla oblongata pass through the bridge without interruption. At the junction of the pons and the medulla oblongata, the vestibulocochlear nerve (VIII pair) emerges. The vestibulocochlear nerve is sensitive and transmits information from the auditory and vestibular receptors of the inner ear. In addition, the pons contains mixed nerves, the nuclei of the trigeminal nerve (V pair), abducens nerve (VI pair), and facial nerve (VII pair). These nerves innervate the facial muscles, scalp, tongue, and lateral rectus muscles of the eye.

On a cross section, the bridge consists of a ventral and dorsal part - between them the border is the trapezoidal body, the fibers of which are attributed to the auditory tract. In the region of the trapezius body there is a medial parabranchial nucleus, which is connected with the dentate nucleus of the cerebellum. The pontine nucleus proper communicates the cerebellum with the cerebral cortex. In the dorsal part of the bridge lie the nuclei of the reticular formation and the ascending and descending pathways of the medulla oblongata continue.

The bridge performs complex and varied functions aimed at maintaining posture and maintaining body balance in space when changing speed.

Vestibular reflexes are very important, the reflex arcs of which pass through the bridge. They provide tone to the neck muscles, stimulation of the autonomic centers, breathing, heart rate, and activity of the gastrovascular tract.

The nuclei of the trigeminal, glossopharyngeal, vagus and pontine nerves are associated with the grasping, chewing and swallowing of food.

Neurons of the reticular formation of the bridge play a special role in activating the cerebral cortex and limiting the sensory influx of nerve impulses during sleep (Fig. 22, 23)

Rice. 22. Medulla oblongata and pons.

A. Top view (dorsal side).

B. Side view.

B. View from below (from the ventral side).

1 - uvula, 2 - anterior medullary velum, 3 - median eminence, 4 - superior fossa, 5 - superior cerebellar peduncle, 6 - middle cerebellar peduncle, 7 - facial tubercle, 8 - inferior cerebellar peduncle, 9 - auditory tubercle, 10 - brain stripes, 11 - band of the fourth ventricle, 12 - triangle of the hypoglossal nerve, 13 - triangle of the vagus nerve, 14 - areapos-terma, 15 - obex, 16 - tubercle of the sphenoid nucleus, 17 - tubercle of the tender nucleus, 18 - lateral cord, 19 - posterior lateral sulcus, 19 a - anterior lateral sulcus, 20 - sphenoid cord, 21 - posterior intermediate sulcus, 22 - tender cord, 23 - posterior median sulcus, 23 a - pons - base), 23 b - pyramid of the medulla oblongata, 23 c -olive, 23 g - decussation of pyramids, 24 - cerebral peduncle, 25 - lower tubercle, 25 a - handle of the lower tubercle, 256 - superior tubercle

1 - trapezoid body 2 - nucleus of the superior olive 3 - dorsal contains the nuclei of VIII, VII, VI, V pairs of cranial nerves 4 - medal part of the pons 5 - ventral part of the pons contains its own nuclei and pons 7 - transverse nuclei of the pons 8 - pyramidal tracts 9 - middle cerebellar peduncle.

Rice. 23. Diagram of the internal structure of the bridge in a frontal section

Cerebellum

The cerebellum is a part of the brain located behind the cerebral hemispheres above the medulla oblongata and the pons.

Anatomically, the cerebellum is divided into a middle part - the vermis, and two hemispheres. With the help of three pairs of legs (lower, middle and superior), the cerebellum is connected to the brain stem. The lower legs connect the cerebellum with the medulla oblongata and spinal cord, the middle ones with the pons, and the upper ones with the mesencephalon and diencephalon (Fig. 24).


1 - vermis 2 - central lobule 3 - uvula vermis 4 - anterior velum of the cerebellum 5 - superior hemisphere 6 - anterior cerebellar peduncle 8 - peduncle of the cerebellum 8 - peduncle of the flocculus 9 - flocculus 10 - superior semilunar lobule 11 - inferior semilunar lobule 12 - inferior hemisphere 13 - digastric lobule 14 - cerebellar lobule 15 - cerebellar tonsil 16 - vermis pyramid 17 - wing of the central lobule 18 - node 19 - apex 20 - groove 21 - vermis hub 22 - vermis tubercle 23 - quadrangular lobule.

Rice. 24. Internal structure of the cerebellum

The cerebellum is built according to the nuclear type - the surface of the hemispheres is represented by gray matter, which makes up the new cortex. The cortex forms convolutions that are separated from each other by grooves. Under the cerebellar cortex there is white matter, in the thickness of which the paired cerebellar nuclei are distinguished (Fig. 25). These include tent cores, spherical core, cork core, jagged core. The tent nuclei are associated with the vestibular apparatus, the spherical and cortical nuclei are associated with the movement of the torso, and the dentate nucleus is associated with the movement of the limbs.

1- anterior cerebellar peduncles; 2 - tent cores; 3 - dentate core; 4 - corky core; 5 - white substance; 6 - cerebellar hemispheres; 7 – worm; 8 globular nucleus

Rice. 25. Cerebellar nuclei

The cerebellar cortex is of the same type and consists of three layers: molecular, ganglion and granular, in which there are 5 types of cells: Purkinje cells, basket, stellate, granular and Golgi cells (Fig. 26). In the superficial, molecular layer, there are dendritic branches of Purkinje cells, which are one of the most complex neurons in the brain. Dendritic processes are abundantly covered with spines, indicating a large number of synapses. In addition to Purkinje cells, this layer contains many axons of parallel nerve fibers (T-shaped branching axons of granular cells). In the lower part of the molecular layer there are bodies of basket cells, the axons of which form synaptic contacts in the region of the axon hillocks of Purkinje cells. The molecular layer also contains stellate cells.


A. Purkinje cell. B. Granule cells.

B. Golgi cell.

Rice. 26. Types of cerebellar neurons.

Below the molecular layer is the ganglion layer, which contains the bodies of Purkinje cells.

The third layer - granular - is represented by the bodies of interneurons (granule cells or granular cells). In the granular layer there are also Golgi cells, the axons of which rise into the molecular layer.

Only two types of afferent fibers enter the cerebellar cortex: climbing and mossy, which carry nerve impulses to the cerebellum. Each climbing fiber has contact with one Purkinje cell. The branches of the mossy fiber form contacts mainly with granule neurons, but do not contact Purkinje cells. Mossy fiber synapses are excitatory (Fig. 27).


