Body position analyzers include: Adaptation of pain receptors. III. New topic

DEFINITION

Analyzer- a functional unit responsible for the perception and analysis of sensory information of one type (the term was introduced by I.P. Pavlov).

The analyzer is a set of neurons involved in the perception of stimuli, the conduction of excitation and the analysis of stimulation.

The analyzer is often called sensory system. Analyzers are classified according to the type of sensations in the formation of which they participate (see figure below).

Rice. Analyzers

This visual, auditory, vestibular, gustatory, olfactory, cutaneous, muscular and other analyzers. The analyzer has three sections:

1. Peripheral department: a receptor designed to convert the energy of stimulation into the process of nervous excitation.
2. Wiring department: a chain of centripetal (afferent) and intercalary neurons through which impulses are transmitted from receptors to the overlying parts of the central nervous system.
3. Central department: a specific area of ​​the cerebral cortex.

In addition to the ascending (afferent) pathways, there are descending fibers (efferent), through which the activity of the lower levels of the analyzer is regulated by its higher, especially cortical, sections.

analyzer	peripheral section (sensory organ and receptors)	conductor department	central department
visual	retinal receptors	optic nerve	visual center in the occipital lobe of the KBP
auditory	sensory hair cells of the organ of Corti (spiral) organ of the cochlea	auditory nerve	auditory center in the temporal lobe
olfactory	olfactory receptors of the nasal epithelium	olfactory nerve	olfactory center in the temporal lobe
gustatory	taste buds oral cavity(mostly the root of the tongue)	glossopharyngeal nerve	taste center in the temporal lobe
tactile (tactile)	tactile corpuscles of the papillary dermis (pain, temperature, tactile and other receptors)	centripetal nerves; spinal cord, medulla oblongata, diencephalon	center of skin sensitivity in the central gyrus of the parietal lobe of the KBP
musculocutaneous	proprioceptors in muscles and ligaments	centripetal nerves; spinal cord; medulla oblongata and diencephalon	motor zone and adjacent areas of the frontal and parietal lobes.
vestibular	semicircular canaliculi and vestibule of the inner ear	vestibulocochlear nerve (VIII pair of cranial nerves)	cerebellum

KBP*- cerebral cortex.

sense organs

A person has a number of important specialized peripheral formations - sense organs, providing the perception of influences on the body external stimuli.

The sense organ consists of receptors And auxiliary apparatus, which helps to capture, concentrate, focus, direct, etc. signal.

The sense organs include the organs of vision, hearing, smell, taste, and touch. By themselves they cannot provide sensation. For a subjective sensation to arise, it is necessary that the excitation that arises in the receptors enters the corresponding section of the cerebral cortex.

Structural fields of the cerebral cortex

If we consider the structural organization of the cerebral cortex, we can distinguish several fields with different cellular structures.

There are three main groups of fields in the cortex:

• primary
• secondary
• tertiary

Primary fields, or nuclear zones of the analyzers, are directly connected with the senses and organs of movement.

For example, the field of pain, temperature, musculocutaneous sensitivity in the posterior part of the central gyrus, the visual field in the occipital lobe, the auditory field in the temporal lobe and the motor field in the anterior part of the central gyrus.

Primary fields mature earlier than others in ontogenesis.

Function of primary fields: analysis of individual stimuli entering the cortex from the corresponding receptors.

When the primary fields are destroyed, so-called cortical blindness, cortical deafness, etc. occur.

Secondary fields located next to the primary ones and connected through them with the sense organs.

Function of secondary fields: generalization and further processing of incoming information. Individual sensations are synthesized in them into complexes that determine the processes of perception.

When secondary fields are damaged, a person sees and hears, but unable to comprehend understand the meaning of what you see and hear.

Both humans and animals have primary and secondary fields.

Tertiary fields, or overlap areas of analyzers, are located in the posterior half of the cortex - on the border of the parietal, temporal and occipital lobes and in the anterior parts of the frontal lobes. They occupy half of the entire area of ​​the cerebral cortex and have numerous connections with all its parts.Most of the nerve fibers connecting the left and right hemispheres end in the tertiary fields.

Function of tertiary fields: organization of coordinated work of both hemispheres, analysis of all perceived signals, their comparison with previously received information, coordination of appropriate behavior,programming of motor activity.

These fields are found only in humans and mature later than other cortical fields.

The development of tertiary fields in humans is associated with the function of speech. Thinking (inner speech) is possible only with the joint activity of analyzers, the integration of information from which occurs in tertiary fields.

With congenital underdevelopment of the tertiary fields, a person is not able to master speech and even the simplest motor skills.

Rice. Structural fields of the cerebral cortex

Taking into account the location of the structural fields of the cerebral cortex, functional parts can be distinguished: sensory, motor and associative areas.

All sensory and motor areas occupy less than 20% of the surface of the cortex. The rest of the cortex constitutes the association region.

Association zones

Association zones- This functional areas cerebral cortex. They connect newly received sensory information with previously received and stored in memory blocks, and also compare information received from different receptors (see figure below).

Each associative area of ​​the cortex is associated with several structural fields. The association zones include part of the parietal, frontal and temporal lobes. The boundaries of the associative zones are unclear; its neurons are involved in the integration of various information. Here comes the highest analysis and synthesis of irritations. As a result, complex elements of consciousness are formed.

Rice. Sulci and lobes of the cerebral cortex

Rice. Association areas of the cerebral cortex:

1. Ass motivating engine nal zone(frontal lobe)

2. Primary motor area

3. Primary somatosensory area

4. Parietal lobe of the cerebral hemispheres

5. Associative somatosensory (musculocutaneous) zone(parietal lobe)

6.Association visual area(occipital lobe)

7. Occipital lobe of the cerebral hemispheres

8. Primary visual area

9. Association auditory area(temporal lobes)

10. Primary auditory zone

11. Temporal lobe of the cerebral hemispheres

12. Olfactory cortex (inner surface of the temporal lobe)

13. Gustatory bark

14. Prefrontal association area

15. Frontal lobe of the cerebral hemispheres.

Sensory signals in the association zone are deciphered, interpreted and used to determine the most appropriate responses, which are transmitted to the associated motor (motor) zone.

Thus, associative zones are involved in the processes of memorization, learning and thinking, and the results of their activity constitute intelligence(the body’s ability to use acquired knowledge).

Individual large association areas are located in the cortex next to the corresponding sensory areas. For example, the visual association area is located in the occipital area immediately anterior to the sensory area. visual area and carries out complete processing of visual information.

Some association areas perform only part of the information processing and are connected to other association centers that perform further processing. For example, the auditory association area analyzes sounds, categorizing them, and then transmits signals to more specialized areas, such as the speech association area, where the meaning of words heard is perceived.

These zones belong to association cortex and participate in the organization of complex forms of behavior.

In the cerebral cortex, areas with less defined functions are distinguished. Thus, a significant part of the frontal lobes, especially on the right side, can be removed without noticeable damage. However, if a bilateral removal of the frontal areas is performed, severe mental disorders occur.

taste analyzer

Taste analyzer responsible for the perception and analysis of taste sensations.

Peripheral department: receptors - taste buds in the mucous membrane of the tongue, soft palate, tonsils and other organs of the oral cavity.

Rice. 1. Taste bud and taste bud

Taste buds bear taste buds on the lateral surface (Fig. 1, 2), which include 30 - 80 sensitive cells. Taste cells are dotted at their ends with microvilli - taste hairs. They come to the surface of the tongue through the taste pores. Taste cells continually divide and continually die. The replacement of cells located in the front part of the tongue, where they lie more superficially, occurs especially quickly.