Excitatory impulses arrive to the cortex and nuclei of the cerebellum via both climbing and mossy fibers. From the cerebellum, signals come only from Purkinje cells (P), which inhibit the activity of neurons in nuclei 1 of the cerebellum (P). The intrinsic neurons of the cerebellar cortex include excitatory granule cells (3) and inhibitory basket neurons (K), Golgi neurons (G) and stellate neurons (Sv). The arrows indicate the direction of movement of nerve impulses. There are both exciting (+) and; inhibitory (-) synapses.

Rice. 27. Neural circuit of the cerebellum.

Thus, the cerebellar cortex includes two types of afferent fibers: climbing and mossy. These fibers transmit information from tactile receptors and receptors of the musculoskeletal system, as well as from all brain structures that regulate the motor function of the body.

The efferent influence of the cerebellum is carried out through the axons of Purkinje cells, which are inhibitory. The axons of Purkinje cells exert their influence either directly on motor neurons of the spinal cord, or indirectly through neurons of the cerebellar nuclei or other motor centers.

In humans, due to upright posture and work activity, the cerebellum and its hemispheres reach their greatest development and size.

When the cerebellum is damaged, imbalances and muscle tone are observed. The nature of the violations depends on the location of the damage. Thus, when the tent cores are damaged, the balance of the body is disrupted. This manifests itself in a staggering gait. If the worm, cork and spherical nuclei are damaged, the work of the muscles of the neck and torso is disrupted. The patient has difficulty eating. If the hemispheres and dentate nucleus are damaged, the work of the muscles of the limbs (tremor) is affected, and his professional activity becomes difficult.

In addition, in all patients with cerebellar damage due to impaired coordination of movements and tremor (shaking), fatigue quickly occurs.

Midbrain

The midbrain, like the medulla oblongata and the pons, belongs to the stem structures (Fig. 28).


1 - commissure of leashes

2 - leash

3 - pineal gland

4 - superior colliculus of the midbrain

5 - medial geniculate body

6 - lateral geniculate body

7 - inferior colliculus of the midbrain

8 - superior cerebellar peduncles

9 - middle cerebellar peduncles

10 - inferior cerebellar peduncles

11- medulla oblongata

Rice. 28. Hindbrain

The midbrain consists of two parts: the roof of the brain and the cerebral peduncles. The roof of the midbrain is represented by the quadrigemina, in which the superior and inferior colliculi are distinguished. In the thickness of the cerebral peduncles, paired clusters of nuclei are distinguished, called the substantia nigra and the red nucleus. Through the midbrain there are ascending pathways to the diencephalon and cerebellum and descending pathways from the cerebral cortex, subcortical nuclei and diencephalon to the nuclei of the medulla oblongata and spinal cord.

In the lower colliculi of the quadrigemina there are neurons that receive afferent signals from auditory receptors. Therefore, the lower tubercles of the quadrigeminal are called the primary auditory center. The reflex arc of the indicative auditory reflex passes through the primary auditory center, which manifests itself in turning the head towards the acoustic signal.

The superior colliculus is the primary visual center. The neurons of the primary visual center receive afferent impulses from photoreceptors. The superior colliculus provides an indicative visual reflex - turning the head towards the visual stimulus.

The nuclei of the lateral and oculomotor nerves take part in the implementation of orientation reflexes, which innervate the muscles of the eyeball, ensuring its movement.

The red nucleus contains neurons of different sizes. The descending rubrospinal tract begins from the large neurons of the red nucleus, which affects motor neurons and finely regulates muscle tone.

The neurons of the substantia nigra contain the pigment melanin and give this nucleus its dark color. The substantia nigra, in turn, sends signals to neurons in the reticular nuclei of the brain stem and subcortical nuclei.

The substantia nigra is involved in complex coordination of movements. It contains dopaminergic neurons, i.e. releasing dopamine as a mediator. One part of these neurons regulates emotional behavior, the other plays an important role in the control of complex motor acts. Damage to the substantia nigra, leading to degeneration of dopaminergic fibers, causes the inability to begin performing voluntary movements of the head and arms when the patient sits quietly (Parkinson's disease) (Fig. 29 A, B).

Rice. 29A. 1 - colliculus 2 - aqueduct of the cerebellum 3 - central gray matter 4 - substantia nigra 5 - medial sulcus of the cerebral peduncle

Rice. 29B. Diagram of the internal structure of the midbrain at the level of the inferior colliculi (frontal section)

1 - nucleus of the inferior colliculus, 2 - motor tract of the extrapyramidal system, 3 - dorsal decussation of the tegmentum, 4 - red nucleus, 5 - red nucleus - spinal tract, 6 - ventral decussation of the tegmentum, 7 - medial lemniscus, 8 - lateral lemniscus, 9 - reticular formation, 10 - medial longitudinal fasciculus, 11 - nucleus of the midbrain tract of the trigeminal nerve, 12 - nucleus of the lateral nerve, I-V - descending motor tracts of the cerebral peduncle

Rice. 29. Diagram of the internal structure of the midbrain

Diencephalon

The diencephalon forms the walls of the third ventricle. Its main structures are the visual tuberosities (thalamus) and the subtuberculous region (hypothalamus), as well as the supratubercular region (epithalamus) (Fig. 30 A, B).

Rice. 30 A. 1 - thalamus (visual thalamus) - the subcortical center of all types of sensitivity, the “sensory” of the brain; 2 - epithalamus (supratubercular region); 3 - metathalamus (foreign region).

Rice. 30 B. Circuits of the visual brain ( thalamencephalon ): a - top view b - rear and bottom view.

Thalamus (visual thalamus) 1 - anterior burf of the visual thalamus, 2 - cushion 3 - intertubercular fusion 4 - medullary strip of the visual thalamus

Epithalamus (supratubercular region) 5 - triangle of the leash, 6 - leash, 7 - commissure of the leash, 8 - pineal body (epiphysis)

Metathalamus (external region) 9 - lateral geniculate body, 10 - medial geniculate body, 11 - III ventricle, 12 - roof of the midbrain

Rice. 30. Visual Brain

Deep in the brain tissue of the diencephalon, the nuclei of the external and internal geniculate bodies are located. The outer border is formed by the white matter that separates the diencephalon from the telencephalon.

Thalamus (visual thalamus)

The neurons of the thalamus form 40 nuclei. Topographically, the nuclei of the thalamus are divided into anterior, median and posterior. Functionally, these nuclei can be divided into two groups: specific and nonspecific.

Specific nuclei are part of specific pathways. These are ascending pathways that transmit information from sensory organ receptors to the projection zones of the cerebral cortex.

The most important of the specific nuclei are the lateral geniculate body, which is involved in transmitting signals from photoreceptors, and the medial geniculate body, which transmits signals from auditory receptors.

The nonspecific ribs of the thalamus are classified as the reticular formation. They act as integrative centers and have a predominantly activating ascending effect on the cerebral cortex (Fig. 31 A, B)


1 - anterior group (olfactory); 2 - posterior group (visual); 3 - lateral group (general sensitivity); 4 - medial group (extrapyramidal system; 5 - central group (reticular formation).

Rice. 31B. Frontal section of the brain at the level of the middle of the thalamus. 1a - anterior nucleus of the visual thalamus. 16 - medial nucleus of the visual thalamus, 1c - lateral nucleus of the visual thalamus, 2 - lateral ventricle, 3 - fornix, 4 - caudate nucleus, 5 - internal capsule, 6 - external capsule, 7 - external capsule (capsula extrema), 8 - ventral nucleus thalamus optica, 9 - subthalamic nucleus, 10 - third ventricle, 11 - cerebral peduncle. 12 - bridge, 13 - interpeduncular fossa, 14 - hippocampal peduncle, 15 - inferior horn of the lateral ventricle. 16 - black substance, 17 - insula. 18 - pale ball, 19 - shell, 20 - Trout N fields; and b. 21 - interthalamic fusion, 22 - corpus callosum, 23 - tail of the caudate nucleus.

Figure 31. Diagram of groups of thalamus nuclei


Activation of neurons in the nonspecific nuclei of the thalamus is especially effective in causing pain signals (the thalamus is the highest center of pain sensitivity).

Damage to the nonspecific nuclei of the thalamus also leads to impairment of consciousness: loss of active communication between the body and the environment.

Subthalamus (hypothalamus)

The hypothalamus is formed by a group of nuclei located at the base of the brain. The nuclei of the hypothalamus are the subcortical centers of the autonomic nervous system of all vital functions of the body.

Topographically, the hypothalamus is divided into the preoptic area, the areas of the anterior, middle and posterior hypothalamus. All nuclei of the hypothalamus are paired (Fig. 32 A-D).

1 - aqueduct 2 - red nucleus 3 - tegmentum 4 - substantia nigra 5 - cerebral peduncle 6 - mastoid bodies 7 - anterior perforated substance 8 - oblique triangle 9 - infundibulum 10 - optic chiasm 11. optic nerve 12 - gray tubercle 13 - posterior perforated substance 14 - external geniculate body 15 - medial geniculate body 16 - cushion 17 - optic tract

Rice. 32A. Metathalamus and hypothalamus


a - bottom view; b - mid sagittal section.

Visual part (parsoptica): 1 - terminal plate; 2 - visual chiasm; 3 - visual tract; 4 - gray tubercle; 5 - funnel; 6 - pituitary gland;

Olfactory part: 7 - mamillary bodies - subcortical olfactory centers; 8 - the subcutaneous region in the narrow sense of the word is a continuation of the cerebral peduncles, contains the substantia nigra, the red nucleus and the Lewis body, which is a link in the extrapyramidal system and the vegetative center; 9 - subtubercular Monroe's groove; 10 - sella turcica, in the fossa of which the pituitary gland is located.

Rice. 32B. Subcutaneous region (hypothalamus)

Rice. 32V. Main nuclei of the hypothalamus


1 - nucleus supraopticus; 2 - nucleus preopticus; 3 - nucliusparaventricularis; 4 - nucleus in fundibularus; 5 - nucleuscorporismamillaris; 6 - visual chiasm; 7 - pituitary gland; 8 - gray tubercle; 9 - mastoid body; 10 bridge.

Rice. 32G. Scheme of the neurosecretory nuclei of the subthalamic region (Hypothalamus)

The preoptic area includes the periventricular, medial and lateral preoptic nuclei.

The anterior hypothalamus group includes the supraoptic, suprachiasmatic and paraventricular nuclei.

The middle hypothalamus makes up the ventromedial and dorsomedial nuclei.

In the posterior hypothalamus, the posterior hypothalamic, perifornical and mamillary nuclei are distinguished.

The connections of the hypothalamus are extensive and complex. Afferent signals to the hypothalamus come from the cerebral cortex, subcortical nuclei and thalamus. The main efferent pathways reach the midbrain, thalamus and subcortical nuclei.

The hypothalamus is the highest center for the regulation of the cardiovascular system, water-salt, protein, fat, and carbohydrate metabolism. This area of ​​the brain contains centers associated with the regulation of eating behavior. An important role of the hypothalamus is regulation. Electrical stimulation of the posterior nuclei of the hypothalamus leads to hyperthermia, as a result of increased metabolism.

The hypothalamus also takes part in maintaining the sleep-wake biorhythm.

The nuclei of the anterior hypothalamus are connected to the pituitary gland and transport biologically active substances that are produced by the neurons of these nuclei. Neurons of the preoptic nucleus produce releasing factors (statins and liberins) that control the synthesis and release of pituitary hormones.

Neurons of the preoptic, supraoptic, paraventricular nuclei produce true hormones - vasopressin and oxytocin, which descend along the axons of neurons to the neurohypophysis, where they are stored until released into the blood.

Neurons of the anterior pituitary gland produce 4 types of hormones: 1) somatotropic hormone, which regulates growth; 2) gonadotropic hormone, which promotes the growth of germ cells, the corpus luteum, and enhances milk production; 3) thyroid-stimulating hormone – stimulates the function of the thyroid gland; 4) adrenocorticotropic hormone - enhances the synthesis of hormones of the adrenal cortex.

The intermediate lobe of the pituitary gland secretes the hormone intermedin, which affects skin pigmentation.