Rice. 2. Taste bud: 1 - nerve taste fibers; 2 - taste bud (calyx); 3 - taste cells; 4 - supporting (supporting) cells; 5 - taste time

Rice. 3. Taste zones of the tongue: sweet - tip of the tongue; bitter - the base of the tongue; sour - side surface language; salty - tip of the tongue.

Taste sensations are caused only by substances dissolved in water.

Wiring department: fibers of the facial and glossopharyngeal nerve (Fig. 4).

Central department: inner side temporal lobe of the cerebral cortex.

olfactory analyzer

Olfactory analyzer responsible for the perception and analysis of smell.

• eating behavior;
• food testing for edibility;
• setting up the digestive system to process food (according to the mechanism of a conditioned reflex);
• defensive behavior (including manifestations of aggression).

Peripheral department: receptors in the mucous membrane of the upper part of the nasal cavity. Olfactory receptors in the nasal mucosa end in olfactory cilia. Gaseous substances dissolve in the mucus surrounding the cilia, then as a result chemical reaction a nerve impulse occurs (Fig. 5).

Wiring department: olfactory nerve.

Central department: olfactory bulb (the structure of the forebrain in which information is processed) and the olfactory center located on the lower surface of the temporal and frontal lobes of the cerebral cortex (Fig. 6).

In the cortex, the smell is detected and the body’s adequate response to it is formed.

The perception of taste and smell complement each other, giving a holistic picture of the appearance and quality of food. Both analyzers are connected to the salivary center of the medulla oblongata and participate in the body’s nutritional reactions.

The tactile and muscle analyzers are combined into somatosensory system- system of musculoskeletal sensitivity.

Structure of the somatosensory analyzer

Peripheral department: proprioceptors of muscles and tendons; skin receptors ( mechanoreceptors, thermoreceptors, etc.).

Wiring department: afferent (sensitive) neurons; ascending tracts of the spinal cord; medulla oblongata, diencephalon nuclei.

Central department: sensory area in the parietal lobe of the cerebral cortex.

Skin receptors

The skin is the largest sensory organ in the human body. Many receptors are concentrated on its surface (about 2 m2).

Most scientists tend to believe that there are four main types of skin sensitivity: tactile, thermal, cold and pain.

Receptors are distributed unevenly and at different depths. Most of the receptors are in the skin of the fingers, palms, soles, lips and genitals.

MECHANORECEPTORS OF THE SKIN

• thin nerve fiber endings, entwining blood vessels, hair follicles, etc.
• Merkel cells- nerve endings of the basal layer of the epidermis (many on the fingertips);
• tactile Meissner corpuscles- complex receptors of the papillary dermis (many on the fingers, palms, soles, lips, tongue, genitals and nipples of the mammary glands);
• lamellar bodies- pressure and vibration receptors; located in the deep layers of the skin, in tendons, ligaments and mesentery;
• bulbs (Krause flasks)- nerve receptors inconnective tissue layer of mucous membranes, under the epidermis and among the muscle fibers of the tongue.

MECHANISM OF OPERATION OF MECHANORECEPTORS

Mechanical stimulus - deformation of the receptor membrane - decrease in the electrical resistance of the membrane - increase in membrane permeability for Na+ - depolarization of the receptor membrane - propagation of the nerve impulse

ADAPTATION OF SKIN MECHANORECEPTORS

• rapidly adapting receptors: skin mechanoreceptors in hair follicles, lamellar bodies (we do not feel the pressure of clothing, contact lenses, etc.);
• slow adapting receptors:tactile Meissner corpuscles.

The sensation of touch and pressure on the skin is quite accurately localized, that is, a person refers to a specific area of ​​the skin surface. This localization is developed and consolidated in ontogenesis with the participation of vision and proprioception.

A person’s ability to separately perceive touch on two adjacent points of the skin also differs greatly in different areas of the skin. On the mucous membrane of the tongue, the threshold of spatial difference is 0.5 mm, and on the skin of the back - more than 60 mm.

Temperature reception

The human body temperature fluctuates within relatively narrow limits, so information about the ambient temperature necessary for the functioning of thermoregulatory mechanisms is especially important.

Thermoreceptors are located in the skin, cornea, mucous membranes, and also in the central nervous system (hypothalamus).

TYPES OF THERMORECEPTORS

• cold thermoreceptors: numerous; lie close to the surface.
• thermal thermoreceptors: there are significantly fewer of them; lie in a deeper layer of skin.

• specific thermoreceptors: perceive only temperature;
• nonspecific thermoreceptors: perceive temperature and mechanical stimuli.

Thermoreceptors respond to temperature changes by increasing the frequency of generated impulses, which last steadily throughout the duration of the stimulus. A temperature change of 0.2 °C causes long-term changes in their impulses.

Under some conditions, cold receptors can be excited by heat, and thermal receptors by cold. This explains the acute sensation of cold when quickly immersed in a hot bath or the scalding effect of ice water.

The initial temperature sensations depend on the difference in skin temperature and the temperature of the active stimulus, its area and place of application. So, if the hand was held in water at a temperature of 27 °C, then at the first moment when the hand is transferred to water heated to 25 °C, it seems cold, but after a few seconds a true assessment of the absolute temperature of the water becomes possible.

Pain reception

Pain sensitivity is of paramount importance for the survival of the body, being a signal of danger under strong influences of various factors.

Impulses from pain receptors often indicate pathological processes in the body.

On this moment No specific pain receptors were found.

Two hypotheses about the organization of pain perception have been formulated:

1. Exist specific pain receptors - free nerve endings with a high reaction threshold;
2. Specific pain receptors does not exist; pain occurs when any receptors are overly stimulated.

The mechanism of receptor excitation during painful stimuli has not yet been clarified.

The most common cause of pain can be considered a change in H+ concentration due to toxic effects on respiratory enzymes or damage to cell membranes.

One of the possible causes of prolonged burning pain may be the release of histamine, proteolytic enzymes and other substances that cause a chain of biochemical reactions leading to excitation of nerve endings when cells are damaged.

Pain sensitivity is practically not represented at the cortical level, therefore the highest center of pain sensitivity is the thalamus, where 60% of neurons in the corresponding nuclei clearly react to painful stimulation.

ADAPTATION OF PAIN RECEPTORS

Adaptation of pain receptors depends on numerous factors and its mechanisms are poorly understood.

For example, a splinter, being motionless, does not cause much pain. Elderly people in some cases “get used to not noticing” headaches or joint pain.

However, in many cases, pain receptors do not show significant adaptation, which makes the patient’s suffering especially long and painful and requires the use of analgesics.

Painful stimuli cause a number of reflex somatic and autonomic reactions. When moderately expressed, these reactions have adaptive significance, but can lead to severe pathological effects, such as shock. Among these reactions are an increase in muscle tone, heart rate and respiration, an increase or decrease in blood pressure, constriction of the pupils, an increase in blood glucose and a number of other effects.

LOCALIZATION OF PAIN SENSITIVITY

In case of painful effects on the skin, a person localizes them quite accurately, but in case of diseases internal organs may arise referred pain. For example, with renal colic, patients complain of “incoming” sharp pain in the legs and rectum. There may also be reverse effects.

proprioception

Types of proprioceptors:

• neuromuscular spindles: provide information about the speed and force of muscle stretch and contraction;
• Golgi tendon receptors: provide information about the force of muscle contraction.

Functions of proprioceptors:

• perception of mechanical irritations;
• perception of the spatial arrangement of body parts.

NEUROMUSCULAR SPINDLE

Neuromuscular spindle- a complex receptor that includes modified muscle cells, afferent and efferent nerve processes and controls both the speed and degree of contraction and stretching of skeletal muscles.