The posterior lobe of the pituitary gland secretes two hormones - vasopressin, which affects the smooth muscles of the arterioles, and oxytocin, which acts on the smooth muscles of the uterus and stimulates the secretion of milk.

The hypothalamus also plays an important role in emotional and sexual behavior.

The epithalamus (pineal gland) includes the pineal gland. The pineal gland hormone, melatonin, inhibits the formation of gonadotropic hormones in the pituitary gland, and this in turn delays sexual development.

Forebrain

The forebrain consists of three anatomically separate parts - the cerebral cortex, white matter and subcortical nuclei.

In accordance with the phylogeny of the cerebral cortex, the ancient cortex (archicortex), old cortex (paleocortex) and new cortex (neocortex) are distinguished. The ancient cortex includes the olfactory bulbs, which receive afferent fibers from the olfactory epithelium, the olfactory tracts - located on the lower surface of the frontal lobe, and the olfactory tubercles - secondary olfactory centers.

The old cortex includes the cingulate cortex, hippocampal cortex, and amygdala.

All other areas of the cortex are neocortex. The ancient and old cortex is called the olfactory brain (Fig. 33).

The olfactory brain, in addition to functions related to smell, provides reactions of alertness and attention, and takes part in the regulation of the autonomic functions of the body. This system also plays an important role in the implementation of instinctive forms of behavior (eating, sexual, defensive) and the formation of emotions.

a - bottom view; b - on a sagittal section of the brain

Peripheral department: 1 - bulbusolfactorius (olfactory bulb; 2 - tractusolfactories (olfactory path); 3 - trigonumolfactorium (olfactory triangle); 4 - substantiaperforateanterior (anterior perforated substance).

Central section - convolutions of the brain: 5 - vaulted gyrus; 6 - hippocampus is located in the cavity of the lower horn of the lateral ventricle; 7 - continuation of the gray vestment of the corpus callosum; 8 - vault; 9 - transparent septum - conductive pathways of the olfactory brain.

Figure 33. Olfactory brain

Irritation of the structures of the old cortex affects the cardiovascular system and breathing, causes hypersexuality, and changes emotional behavior.

With electrical stimulation of the tonsil, effects associated with the activity of the digestive tract are observed: licking, chewing, swallowing, changes in intestinal motility. Irritation of the tonsil also affects the activity of internal organs - kidneys, bladder, uterus.

Thus, there is a connection between the structures of the old cortex and the autonomic nervous system, with processes aimed at maintaining the homeostasis of the internal environments of the body.

Finite brain

The telencephalon includes: the cerebral cortex, white matter and the subcortical nuclei located in its thickness.

The surface of the cerebral hemispheres is folded. Furrows - depressions divide it into lobes.

The central (Rolandian) sulcus separates the frontal lobe from the parietal lobe. The lateral (Sylvian) fissure separates the temporal lobe from the parietal and frontal lobes. The occipito-parietal sulcus forms the boundary between the parietal, occipital and temporal lobes (Fig. 34 A, B, Fig. 35)


1 - superior frontal gyrus; 2 - middle frontal gyrus; 3 - precentral gyrus; 4 - postcentral gyrus; 5 - inferior parietal gyrus; 6 - superior parietal gyrus; 7 - occipital gyrus; 8 - occipital groove; 9 - intraparietal sulcus; 10 - central groove; 11 - precentral gyrus; 12 - inferior frontal sulcus; 13 - superior frontal sulcus; 14 - vertical slot.

Rice. 34A. Brain from the dorsal surface

1 - olfactory groove; 2 - anterior perforated substance; 3 - hook; 4 - middle temporal sulcus; 5 - inferior temporal sulcus; 6 - seahorse groove; 7 - roundabout groove; 8 - calcarine groove; 9 - wedge; 10 - parahippocampal gyrus; 11 - occipitotemporal groove; 12 - inferior parietal gyrus; 13 - olfactory triangle; 14 - straight gyrus; 15 - olfactory tract; 16 - olfactory bulb; 17 - vertical slot.

Rice. 34B. Brain from the ventral surface


1 - central groove (Rolanda); 2 - lateral groove (Sylvian fissure); 3 - precentral sulcus; 4 - superior frontal sulcus; 5 - inferior frontal sulcus; 6 - ascending branch; 7 - anterior branch; 8 - postcentral groove; 9 - intraparietal sulcus; 10 - superior temporal sulcus; 11 - inferior temporal sulcus; 12 - transverse occipital groove; 13 - occipital groove.

Rice. 35. Grooves on the superolateral surface of the hemisphere (left side)

Thus, the grooves divide the hemispheres of the telencephalon into five lobes: the frontal, parietal, temporal, occipital and insular lobe, which is located under the temporal lobe (Fig. 36).

Rice. 36. Projection (marked with dots) and associative (light) zones of the cerebral cortex. Projection areas include the motor area (frontal lobe), somatosensory area (parietal lobe), visual area (occipital lobe), and auditory area (temporal lobe).


There are also grooves on the surface of each lobe.

There are three orders of furrows: primary, secondary and tertiary. The primary grooves are relatively stable and the deepest. These are the boundaries of large morphological parts of the brain. Secondary grooves extend from the primary ones, and tertiary ones from the secondary ones.

Between the grooves there are folds - convolutions, the shape of which is determined by the configuration of the grooves.

The frontal lobe is divided into the superior, middle and inferior frontal gyri. The temporal lobe contains the superior, middle and inferior temporal gyri. The anterior central gyrus (precentral) is located in front of the central sulcus. The posterior central gyrus (postcentral) is located behind the central sulcus.

In humans, there is great variability in the sulci and convolutions of the telencephalon. Despite this individual variability in the external structure of the hemispheres, this does not affect the structure of personality and consciousness.

Cytoarchitecture and myeloarchitecture of the neocortex

In accordance with the division of the hemispheres into five lobes, five main areas are distinguished - frontal, parietal, temporal, occipital and insular, which have differences in structure and perform different functions. However, the general plan of the structure of the new cortex is the same. The new crust is a layered structure (Fig. 37). I - molecular layer, formed mainly by nerve fibers running parallel to the surface. Among the parallel fibers there are a small number of granular cells. Under the molecular layer there is a second layer - the outer granular one. Layer III is the outer pyramidal layer, layer IV is the inner granular layer, layer V is the inner pyramidal layer and layer VI is multiform. The layers are named after the neurons. Accordingly, in layers II and IV, the neuron somas have a rounded shape (granular cells) (outer and internal granular layers), and in layers III and IV, the somas have a pyramidal shape (in the outer pyramidal there are small pyramids, and in the inner pyramidal layers there are large ones). pyramids or Betz cells). Layer VI is characterized by the presence of neurons of various shapes (fusiform, triangular, etc.).

The main afferent inputs to the cerebral cortex are nerve fibers coming from the thalamus. Cortical neurons that perceive afferent impulses traveling along these fibers are called sensory, and the area where sensory neurons are located is called projection zones of the cortex.

The main efferent outputs from the cortex are the axons of layer V pyramids. These are efferent, motor neurons involved in the regulation of motor functions. Most cortical neurons are intercortical, involved in information processing and providing intercortical connections.

Typical cortical neurons


Roman numerals indicate cell layers I - molecular layer; II - outer granular layer; III - outer pyramidal layer; IV - internal granular layer; V - inner primamide layer; VI-multiform layer.

a - afferent fibers; b - types of cells detected on preparations impregnated using the Goldbrzy method; c - cytoarchitecture revealed by Nissl staining. 1 - horizontal cells, 2 - Kees stripe, 3 - pyramidal cells, 4 - stellate cells, 5 - outer Bellarger stripe, 6 - inner Bellarger stripe, 7 - modified pyramidal cell.

Rice. 37. Cytoarchitecture (A) and myeloarchitecture (B) of the cerebral cortex.

While maintaining the general structural plan, it was found that different sections of the cortex (within one area) differ in the thickness of the layers. In some layers, several sublayers can be distinguished. In addition, there are differences in cellular composition (diversity of neurons, density and location). Taking into account all these differences, Brodman identified 52 areas, which he called cytoarchitectonic fields and designated in Arabic numerals from 1 to 52 (Fig. 38 A, B).

And the side view. B midsagittal; slice

Rice. 38. Field layout according to Boardman

Each cytoarchitectonic field differs not only in its cellular structure, but also in the location of the nerve fibers, which can run in both vertical and horizontal directions. The accumulation of nerve fibers within the cytoarchitectonic field is called myeloarchitectonics.

Currently, the “columnar principle” of organizing the projection zones of the cortex is becoming increasingly recognized.

According to this principle, each projection zone consists of a large number of vertically oriented columns, approximately 1 mm in diameter. Each column unites about 100 neurons, among which there are sensory, intercalary and efferent neurons, interconnected by synaptic connections. A single “cortical column” is involved in processing information from a limited number of receptors, i.e. performs a specific function.

Hemispheric fiber system

Both hemispheres have three types of fibers. Through projection fibers, excitation enters the cortex from receptors along specific pathways. Association fibers connect different areas of the same hemisphere. For example, the occipital region with the temporal region, the occipital region with the frontal region, the frontal region with the parietal region. Commissural fibers connect symmetrical areas of both hemispheres. Among the commissural fibers there are: anterior, posterior cerebral commissures and the corpus callosum (Fig. 39 A.B).

Rice. 39A. a - medial surface of the hemisphere;

b - upper-alteral surface of the hemisphere;

A - frontal pole;

B - occipital pole;

C - corpus callosum;

1 - arcuate fibers of the cerebrum connect neighboring gyri;

2 - belt - a bundle of the olfactory brain lies under the vaulted gyrus, extends from the region of the olfactory triangle to the hook;

3 - the lower longitudinal fasciculus connects the occipital and temporal regions;

4 - the superior longitudinal fasciculus connects the frontal, occipital, temporal lobes and the inferior parietal lobe;

5 - the uncinate fascicle is located at the anterior edge of the insula and connects the frontal pole with the temporal one.

Rice. 39B. Cerebral cortex in cross section. Both hemispheres are connected by bundles of white matter that form the corpus callosum (commissural fibers).

Rice. 39. Scheme of associative fibers

Reticular formation

The reticular formation (reticular substance of the brain) was described by anatomists at the end of the last century.

The reticular formation begins in the spinal cord, where it is represented by the gelatinous substance of the base of the hindbrain. Its main part is located in the central brain stem and diencephalon. It consists of neurons of various shapes and sizes, which have extensive branching processes running in different directions. Among the processes, short and long nerve fibers are distinguished. Short processes provide local connections, long ones form the ascending and descending paths of the reticular formation.

Clusters of neurons form nuclei that are located at different levels of the brain (dorsal, medulla, middle, intermediate). Most of the nuclei of the reticular formation do not have clear morphological boundaries and the neurons of these nuclei are united only by functional characteristics (respiratory, cardiovascular center, etc.). However, at the level of the medulla oblongata, nuclei with clearly defined boundaries are distinguished - the reticular giant cell, reticular parvocellular and lateral nuclei. The nuclei of the reticular formation of the pons are essentially a continuation of the nuclei of the reticular formation of the medulla oblongata. The largest of them are the caudal, medial and oral nuclei. The latter passes into the cell group of nuclei of the reticular formation of the midbrain and the reticular nucleus of the tegmentum of the brain. The cells of the reticular formation are the beginning of both ascending and descending pathways, giving numerous collaterals (endings) that form synapses on neurons of different nuclei of the central nervous system.

Fibers of reticular cells traveling to the spinal cord form the reticulospinal tract. Fibers of the ascending tracts, starting in the spinal cord, connect the reticular formation with the cerebellum, midbrain, diencephalon and cerebral cortex.

There are specific and nonspecific reticular formations. For example, some of the ascending pathways of the reticular formation receive collaterals from specific pathways (visual, auditory, etc.), along which afferent impulses are transmitted to the projection zones of the cortex.

Nonspecific ascending and descending pathways of the reticular formation affect the excitability of various parts of the brain, primarily the cerebral cortex and the spinal cord. These influences, according to their functional significance, can be both activating and inhibitory, therefore they are distinguished: 1) ascending activating influence, 2) ascending inhibitory influence, 3) descending activating influence, 4) descending inhibitory influence. Based on these factors, the reticular formation is considered as a regulating nonspecific brain system.

The most studied is the activating influence of the reticular formation on the cerebral cortex. Most of the ascending fibers of the reticular formation diffusely end in the cerebral cortex and maintain its tone and ensure attention. An example of inhibitory descending influences of the reticular formation is a decrease in the tone of human skeletal muscles during certain stages of sleep.