The neuromuscular spindle is located deep within the muscle. Each spindle is covered with a capsule. Inside the capsule there is a bundle of special muscle fibers. The spindles are located parallel to the fibers of skeletal muscles, so when the muscle is stretched, the load on the spindles increases, and when it contracts, it decreases.

Rice. Neuromuscular spindle

GOLGI TENDON RECEPTORS

They are located in the area where the muscle fibers connect with the tendon.

Tendon receptors react weakly to muscle stretching, but are excited when it contracts. The intensity of their impulses is approximately proportional to the force of muscle contraction.

Rice. Golgi tendon receptor

JOINT RECEPTORS

They have been studied less than muscle ones. It is known that articular receptors respond to the position of the joint and to changes in the joint angle, thus participating in the feedback system from the motor system and in its control.

The visual analyzer includes:

• peripheral: retinal receptors;
• conduction section: optic nerve;
• central section: occipital lobe of the cerebral cortex.

Visual analyzer function: perception, conduction and decoding of visual signals.

Structures of the eye

The eye consists of eyeball And auxiliary apparatus.

Accessory eye apparatus

• brows- protection from sweat;
• eyelashes- protection from dust;
• eyelids - mechanical protection and maintaining humidity;
• lacrimal glands- located at the upper part of the outer edge of the orbit. It secretes tear fluid that moisturizes, washes and disinfects the eye. Excess tear fluid is removed into the nasal cavity through tear duct, located in inner corner eye sockets .

EYEBALL

The eyeball is roughly spherical in shape with a diameter of about 2.5 cm.

It is located on a cushion of fatin the anterior part of the orbit.

The eye has three membranes:

1. tunica albuginea ( sclera) with a transparent cornea- outer very dense fibrous membrane of the eye;
2. choroid with outer iris and ciliary body- penetrated by blood vessels (nutrition of the eye) and contains a pigment that prevents the scattering of light through the sclera;
3. retina (retina) - inner lining of the eyeball -receptor part of the visual analyzer; function: direct perception of light and transmission of information to the central nervous system.

Conjunctiva- mucous membrane connecting the eyeball to the skin.

Tunica albuginea (sclera)- durable outer shell of the eye; inner part The sclera is impenetrable to set rays. Function: eye protection from external influences and light insulation;

Cornea- anterior transparent part of the sclera; is the first lens on the path of light rays. Function: mechanical protection of the eye and transmission of light rays.

Lens- a biconvex lens located behind the cornea. Function of the lens: focusing light rays. The lens has no blood vessels or nerves. Inflammatory processes do not develop in it. It contains many proteins, which can sometimes lose their transparency, leading to a disease called cataract.

Choroid- the middle layer of the eye, rich in blood vessels and pigment.

Iris- anterior pigmented part of the choroid; contains pigments melanin And lipofuscin, determining eye color.

Pupil - round hole in the iris. Function: regulation of light flow entering the eye. Pupil diameter changes involuntarily with the help of smooth muscles of the iriswhen lighting changes.

Front and rear cameras- space in front and behind the iris filled with clear liquid ( aqueous humor).

Ciliary (ciliary) body- part of the middle (choroid) membrane of the eye; function: fixation of the lens, ensuring the process of accommodation (change in curvature) of the lens; production of aqueous humor in the chambers of the eye, thermoregulation.

Vitreous body- the cavity of the eye between the lens and the fundus of the eye , filled with a transparent viscous gel that maintains the shape of the eye.

Retina (retina)- receptor apparatus of the eye.

STRUCTURE OF THE RETINA

The retina is formed by the branches of the endings of the optic nerve, which, approaching the eyeball, passes through the tunica albuginea, and the sheath of the nerve merges with the tunica albuginea of ​​the eye. Inside the eye, the nerve fibers are distributed in the form of a thin mesh membrane that lines the back 2/3 of the inner surface of the eyeball.

The retina is made up of supporting cells that form a mesh-like structure, hence its name. Only its back part perceives light rays. The retina, in its development and function, is part of the nervous system. However, the remaining parts of the eyeball play a supporting role in the retina’s perception of visual stimuli.

Retina- this is the part of the brain that is pushed outward, closer to the surface of the body, and maintains a connection with it through a pair of optic nerves.

Nerve cells form chains in the retina consisting of three neurons (see figure below):

• the first neurons have dendrites in the form of rods and cones; these neurons are the terminal cells of the optic nerve; they perceive visual stimuli and are light receptors.
• the second - bipolar neurons;
• the third are multipolar neurons ( ganglion cells); Axons extend from them, which stretch along the bottom of the eye and form the optic nerve.

Photosensitive elements of the retina:

• sticks- perceive brightness;
• cones- perceive color.

The cones are excited slowly and only by bright light. They are able to perceive color. There are three types of cones in the retina. The first perceive the color red, the second - green, the third - blue. Depending on the degree of excitation of the cones and the combination of irritations, the eye perceives different colors and shades.

The rods and cones in the retina of the eye are mixed together, but in some places they are very densely located, in others they are rare or absent altogether. For each nerve fiber there are approximately 8 cones and about 130 rods.

In area macular spot There are no rods on the retina - only cones; here the eye has the greatest visual acuity and the best color perception. Therefore, the eyeball is in continuous motion, so that the part of the object being examined falls on the macula. As you move away from the macula, the density of the rods increases, but then decreases.

In low light, only rods are involved in the vision process (twilight vision), and the eye does not distinguish colors, vision turns out to be achromatic (colorless).

Nerve fibers extend from the rods and cones, which unite to form the optic nerve. The place where the optic nerve exits the retina is called optic disc. There are no photosensitive elements in the area of ​​the optic nerve head. Therefore, this place does not give a visual sensation and is called blind spot.

EYE MUSCLES

• oculomotor muscles- three pairs of striated skeletal muscles that are attached to the conjunctiva; carry out movement of the eyeball;
• pupil muscles- smooth muscles of the iris (circular and radial), changing the diameter of the pupil;
  The circular muscle (contractor) of the pupil is innervated by parasympathetic fibers from the oculomotor nerve, and the radial muscle (dilator) of the pupil is innervated by fibers of the sympathetic nerve. The iris thus regulates the amount of light entering the eye; in strong, bright light, the pupil narrows and limits the entry of rays, and in weak light, it expands, allowing more rays to penetrate. The diameter of the pupil is influenced by the hormone adrenaline. When a person is in an excited state (fear, anger, etc.), the amount of adrenaline in the blood increases, and this causes the pupil to dilate.
  The movements of the muscles of both pupils are controlled from one center and occur synchronously. Therefore, both pupils always dilate or contract equally. Even if you apply bright light to only one eye, the pupil of the other eye also narrows.
• lens muscles(ciliary muscles) - smooth muscles that change the curvature of the lens ( accommodation--focusing the image on the retina).

Wiring department

The optic nerve conducts light stimuli from the eye to the visual center and contains sensory fibers.

Moving away from the posterior pole of the eyeball, the optic nerve leaves the orbit and, entering the cranial cavity, through the optic canal, together with the same nerve on the other side, forms a chiasm ( chiasmus) under the hypolalamus. After the chiasm, the optic nerves continue in visual tracts. The optic nerve is connected to the nuclei of the diencephalon, and through them to the cerebral cortex.

Each optic nerve contains the totality of all the processes of the nerve cells of the retina of one eye. In the area of ​​the chiasm, an incomplete crossover of fibers occurs, and each optic tract contains about 50% of the fibers of the opposite side and the same number of fibers of the same side.

Central department

The central section of the visual analyzer is located in the occipital lobe of the cerebral cortex.

Impulses from light stimuli travel along the optic nerve to the cerebral cortex of the occipital lobe, where the visual center is located.

The fibers of each nerve are connected to the two hemispheres of the brain, and the image obtained on the left half of the retina of each eye is analyzed in the visual cortex of the left hemisphere, and on the right half of the retina - in the cortex of the right hemisphere.

visual impairment

With age and under the influence of other reasons, the ability to control the curvature of the lens surface weakens.

Myopia (myopia)- focusing the image in front of the retina; develops due to an increase in the curvature of the lens, which can occur due to improper metabolism or poor visual hygiene. AND use glasses with concave lenses.

Farsightedness- focusing the image behind the retina; occurs due to a decrease in the convexity of the lens. ANDcope with glasseswith convex lenses.

There are two ways to conduct sounds:

• air conduction: through the external auditory canal, eardrum and chain of auditory ossicles;
• tissue conductivity b: through the tissues of the skull.

Function of the auditory analyzer: perception and analysis of sound stimuli.

Peripheral: auditory receptors in the inner ear cavity.

Conductor section: auditory nerve.

Central division: auditory zone in the temporal lobe of the cerebral cortex.

Rice. Temporal bone Fig. Location of the hearing organ in the cavity of the temporal bone

ear structure

The human hearing organ is located in the cranial cavity in the thickness of the temporal bone.

It is divided into three sections: the outer, middle and inner ear. These departments are closely connected anatomically and functionally.

Outer ear consists of the external auditory canal and the auricle.

Middle ear- tympanic cavity; it is separated from the outer ear by the eardrum.

Inner ear, or labyrinth, - the section of the ear where irritation of the receptors of the auditory (cochlear) nerve occurs; it is placed inside the pyramid of the temporal bone. The inner ear forms the organ of hearing and balance.

The outer and middle ears are of secondary importance: they conduct sound vibrations to the inner ear, and are thus a sound-conducting apparatus.

Rice. Ear sections

EXTERNAL EAR

Outer ear includes auricle And external auditory canal, which are designed to capture and conduct sound vibrations.

Auricle formed by three tissues:

• a thin plate of hyaline cartilage, covered on both sides with perichondrium, having a complex convex-concave shape that determines the relief of the auricle;
• the skin is very thin, tightly adjacent to the perichondrium and has almost no fatty tissue;
• subcutaneous fatty tissue, located in significant quantities in the lower part of the auricle - earlobe.

The auricle is attached to the temporal bone by ligaments and has vestigial muscles that are well defined in animals.

The auricle is designed to concentrate sound vibrations as much as possible and direct them into the external auditory opening.

The shape, size, position of the auricle and the size of the ear lobe are individual for each person.

Darwin's tubercle- a rudimentary triangular protrusion, which is observed in 10% of people in the superior-posterior region of the conchal helix; it corresponds to the top of the animal's ear.

Rice. Darwin's tubercle

External auditory passage is an S-shaped tube approximately 3 cm long and 0.7 cm in diameter, which opens externally with the auditory opening and is separated from the middle ear cavity eardrum.

The cartilaginous part, which is a continuation of the cartilage of the auricle, makes up 1/3 of its length, the remaining 2/3 is formed by the bone canal of the temporal bone. At the point where the cartilaginous section transitions into the bone canal, it narrows and bends. In this place there is a ligament of elastic connective tissue. This structure makes it possible to stretch the cartilaginous part of the passage in length and width.

In the cartilaginous part of the ear canal, the skin is covered with short hairs that protect against small particles from entering the ear. The sebaceous glands open into the hair follicles. Characteristic of the skin of this section is the presence of sulfur glands in the deeper layers.

Sulfur glands are derivatives of the sweat glands. Sulfur glands drain either into the hair follicles or freely into the skin. The sulfur glands secrete a light yellow secretion, which, together with the secretion of the sebaceous glands and the rejected epithelium, forms earwax.

Earwax- light yellow secretion of the sulfur glands of the external auditory canal.

Sulfur consists of proteins, fats, fatty acids and mineral salts. Some proteins are immunoglobulins that determine protective function. In addition, sulfur contains dead cells, sebum, dust and other inclusions.

Function of earwax:

• moisturizing the skin of the external auditory canal;
• cleaning the ear canal from foreign particles (dust, litter, insects);
• protection against bacteria, fungi and viruses;
• grease in the outer part of the ear canal prevents water from entering it.

Earwax, along with impurities, is naturally removed from the ear canal through chewing movements and speech. In addition, the skin of the ear canal is constantly renewed and grows outward from the ear canal, taking wax with it.

Interior bone section The external auditory canal is a canal of the temporal bone that ends in the eardrum. In the middle of the bone section there is a narrowing of the auditory canal - the isthmus, behind which there is a wider area.

The skin of the bony part is thin, does not contain hair follicles and glands and extends onto the eardrum, forming its outer layer.

Eardrum represents thin oval (11 x 9 mm) translucent plate, impermeable to water and air. Membraneconsists of elastic and collagen fibers, which in its upper part are replaced by fibers of loose connective tissue.On the side of the auditory canal, the membrane is covered with flat epithelium, and on the side of the tympanic cavity - with mucosal epithelium.

In the central part, the eardrum is concave; the handle of the malleus, the first auditory ossicle of the middle ear, is attached to it from the side of the tympanic cavity.

The eardrum begins and develops along with the organs of the outer ear.

MIDDLE EAR

The middle ear includes a mucous membrane lined and filled with air tympanic cavity(volume about 1 Withm3 cm3), three auditory ossicles and auditory (Eustachian) tube.

Rice. Middle ear

Tympanic cavity located in the thickness of the temporal bone, between the eardrum and the bony labyrinth. The tympanic cavity contains the auditory ossicles, muscles, ligaments, blood vessels and nerves. The walls of the cavity and all the organs located in it are covered with a mucous membrane.

In the septum separating the tympanic cavity from the inner ear, there are two windows:

• oval window: located in the upper part of the septum, leads to the vestibule of the inner ear; closed by the base of the stapes;
• round window: located in lower part of the septum, leads to the beginning of the cochlea; closed by the secondary tympanic membrane.

There are three auditory ossicles in the tympanic cavity: malleus, incus and stapes (= stapes). The auditory ossicles are small. Connecting with each other, they form a chain that stretches from the eardrum to the oval opening. All bones are connected to each other using joints and are covered with a mucous membrane.

Hammer the handle is fused with the eardrum, and the head is connected to the anvil, which in turn is movably connected to stirrup. The base of the stapes covers the oval window of the vestibule.

The muscles of the tympanic cavity (tensor tympani and stapedius) keep the auditory ossicles in a state of tension and protect the inner ear from excessive sound stimulation.

Auditory (Eustachian) tube connects the tympanic cavity of the middle ear with the nasopharynx. This a muscular tube that opens when swallowing and yawning.

The mucous membrane lining the auditory tube is a continuation of the mucous membrane of the nasopharynx and consists of ciliated epithelium with the movement of cilia from the tympanic cavity to the nasopharynx.

Functions of the Eustachian tube:

• balancing the pressure between the tympanic cavity and the external environment to maintain normal operation of the sound-conducting apparatus;
• protection against infections;
• removal of accidentally penetrated particles from the tympanic cavity.

INNER EAR

The inner ear consists of a bony labyrinth and a membranous labyrinth inserted into it.

Bone labyrinth consists of three departments: vestibule, cochlea And three semicircular canals.

vestibule- cavity small sizes and irregularly shaped outer wall which has two windows (round and oval) leading into the tympanic cavity. The anterior part of the vestibule communicates with the cochlea through the scala vestibule. The back part contains two impressions for the vestibular sacs.

Snail- bone spiral channel of 2.5 turns. The axis of the cochlea lies horizontally and is called the bony cochlear shaft. A bone spiral plate wraps around the rod, which partially blocks the spiral canal of the cochlea and divides it on staircase vestibule And staircase drum. They communicate with each other only through a hole located at the top of the cochlea.