Neurons of the reticular formation are extremely sensitive to humoral substances. This is an indirect mechanism of influence of various humoral factors and the endocrine system on the higher parts of the brain. Consequently, the tonic effects of the reticular formation depend on the state of the whole organism (Fig. 40).

Rice. 40. The activating reticular system (ARS) is a nervous network through which sensory excitation is transmitted from the reticular formation of the brain stem to the nonspecific nuclei of the thalamus. Fibers from these nuclei regulate the level of activity of the cortex.


Subcortical nuclei

The subcortical nuclei are part of the telencephalon and are located inside the white matter of the cerebral hemispheres. These include the caudate body and putamen, collectively called the “striatum” (striatum) and the globus pallidus, consisting of the lentiform body, husk and tonsil. The subcortical nuclei and nuclei of the midbrain (red nucleus and substantia nigra) make up the system of basal ganglia (nuclei) (Fig. 41). The basal ganglia receives impulses from the motor cortex and cerebellum. In turn, signals from the basal ganglia are sent to the motor cortex, cerebellum and reticular formation, i.e. There are two neural loops: one connects the basal ganglia with the motor cortex, the other with the cerebellum.

Rice. 41. Basal ganglia system


The subcortical nuclei take part in the regulation of motor activity, regulating complex movements when walking, maintaining a posture, and when eating. They organize slow movements (stepping over obstacles, threading a needle, etc.).

There is evidence that the striatum is involved in the processes of memorizing motor programs, since irritation of this structure leads to impaired learning and memory. The striatum has an inhibitory effect on various manifestations of motor activity and on the emotional components of motor behavior, in particular on aggressive reactions.

The main transmitters of the basal ganglia are: dopamine (especially in the substantia nigra) and acetylcholine. Damage to the basal ganglia causes slow, writhing, involuntary movements accompanied by sharp muscle contractions. Involuntary jerky movements of the head and limbs. Parkinson's disease, the main symptoms of which are tremor (shaking) and muscle rigidity (a sharp increase in the tone of the extensor muscles). Due to rigidity, the patient can hardly begin to move. Constant tremor prevents small movements. Parkinson's disease occurs when the substantia nigra is damaged. Normally, the substantia nigra has an inhibitory effect on the caudate nucleus, putamen and globus pallidus. When it is destroyed, the inhibitory influences are eliminated, as a result of which the excitatory effect of the basal ganglia on the cerebral cortex and reticular formation increases, which causes the characteristic symptoms of the disease.

Limbic system

The limbic system is represented by sections of the new cortex (neocortex) and diencephalon located on the border. It unites complexes of structures of different phylogenetic ages, some of which are cortical, and some are nuclear.

The cortical structures of the limbic system include the hippocampal, parahippocampal and cingulate gyri (senile cortex). The ancient cortex is represented by the olfactory bulb and olfactory tubercles. The neocortex is part of the frontal, insular and temporal cortices.

The nuclear structures of the limbic system combine the amygdala and septal nuclei and anterior thalamic nuclei. Many anatomists consider the preoptic area of ​​the hypothalamus and the mammillary bodies to be part of the limbic system. The structures of the limbic system form 2-way connections and are connected to other parts of the brain.

The limbic system controls emotional behavior and regulates endogenous factors that provide motivation. Positive emotions are associated primarily with the excitation of adrenergic neurons, and negative emotions, as well as fear and anxiety, are associated with a lack of excitation of noradrenergic neurons.

The limbic system is involved in organizing orienting and exploratory behavior. Thus, “novelty” neurons were discovered in the hippocampus, changing their impulse activity when new stimuli appear. The hippocampus plays a significant role in maintaining the internal environment of the body and is involved in the processes of learning and memory.

Consequently, the limbic system organizes the processes of self-regulation of behavior, emotion, motivation and memory (Fig. 42).

Rice. 42. Limbic system


Autonomic nervous system

The autonomous (vegetative) nervous system provides regulation of internal organs, strengthening or weakening their activity, carries out an adaptive-trophic function, regulates the level of metabolism (metabolism) in organs and tissues (Fig. 43, 44).

1 - sympathetic trunk; 2 - cervicothoracic (stellate) node; 3 – middle cervical node; 4 - upper cervical node; 5 - internal carotid artery; 6 - celiac plexus; 7 - superior mesenteric plexus; 8 - inferior mesenteric plexus

Rice. 43. Sympathetic part of the autonomic nervous system,


III - oculomotor nerve; YII - facial nerve; IX - glossopharyngeal nerve; X - vagus nerve.

1 - ciliary node; 2 - pterygopalatine node; 3 - ear node; 4 - submandibular node; 5 - sublingual node; 6 - parasympathetic sacral nucleus; 7 - extramural pelvic node.

Rice. 44. Parasympathetic part of the autonomic nervous system.

The autonomic nervous system includes parts of both the central and peripheral nervous systems. Unlike the somatic nervous system, in the autonomic nervous system the efferent part consists of two neurons: preganglionic and postganglionic. Preganglionic neurons are located in the central nervous system. Postganglionic neurons are involved in the formation of autonomic ganglia.

The autonomic nervous system is divided into sympathetic and parasympathetic divisions.

In the sympathetic division, preganglionic neurons are located in the lateral horns of the spinal cord. The axons of these cells (preganglionic fibers) approach the sympathetic ganglia of the nervous system, located on both sides of the spine in the form of a sympathetic nerve chain.

Postganglionic neurons are located in the sympathetic ganglia. Their axons emerge as part of the spinal nerves and form synapses on the smooth muscles of internal organs, glands, vascular walls, skin and other organs.

In the parasympathetic nervous system, preganglionic neurons are located in the nuclei of the brainstem. The axons of preganglionic neurons are part of the oculomotor, facial, glossopharyngeal and vagus nerves. In addition, preganglionic neurons are also found in the sacral spinal cord. Their axons go to the rectum, bladder, and to the walls of the vessels that supply blood to the organs located in the pelvic area. Preganglionic fibers form synapses on postganglionic neurons of the parasympathetic ganglia located near or within the effector (in the latter case, the parasympathetic ganglion is called intramural).