Rice. Structure of the cochlea: 1 - basement membrane; 2 - organ of Corti; 3 - Reisner membrane; 4 - staircase vestibule; 5 - spiral ganglion; 6 - scala tympani; 7 - vestibular-helical nerve; 8 - spindle.

Semicircular canals- bone formations located in three mutually perpendicular planes. Each channel has an expanded stalk (ampule).

Rice. Cochlea and semicircular canals

Membranous labyrinth filled endolymph And consists of three departments:

• membranous snail, orcochlear duct,continuation of the spiral plate between the scala vestibule and the scala tympani. The cochlear duct contains auditory receptors -spiral, or organ of Corti;
• three semicircular canals and two pouches located in the vestibule, which play the role of the vestibular apparatus.

Between the bony and membranous labyrinth there is perilymph--modified cerebrospinal fluid.

organ of corti

On the plate of the cochlear duct, which is a continuation of the bony spiral plate, there is organ of Corti (spiral).

The spiral organ is responsible for the perception of sound stimuli. It acts as a microphone, transforming mechanical vibrations into electrical ones.

The organ of Corti consists of supporting and sensory hair cells.

Rice. Organ of Corti

Hair cells have hairs that rise above the surface and reach the integumentary membrane (tectorial membrane). The latter extends from the edge of the spiral bone plate and hangs over the organ of Corti.

When sound stimulation of the inner ear occurs, vibrations occur in the main membrane on which the hair cells are located. Such vibrations cause stretching and compression of the hairs against the integumentary membrane, and generate a nerve impulse in the sensory neurons of the spiral ganglion.

Rice. Hair cells

WIRING DEPARTMENT

The nerve impulse from the hair cells spreads to the spiral ganglion.

Then by auditory ( vestibulocochlear) nerve the impulse enters the medulla oblongata.

In the pons, some of the nerve fibers pass through the decussation (chiasm) to the opposite side and go to the quadrigeminal region of the midbrain.

Nerve impulses through the nuclei of the diencephalon are transmitted to the auditory zone of the temporal lobe of the cerebral cortex.

The primary auditory centers serve for the perception of auditory sensations, the secondary ones for their processing (understanding speech and sounds, perceiving music).

Rice. Hearing analyzer

The facial nerve passes along with the auditory nerve into the inner ear and under the mucous membrane of the middle ear follows to the base of the skull. It can be easily damaged by inflammation of the middle ear or trauma to the skull, so hearing and balance disorders are often accompanied by paralysis of the facial muscles.

Physiology of hearing

The hearing function of the ear is provided by two mechanisms:

• sound conduction: conduction of sounds through the outer and middle ear to the inner ear;
• sound perception: perception of sounds by receptors of the organ of Corti.

SOUND CONDUCTION

The outer and middle ear and the perilymph of the inner ear belong to the sound-conducting apparatus, and the inner ear, that is, the spiral organ and leading nerve pathways, belong to the sound-receiving apparatus. The auricle, due to its shape, concentrates sound energy and directs it towards the external auditory canal, which conducts sound vibrations to the eardrum.

Having reached the eardrum, sound waves cause it to vibrate. These vibrations of the eardrum are transmitted to the malleus, through the joint to the incus, through the joint to the stapes, which closes the window of the vestibule (oval window). Depending on the phase of the sound vibrations, the base of the stapes is either squeezed into the labyrinth or pulled out of it. These movements of the stapes cause vibrations in the perilymph (see figure), which are transmitted to the main membrane of the cochlea and to the organ of Corti located on it.

As a result of vibrations of the main membrane, the hair cells of the spiral organ touch the integumentary (tentorial) membrane overhanging them. In this case, stretching or contraction of the hairs occurs, which is the main mechanism for converting the energy of mechanical vibrations into the physiological process of nervous excitation.

The nerve impulse is transmitted by the endings of the auditory nerve to the nuclei of the medulla oblongata. From here, impulses travel along corresponding leading paths to the auditory centers in the temporal parts of the cerebral cortex. Here the nervous excitement turns into a sensation of sound.

Rice. Sound path: auricle - external auditory canal - tympanic membrane - malleus - incus - pedicle - oval window - vestibule of the inner ear - scala vestibule - basement membrane - hair cells of the organ of Corti. Path of the nerve impulse: hair cells of the organ of Corti - spiral ganglion - auditory nerve - medulla oblongata - diencephalon nuclei - temporal lobe of the cerebral cortex.

SOUND PERCEPTION

A person perceives sounds of the external environment with an oscillation frequency from 16 to 20,000 Hz (1 Hz = 1 oscillation per 1 s).

High frequency sounds are perceived bottom curl, and low-frequency sounds at its tip.

Rice. Schematic representation of the main membrane of the cochlea (frequencies distinguishable by different parts of the membrane are indicated)

Ototopics- WithThe ability to locate a sound source in cases where we cannot see it is called. It is associated with the symmetrical function of both ears and is regulated by the activity of the central nervous system. This ability arises because the sound that comes from the side does not enter different ears at the same time: into the ear of the opposite side - with a delay of 0.0006 s, with a different intensity and in a different phase. These differences in the perception of sound by different ears make it possible to determine the direction of the sound source.

Analyzers- This functional systems, providing analysis (discrimination) of stimuli acting on the body, transforming the resulting stimuli into a biologically appropriate response. The following links can be distinguished in their structure:
- peripheral section - sensory organ receptors;
- conduction section - nerve pathways along which excitation is transmitted to the cerebral cortex;
- central section - a section of the cerebral cortex that converts the received irritation into a certain sensation. Modern man has the following analyzers:

Visual analyzer– the most informative channel (80 - 90% of information about the outside world). The perception of light stimuli is carried out using light-sensitive cells, rods and cones, located in the retina of the eye. The disadvantages of the visual channel include the limited field of view (horizontally 120-160 0, vertically 55-70 0). With color perception, the size of the field narrows. The visual analyzer has spectral sensitivity. U modern man visibility falls on the yellow-green component of the spectrum.

Hearing analyzer to the greatest extent complements the information obtained with the help of a visual analyzer, as it has a “all-round view”. Provides the perception of sound vibrations using the sensitive endings of the auditory nerve. Basic parameters of sound signals - level sound pressure and frequency (perceived as loudness and pitch).

Tactile and vibration sensitivity (touch) manifests itself when the skin surface is exposed to various mechanical stimuli (touch, pressure). Provides perception of muscle contraction and relaxation through mechanoreceptors in body tissues.

Temperature sensitivity characteristic of organisms with a constant body temperature. There are two types of thermoreceptors in the skin, some react only to cold, others only to heat. Latent period - 0.25 s

Smell is a type of sensitivity aimed at the perception of odorous substances with the help of olfactory receptors located in the yellow epithelium of the nasal concha.

Taste analyzer ensures the perception of sour, salty, sweet and bitter with the help of chemoreceptors - taste buds located on the tongue, in the mucous membrane of the palate, larynx, pharynx, tonsils.

Main characteristic analyzer is its sensitivity. Not every intensity of the stimulus acting on the analyzer causes a sensation. Experiments have established that the magnitude of sensations changes more slowly than the strength of the stimulus. This empirical psychophysical Weber-Fechner law expressed by dependence: E = K * log (I) + C

Where E is the intensity of sensations, I is the intensity of the stimulus, K and C are constants.

17. Visual analyzer and its capabilities

The visual analyzer provides more than 80% of information about the outside world, is important in ensuring safety, and is characterized by the following indicators:

Visual acuity - the ability to separate objects - is controlled by a large number of biocybernetic devices; there is a system that ensures clarity of the image on the retina by changing the curvature of the lens; in addition, the illumination of the retina is regulated by the diameter of the pupil;

Field of view - consists of the central region of binocular vision, providing stereoscopic perception; its boundaries in individuals depend on anatomical factors (size and shape of the nose, eyelids, orbits, etc.); field of view covers approximately 240° horizontally and 150° vertically in normal natural light; any decrease in illumination, some diseases (glaucoma), defects in blood vessels, lack of oxygen lead to sharp decrease fields of view;

Brightness contrast - sensitivity to it is an important indicator of the visual analyzer; its threshold (the smallest perceived brightness difference) depends on the level of brightness in the field of view and its uniformity; the optimal threshold is recorded in natural light;

Color perception is the ability to distinguish the colors of objects. Color vision is simultaneously a physical, physiological, and psychological phenomenon, which consists in the ability of the eye to respond to radiation of different wavelengths, in the specific perception of these radiations. The perception of color is affected by the wavelength of the radiation, the brightness of the light source, the reflection or transmission of light by the object, and the quality and intensity of the lighting. Color blindness (color blindness) is a genetic abnormality, but color vision can change under the influence of certain medications and chemicals. For example, taking barbiturates (hypnotics and sedatives) causes temporary defects in the yellow-green zone; cocaine increases sensitivity to blue and decreases sensitivity to red; caffeine, coffee, Coca-Cola weaken sensitivity to blue and enhance red color; tobacco causes defects in the red-green zone, especially in the red (defects can be permanent).

18 hearing analyzer and its characteristics.

The auditory analyzer perceives sounds, which are acoustic vibrations that can be perceived by the hearing organ in the range of 16-20,000 Hz.

An important characteristic of hearing is its acuity or auditory sensitivity. It is determined by the minimum value of the sound stimulus that causes an auditory sensation. Hearing acuity depends on the frequency of the perceived sound signal. The absolute threshold of hearing is the minimum intensity of sound pressure that causes an auditory sensation.

As the sound intensity increases, the appearance of unpleasant sensation, and then ear pain. The lowest sound pressure level at which pain occurs is called the threshold of auditory discomfort. It is on average 80-100 dB relative absolute threshold audibility. The intensity of the sound influence determines the volume of the sensation, frequency - its height. An essential characteristic of hearing is the ability to differentiate sounds of different intensities by the sensation of their loudness. The minimum value of the perceived difference in sound intensity is called the differential threshold for the perception of sound intensity. Normally, for the middle part of the frequency range of sound waves, this value is about 0.7-1.0 dB. Since hearing is a means of communication between people, the ability to perceive speech or speech hearing is of particular importance in its assessment. Particularly important in assessing hearing is the comparison of indicators of speech and tonal hearing, which gives an idea of ​​the state of various parts of the auditory analyzer (audiometry). The function of spatial hearing is important, which is to determine the position and movement of a sound source in space.

Odor and taste analyzers

Smell- the ability to perceive odors - is carried out thanks to the olfactory analyzer, the receptors of which are sensory nerve cells located in the nasal mucosa.

These cells convert the energy of the stimulus into nervous stimulation and transmit it to the olfactory center of the brain. This requires direct contact of the receptor with the odorant molecule. These molecules, deposited on small area membranes of the olfactory receptor cause a local change in its permeability to individual ions. As a result, receptor potential develops - the initial stage of nervous excitation. A person has different sensitivity to odorous substances, and to some substances it is especially high. For example, ethyl mercaptan is felt when it is present in an amount equal to 0.00019 mg per 1 liter of air. The total range of perceived concentrations can span 12 orders of magnitude.

Visual analyzer. The peripheral part of the visual analyzer is photoreceptors located on the retina of the eye. Nerve impulses along the optic nerve (conducting section) enter the occipital region - the brain section of the analyzer. In the neurons of the occipital region of the cerebral cortex, diverse and varied visual sensations arise.

The eye consists of the eyeball and ancillary apparatus. The wall of the eyeball is formed by three membranes: the cornea, the sclera, or albuginea, and the choroid. The inner (choroid) layer consists of the retina, on which photoreceptors (rods and cones) are located, and its blood vessels.

The eye consists of a receptor apparatus located in the retina and an optical system. The optical system of the eye is represented by the anterior and posterior surfaces of the cornea, lens and vitreous body. To see an object clearly, it is necessary that rays from all its points fall on the retina. The adaptation of the eye to clearly seeing objects at different distances is called accommodation. Accommodation is carried out by changing the curvature of the lens. Refraction is the refraction of light in the optical media of the eye.

There are two main anomalies in the refraction of rays in the eye: farsightedness and myopia.

Field of view is the angular space visible to the eye with a fixed gaze and a motionless head.

The retina contains photoreceptors: rods (with the pigment rhodopsin) and cones (with the pigment iodopsin). Cones provide daytime vision and color perception, rods provide twilight and night vision.

A person has the ability to distinguish a large number of colors. The mechanism of color perception, according to the generally accepted, but already outdated three-component theory, is that the visual system has three sensors that are sensitive to the three primary colors: red, yellow and blue. Therefore, normal color vision is called trichromasia. With a certain mixture of three primary colors, a feeling arises white. If one or two primary color sensors malfunction, correct color mixing is not observed and color perception disturbances occur.

There are congenital and acquired forms of color anomaly. With congenital color anomalies, a decrease in sensitivity to blue color, and if acquired - to green. Dalton's color anomaly (color blindness) is a decrease in sensitivity to shades of red and green. This disease affects about 10% of men and 0.5% of women.

The process of color perception is not limited to the reaction of the retina, but significantly depends on the processing of received signals by the brain.

Hearing analyzer.

The significance of the auditory analyzer is the perception and analysis of sound waves. The peripheral section of the auditory analyzer is represented by the spiral (Corti) organ of the inner ear. The auditory receptors of the spiral organ perceive the physical energy of sound vibrations that come to them from the sound-collecting (outer ear) and sound-transmitting apparatus (middle ear). Nerve impulses generated in the receptors of the spiral organ go through the conduction pathway (auditory nerve) to the temporal region of the cerebral cortex - the brain section of the analyzer. In the brain section of the analyzer, nerve impulses are converted into auditory sensations.

The hearing organ includes the outer, middle and inner ear.

The structure of the outer ear. The external ear includes the pinna and the external auditory canal.

The outer ear is separated from the middle ear by the eardrum. On the inside, the eardrum is connected to the handle of the malleus. The eardrum vibrates with any sound according to its wavelength.

Structure of the middle ear. The middle ear includes a system of auditory ossicles - the hammer, incus, stapes, and auditory (Eustachian) tube. One of the bones - the malleus - is woven with its handle into the tympanic membrane, the other side of the malleus is articulated with the anvil. The incus is connected to the stapes, which is adjacent to the membrane of the fenestra vestibule (oval window) of the inner wall of the middle ear.

The auditory ossicles are involved in transmitting vibrations of the eardrum caused by sound waves to the window of the vestibule, and then to the endolymph of the cochlea of ​​the inner ear.

The fenestra vestibule is located on the wall separating the middle ear from the inner ear. There is also a round window. The oscillations of the endolymph of the cochlea, which began at the oval window, spread along the passages of the cochlea, without damping, to the round window.

Structure of the inner ear. The inner ear (labyrinth) includes the vestibule, semicircular canals and the cochlea, which contains special receptors that respond to sound waves. The vestibule and semicircular canals do not belong to the organ of hearing. They represent the vestibular apparatus, which is involved in regulating the position of the body in space and maintaining balance.

On the main membrane of the middle course of the cochlea there is a sound-receiving apparatus - a spiral organ. It consists of receptor hair cells, the vibrations of which are converted into nerve impulses that spread along the fibers of the auditory nerve and enter the temporal lobe of the cerebral cortex. Neurons in the temporal lobe of the cerebral cortex become excited, and a sensation of sound arises. This is how air conducts sound.