All parts of the autonomic nervous system are subordinate to the higher parts of the central nervous system.

Functional antagonism of the sympathetic and parasympathetic nervous systems was noted, which is of great adaptive importance (see Table 1).


SECTION I V . DEVELOPMENT OF THE NERVOUS SYSTEM

The nervous system begins to develop in the 3rd week of intrauterine development from the ectoderm (outer germ layer).

On the dorsal (dorsal) side of the embryo, the ectoderm thickens. This forms the neural plate. The neural plate then bends deeper into the embryo and a neural groove is formed. The edges of the neural groove close together to form the neural tube. The long, hollow neural tube, which first lies on the surface of the ectoderm, is separated from it and plunges inward, under the ectoderm. The neural tube expands at the anterior end, from which the brain later forms. The rest of the neural tube is transformed into the brain (Fig. 45).

Rice. 45. Stages of embryogenesis of the nervous system in a transverse schematic section, a - medullary plate; b and c - medullary groove; d and e - brain tube. 1 - horny leaf (epidermis); 2 - ganglion cushion.

From cells migrating from the side walls of the neural tube, two neural crests are formed - nerve cords. Subsequently, spinal and autonomic ganglia and Schwann cells are formed from the nerve cords, which form the myelin sheaths of nerve fibers. In addition, neural crest cells participate in the formation of the pia mater and arachnoid membrane of the brain. In the inner part of the neural tube, increased cell division occurs. These cells differentiate into 2 types: neuroblasts (precursors of neurons) and spongioblasts (precursors of glial cells). Simultaneously with cell division, the head end of the neural tube is divided into three sections - the primary brain vesicles. Accordingly, they are called the forebrain (I bladder), middle (II bladder) and hindbrain (III bladder). In subsequent development, the brain is divided into the telencephalon (cerebral hemispheres) and diencephalon. The midbrain is preserved as a single whole, and the hindbrain is divided into two sections, including the cerebellum with the pons and the medulla oblongata. This is the 5-vesical stage of brain development (Fig. 46, 47).

a - five brain tracts: 1 - first vesicle (end brain); 2 - second bladder (diencephalon); 3 - third bladder (midbrain); 4- fourth vesicle (medulla oblongata); between the third and fourth bladder there is an isthmus; b - brain development (according to R. Sinelnikov).

Rice. 46. ​​Brain development (diagram)

A - formation of primary blisters (up to the 4th week of embryonic development). B - E - formation of secondary bubbles. B, C - end of the 4th week; G - sixth week; D - 8-9 weeks, ending with the formation of the main parts of the brain (E) - by 14 weeks.

3a - isthmus of the rhomboid brain; 7 end plate.

Stage A: 1, 2, 3 - primary brain vesicles

1 - forebrain,

2 - midbrain,

3 - hindbrain.

Stage B: the forebrain is divided into the hemispheres and basal ganglia (5) and diencephalon (6)

Stage B: The rhombencephalon (3a) is divided into the hindbrain, which includes the cerebellum (8), the pons (9) stage E and the medulla oblongata (10) stage E

Stage E: spinal cord is formed (4)

Rice. 47. The developing brain.

The formation of nerve vesicles is accompanied by the appearance of bends due to different rates of maturation of parts of the neural tube. By the 4th week of intrauterine development, the parietal and occipital curves are formed, and during the 5th week, the pontine curve is formed. By the time of birth, only the bend of the brain stem remains almost at a right angle in the area of ​​​​the junction of the midbrain and diencephalon (Fig. 48).

Lateral view illustrating curves in the midbrain (A), cervical (B), and pons (C).

1 - optic vesicle, 2 - forebrain, 3 - midbrain; 4 - hindbrain; 5 - auditory vesicle; 6 - spinal cord; 7 - diencephalon; 8 - telencephalon; 9 - rhombic lip. Roman numerals indicate the origin of the cranial nerves.

Rice. 48. The developing brain (from the 3rd to the 7th week of development).


At the beginning, the surface of the cerebral hemispheres is smooth. At 11-12 weeks of intrauterine development, the lateral sulcus (Sylvius) is formed first, then the central (Rollandian) sulcus. The laying of grooves within the lobes of the hemispheres occurs quite quickly; due to the formation of grooves and convolutions, the area of ​​the cortex increases (Fig. 49).

Rice. 49. Side view of the developing cerebral hemispheres.

A- 11th week. B- 16_ 17 weeks. B- 24-26 weeks. G- 32-34 weeks. D - newborn. The formation of the lateral fissure (5), the central sulcus (7) and other sulci and convolutions is shown.

I - telencephalon; 2 - midbrain; 3 - cerebellum; 4 - medulla oblongata; 7 - central groove; 8 - bridge; 9 - grooves of the parietal region; 10 - grooves of the occipital region;

II - furrows of the frontal region.

By migration, neuroblasts form clusters - nuclei that form the gray matter of the spinal cord, and in the brain stem - some nuclei of the cranial nerves.

Neuroblast somata have a round shape. The development of a neuron is manifested in the appearance, growth and branching of processes (Fig. 50). A small short protrusion forms on the neuron membrane at the site of the future axon - a growth cone. The axon extends and delivers nutrients to the growth cone. At the beginning of development, a neuron develops a larger number of processes compared to the final number of processes of a mature neuron. Some of the processes are retracted into the soma of the neuron, and the remaining ones grow towards other neurons with which they form synapses.

Rice. 50. Development of a spindle-shaped cell in human ontogenesis. The last two sketches show the difference in the structure of these cells in a child aged two years and an adult


In the spinal cord, axons are short in length and form intersegmental connections. Longer projection fibers form later. Somewhat later than the axon, dendritic growth begins. All branches of each dendrite are formed from one trunk. The number of branches and length of dendrites is not completed in the prenatal period.

The increase in brain mass during the prenatal period occurs mainly due to an increase in the number of neurons and the number of glial cells.

The development of the cortex is associated with the formation of cellular layers (in the cerebellar cortex there are three layers, and in the cerebral cortex there are six layers).

The so-called glial cells play an important role in the formation of the cortical layers. These cells take a radial position and form two vertically oriented long processes. Neuronal migration occurs along the processes of these radial glial cells. The more superficial layers of the bark are formed first. Glial cells also take part in the formation of the myelin sheath. Sometimes one glial cell participates in the formation of the myelin sheaths of several axons.