With air conduction of sound, a person is able to perceive sounds in a very wide range - from 16 to 20,000 vibrations per 1 s.

Bone conduction of sound occurs through the bones of the skull. Sound vibrations are well conducted by the bones of the skull, transmitted directly to the perilymph of the upper and lower courses of the cochlea of ​​the inner ear, and then to the endolymph of the middle course. The main membrane with hair cells vibrates, as a result of which they are excited, and the resulting nerve impulses are subsequently transmitted to the neurons of the brain.

Air conduction of sound is better expressed than bone conduction.

Gustatory and olfactory analyzers.

The significance of a taste analyzer is to test food in direct contact with the oral mucosa.

Taste buds (peripheral section) are embedded in the epithelium of the oral mucosa. Nerve impulses along the conduction pathway, mainly the vagus, facial and glossopharyngeal nerves, enter the brain end of the analyzer, located in the immediate vicinity of the cortical section of the olfactory analyzer.

Taste buds (receptors) are concentrated mainly on the papillae of the tongue. The majority of taste buds are found on the tip, edges and back of the tongue. Taste receptors are also located on back wall pharynx, soft palate, tonsils, epiglottis.

Irritation of some papillae causes a sensation of only sweet taste, others - only bitter, etc. At the same time, there are papillae, the stimulation of which is accompanied by two or three taste sensations.

The olfactory analyzer takes part in determining odors associated with the appearance of environment odorous substances.

The peripheral section of the analyzer is formed by olfactory receptors, which are located in the mucous membrane of the nasal cavity. From the olfactory receptors, nerve impulses travel through the conductor section - the olfactory nerve - to the brain section of the analyzer - the area of ​​the hook and hippocampus of the limbic system. Various olfactory sensations arise in the cortical part of the analyzer.

Olfactory receptors are concentrated in the area of ​​the upper nasal passages. There are cilia on the surface of the olfactory cells. This increases the possibility of their contact with molecules of odorous substances. Olfactory receptors are very sensitive. Thus, to obtain the sensation of smell, it is enough for 40 receptor cells to be excited, and only one molecule of the odorous substance must act on each of them.

The sensation of smell at the same concentration of an odorous substance in the air occurs only at the first moment of its action on the olfactory cells. Subsequently, the sensation of smell weakens. The amount of mucus in the nasal cavity also affects the excitability of the olfactory receptors. With increased mucus secretion, for example during a runny nose, the sensitivity of the olfactory receptors to odorous substances decreases.

Tactile and temperature analyzers.

The activity of the tactile analyzer is associated with distinguishing various effects on the skin - touch, pressure.

Tactile receptors located on the surface of the skin and mucous membranes of the mouth and nose form the peripheral section of the analyzer. They become aroused when touched or pressed. The conductive section of the tactile analyzer is represented by sensitive nerve fibers coming from receptors in the spinal cord (through the dorsal roots and dorsal columns), medulla oblongata, visual thalamus and neurons of the reticular formation. The brain section of the analyzer is the posterior central gyrus. Tactile sensations arise in it.

Tactile receptors include tactile corpuscles (Meissner's), located in the vessels of the skin, and tactile menisci (Merkel's discs), which are found in large numbers on the tips of the fingers and lips. Pressure receptors include lamellar corpuscles (Pacini), which are concentrated in the deep layers of the skin, tendons, ligaments, peritoneum, and intestinal mesentery.

Temperature analyzer. Its significance is to determine the temperature of the external and internal environment of the body.

The peripheral section of this analyzer is formed by thermoreceptors. Changing the temperature of the internal environment of the body leads to excitation of temperature receptors located in the hypothalamus. The conductive section of the analyzer is represented by the spinothalamic tract, the fibers of which end in the nuclei of the visual thalamus and neurons of the reticular formation of the brain stem. The brain end of the analyzer is the posterior central gyrus of the CGM, where temperature sensations are formed.

Thermal receptors are represented by Ruffini corpuscles, cold receptors - by Krause flasks.

Thermoreceptors in the skin are located at different depths: cold receptors are more superficial, and heat receptors are deeper.

INTERNAL ANALYZERS

Vestibular analyzer. Participates in the regulation of the position and movement of the body in space, in maintaining balance, and is also related to the regulation of muscle tone.

The peripheral section of the analyzer is represented by receptors located in the vestibular apparatus. They are excited by changes in the speed of rotational motion, linear acceleration, changes in the direction of gravity, and vibration. The conduction pathway is the vestibular nerve. The brain section of the analyzer is located in the anterior parts of the temporal lobe of the CGM. As a result of excitation of the neurons of this part of the cortex, sensations arise that give ideas about the position of the body and its individual parts in space, helping to maintain balance and maintain a certain body posture at rest and during movement.

The vestibular apparatus consists of the vestibule and three semicircular canals of the inner ear. Semicircular canals are narrow passages of regular shape, which are located in three mutually perpendicular planes. The upper, or anterior, canal lies in the frontal plane, the posterior canal lies in the sagittal plane, and the outer canals lie in the horizontal plane. One end of each channel is flask-shaped and is called an ampulla.

Excitation of receptor cells occurs due to the movement of endolymph channels.

An increase in the activity of the vestibular analyzer occurs under the influence of changes in the speed of body movement.

Motor analyzer. Due to the activity of the motor analyzer, the position of the body or its individual parts in space and the degree of contraction of each muscle are determined.

The peripheral section of the motor analyzer is represented by proprioceptors located in muscles, tendons, ligaments and periarticular bursae. The conduction section consists of the corresponding sensory nerves and pathways of the spinal cord and brain. The brain section of the analyzer is located in the motor area of ​​the cerebral cortex - the anterior central gyrus of the frontal lobe.

Proprioceptors are: muscle spindles, located among muscle fibers, bulbous bodies (Golgi), located in tendons, lamellar bodies, found in the fascia covering the muscles, in tendons, ligaments and periosteum. Changes in the activity of various proprioceptors occur at the moment of muscle contraction or relaxation. Muscle spindles are always in a state of some excitement. Therefore, nerve impulses are constantly sent from muscle spindles to the central nervous system, to the spinal cord. This leads to the fact that motor nerve cells - motor neurons of the spinal cord are in a state of tone and continuously send rare nerve impulses along the efferent pathways to the muscle fibers, ensuring their moderate contraction - tone.

Interoceptive analyzer. This analyzer of internal organs is involved in maintaining the constancy of the internal environment of the body (homeostasis).

The peripheral section is formed by a variety of interoreceptors, diffusely located in the internal organs. They are called visceroreceptors.

The conduction section includes several nerves of different functional significance that innervate the internal organs, the vagus, the splanchnic and the visceral pelvic. The brain section is located in the motor and premotor areas of the CGM. Unlike external analyzers, the brain section of the interoceptive analyzer has significantly fewer afferent neurons that receive nerve impulses from receptors. Therefore, a healthy person does not feel the work of internal organs. This is due to the fact that afferent impulses coming from interoceptors to the brain section of the analyzer are not converted into sensations, that is, they do not reach the threshold of our consciousness. However, upon stimulation of some visceroreceptors, for example, receptors Bladder and rectum, if their walls are stretched, there is a feeling of urge to urinate and defecate.

Visceroceptors are involved in regulating the functioning of internal organs and carry out reflex interactions between them.

Pain is a physiological phenomenon that informs us about harmful effects that damage or pose a potential danger to the body. Painful irritations can occur in the skin, deep tissues and internal organs. These stimuli are perceived by nociceptors located throughout the body, with the exception of the brain. The term nociception refers to the process of sensing damage.