Table 2 reflects the main stages of development of the nervous system of the embryo and fetus.


Table 2.

The main stages of development of the nervous system in the prenatal period.

Fetal age (weeks) Nervous system development
2,5 A neural groove is outlined
3.5 The neural tube and nerve cords are formed
4 3 brain bubbles are formed; nerves and ganglia form
5 5 brain bubbles form
6 The meninges are outlined
7 The hemispheres of the brain reach a large size
8 Typical neurons appear in the cortex
10 The internal structure of the spinal cord is formed
12 General structural features of the brain are formed; differentiation of neuroglial cells begins
16 Distinct lobes of the brain
20-40 Myelination of the spinal cord begins (week 20), layers of the cortex appear (week 25), sulci and convolutions form (week 28-30), myelination of the brain begins (week 36-40)

Thus, the development of the brain in the prenatal period occurs continuously and in parallel, but is characterized by heterochrony: the rate of growth and development of phylogenetically older formations is greater than that of phylogenetically younger formations.

Genetic factors play a leading role in the growth and development of the nervous system during the prenatal period. The average weight of a newborn's brain is approximately 350 g.

Morpho-functional maturation of the nervous system continues in the postnatal period. By the end of the first year of life, the weight of the brain reaches 1000 g, while in an adult the brain weight is on average 1400 g. Consequently, the main increase in brain mass occurs in the first year of a child’s life.

The increase in brain mass in the postnatal period occurs mainly due to an increase in the number of glial cells. The number of neurons does not increase, since they lose the ability to divide already in the prenatal period. The overall density of neurons (the number of cells per unit volume) decreases due to the growth of the soma and processes. The number of branches of dendrites increases.

In the postnatal period, myelination of nerve fibers also continues both in the central nervous system and the nerve fibers that make up the peripheral nerves (cranial and spinal).

The growth of spinal nerves is associated with the development of the musculoskeletal system and the formation of neuromuscular synapses, and the growth of cranial nerves with the maturation of sensory organs.

Thus, if in the prenatal period the development of the nervous system occurs under the control of the genotype and practically does not depend on the influence of the external environment, then in the postnatal period external stimuli become increasingly important. Irritation of the receptors causes afferent impulse flows that stimulate the morpho-functional maturation of the brain.

Under the influence of afferent impulses, spines are formed on the dendrites of cortical neurons - outgrowths that are special postsynaptic membranes. The more spines, the more synapses and the more involved the neuron is in information processing.

Throughout postnatal ontogenesis up to puberty, as well as in the prenatal period, brain development occurs heterochronously. Thus, the final maturation of the spinal cord occurs earlier than the brain. The development of stem and subcortical structures, earlier than the cortical ones, the growth and development of excitatory neurons overtakes the growth and development of inhibitory neurons. These are general biological patterns of growth and development of the nervous system.

Morphological maturation of the nervous system correlates with the characteristics of its functioning at each stage of ontogenesis. Thus, earlier differentiation of excitatory neurons compared to inhibitory neurons ensures the predominance of flexor muscle tone over extensor tone. The arms and legs of the fetus are in a bent position - this determines a position that provides minimal volume, due to which the fetus takes up less space in the uterus.

Improving the coordination of movements associated with the formation of nerve fibers occurs throughout the preschool and school periods, which is manifested in the consistent development of sitting, standing, walking, writing, etc. postures.

The increase in the speed of movements is caused mainly by the processes of myelination of peripheral nerve fibers and an increase in the speed of excitation of nerve impulses.

The earlier maturation of subcortical structures compared to cortical ones, many of which are part of the limbic structure, determines the characteristics of the emotional development of children (greater intensity of emotions and the inability to restrain them are associated with the immaturity of the cortex and its weak inhibitory influence).

In old age and senility, anatomical and histological changes in the brain occur. Atrophy of the cortex of the frontal and superior parietal lobes often occurs. The fissures become wider, the ventricles of the brain enlarge, and the volume of white matter decreases. Thickening of the meninges occurs.

With age, neurons decrease in size, but the number of nuclei in cells may increase. In neurons, the content of RNA necessary for the synthesis of proteins and enzymes also decreases. This impairs the trophic functions of neurons. It has been suggested that such neurons fatigue more quickly.

In old age, the blood supply to the brain is also disrupted, the walls of blood vessels thicken and cholesterol plaques are deposited on them (atherosclerosis). It also impairs the functioning of the nervous system.

LITERATURE

Atlas “Human Nervous System”. Comp. V.M. Astashev. M., 1997.

Blum F., Leiserson A., Hofstadter L. Brain, mind and behavior. M.: Mir, 1988.

Borzyak E.I., Bocharov V.Ya., Sapina M.R. Human anatomy. - M.: Medicine, 1993. T.2. 2nd ed., revised. and additional

Zagorskaya V.N., Popova N.P. Anatomy of the nervous system. Course program. MOSU, M., 1995.

Kishsh-Sentagotai. Anatomical atlas of the human body. - Budapest, 1972. 45th edition. T. 3.

Kurepina M.M., Vokken G.G. Human anatomy. - M.: Education, 1997. Atlas. 2nd edition.

Krylova N.V., Iskrenko I.A. Brain and pathways (Human anatomy in diagrams and drawings). M.: Publishing house of the Russian Peoples' Friendship University, 1998.

Brain. Per. from English Ed. Simonova P.V. - M.: Mir, 1982.

Human morphology. Ed. B.A. Nikityuk, V.P. Chtetsova. - M.: Moscow State University Publishing House, 1990. P. 252-290.

Prives M.G., Lysenkov N.K., Bushkovich V.I. Human anatomy. - L.: Medicine, 1968. P. 573-731.

Savelyev S.V. Stereoscopic atlas of the human brain. M., 1996.

Sapin M.R., Bilich G.L. Human anatomy. - M.: Higher School, 1989.

Sinelnikov R.D. Atlas of human anatomy. - M.: Medicine, 1996. 6th ed. T. 4.

Schade J., Ford D. Fundamentals of Neurology. - M.: Mir, 1982.


Tissue is a collection of cells and intercellular substance that are similar in structure, origin and functions.

Some anatomists do not include the medulla oblongata in the hindbrain, but distinguish it as an independent section.