When, upon irritation of cutaneous nociceptors, nociceptors of deep tissues or internal organs of the body, the resulting impulses, following classical anatomical pathways, reach the higher parts of the nervous system and are reflected by consciousness, a sensation of pain is formed. The complex of the nociceptive system is equally balanced in the body by the complex of the antinociceptive system, which provides control over the activity of the structures involved in the perception, conduction and analysis of pain signals. The antinociceptive system reduces pain sensations inside the body. It has now been established that pain signals coming from the periphery stimulate the activity of various parts of the central nervous system (periductal gray matter, raphe nuclei of the brainstem, nucleus of the reticular formation, nucleus of the thalamus, internal capsule, cerebellum, interneurons of the dorsal horns of the spinal cord, etc. ) have a descending inhibitory effect on the transmission of nociceptive afferentation in the dorsal horns of the spinal cord.

In the mechanisms of development of analgesia, the greatest importance is attached to the serotonergic, noradrenergic, GABAergic and opioidergic systems of the brain. The main one, the opioidergic system, is formed by neurons, the body and processes of which contain opioid peptides (beta-endorphin, met-enkephalin, leu-enkephalin, dynorphin). By binding to certain groups of specific opioid receptors, 90% of which are located in the dorsal horns of the spinal cord, they promote the release of various chemicals (gamma-aminobutyric acid) that inhibit the transmission of pain impulses. This natural, natural pain-relieving system is as important to normal functioning as the pain signaling system. Thanks to it, minor injuries such as a bruised finger or sprained ligaments cause severe pain only for a short time - from a few minutes to several hours, without causing us to suffer for days and weeks, which would happen if the pain persisted until complete healing.

Lecture No. 4

Subject:Physiological characteristics of a person.

Lecture outline:

General characteristics of analyzers. Functional diagram and

basic parameters of analyzers.

Characteristics of the visual analyzer.

Characteristics of the auditory analyzer.

Characteristics of the skin analyzer.

Kinesthetic analyzer.

Olfactory analyzer.

Alekseev S.V., Usenko V.R. Occupational hygiene. – M.: Medicine, 1998. – 244 p.

Life safety: A textbook for secondary special education students. Textbook establishments / S.V. Belov, V.A. Devisilov, A.F. Kozyakov and others / edited by. ed. S.V. Belova. – M.: Higher. school, 2003. – 357 p.

Life safety. Ed. prof. E. A. Arustamova. M.: “Dashkov and Co.,” 2003. -258 p.

Belyakov G.I. Workshop on labor protection. – M.: Kolos, 1999. – 192 p.

Hwang T.A., Hwang P.A. Life safety. Series "Textbooks and teaching aids". Rostov n/d: “Phoenix”, 2001. – 352 p.

6. Chusov Yu.N. Human physiology. – M.: Education, 1981. – 193 p.

1. General characteristics of analyzers. Functional diagram and main parameters of analyzers.

Expedient and safe human activity is based on the constant receipt and analysis of information about the external environment and about one’s internal state for a timely adaptive response. All irritations acting on the body from the outside and arising within it are perceived by a person with the help of sensory organs, including the organs of vision, hearing, gravity, smell, taste, and touch. Analyzers receive information from the senses about the state and changes in the external and internal environment and process it.

Analyzers – functional sensory systems that provide qualitative and quantitative analysis of stimuli affecting the body. The structure of each analyzer can be divided into three sections:

peripheral section – receptors, most often located in the sensory organs, perceiving irritations and converting them into nerve impulses;

conductor department – nerve pathways along which nerve impulses are transmitted to the cerebral cortex;

central department (nerve centers) are sensitive areas in the cerebral cortex that transform the received irritation into a certain sensation.

The main characteristic of analyzers is sensitivity – the property of a living organism to perceive irritations caused by the action of stimuli from the external or internal environment. Sensitivity is characterized by the value threshold of sensation . There are absolute and differential sensation thresholds.

Absolute threshold of sensation - this is the minimum force of irritation at which a sensation occurs.

Differential (difference) sensation threshold - this is the minimum amount by which the stimulus must be increased in order to obtain a minimal change in sensation.

Each analyzer is characterized by the minimum duration of exposure to the stimulus required for the occurrence of sensation. The time from the onset of exposure to the appearance of sensation is called latent period . Its value for various analyzers ranges from 0.09 to 1.6 s.

In a simplified form, the analyzer circuits are presented in Table 1.

2. Characteristics of the visual analyzer.

A person receives more than 80% of all information about the external environment thanks to lighting through the visual analyzer. Under the influence of a flow of radiant energy, light and color sensations arise, the level of which depends on the brightness and illumination of the objects in question, objects, and surrounding surfaces.

Visual analyzer , like any other analyzer, consists of three functional parts. The peripheral part in the visual analyzer is the most important of the sense organs - the organ of vision - eye .

Eye consists of an almost spherical eyeball, extraocular muscles, eyelids, and lacrimal apparatus (Fig. 1).



Rice. 1. Diagram of the structure of the human eye: 1 – fibrous membrane; 2 – cornea; 3 pupil; 4 – iris; 5 – lens; 6 – ciliary muscle; 7 – vitreous body; 8 – retina; 9 – optic nerve; 10 – choroid; 11 – yellow spot; 12 – central fossa

Light enters the eye through the transparent part of the fibrous membrane 1 – cornea 2, pupil 3 – hole of variable size in the center of the iris 4; then the light passes through lens 5, having the shape of a biconvex lens, vitreous 7 and then reaches light-sensitive photoreceptor cells retina 8. Ciliary muscle 6 regulates the curvature of the surface of the lens, ensuring the ability of the eye to accommodate.

Accommodation – adaptation to clear vision of objects located at different distances from the eye. In the figure, the lower part of the crunch-face is shown at rest, the upper part - during accommodation . Accommodation involves two processes, each of which will be discussed separately.

Reflex change in pupil diameter . When the lighting intensity changes, the reflex contraction of the annular and radial muscles of the eye changes the diameter (lumen) of the pupil. Thanks to this, the pupil has the ability to regulate the amount of light entering the retina, preventing it from being damaged. The brighter the light, the narrower the pupil, the less light hits the retina, and vice versa. When the brightness decreases, the pupil enlarges. The maximum pupil sizes of 2 and 8 mm can be observed on a sunny day and a dark night, respectively.

Eye sensitivity unstable towards the light. It depends on the degree of illumination. It is known that if you move from a brightly lit room to a dark room, then at the initial moment the eyes do not distinguish anything. Gradually, the sensitivity of the eye increases, as the intensity of the decay of light-sensitive substances decreases and the ability of the eye to distinguish objects is restored. After a long stay in the dark (about 1 hour), the sensitivity of the eye becomes maximum. If you now go out into the light, then at the first moment the eyes also stop seeing anything: the restoration of light-sensitive substances lags behind their very intensive decay. After 1–2 minutes, the sensitivity of the eye decreases and vision is restored. The ability of the eye to adapt to the level of illumination, changing its sensitivity, is called adaptation.

The main physiological indicators of the visual analyzer are contrast sensitivity, visual acuity, field of vision, speed of discrimination, stability of clear vision, color discrimination.

Contrast sensitivity – the ability of the visual analyzer to distinguish an object against the background of others. To assess the functional state of the visual analyzer, an indicator called the contrast sensitivity threshold is used.

Contrast sensitivity threshold – the smallest perceived difference in brightness of the object in question and the background (the surface adjacent to the object).

Visual acuity - this is the ability to separate perception of two points or objects. With normal visual acuity, a person can distinguish an object with angular size 1 min (minimum viewing angle).

Discrimination speed – the ability of the visual analyzer to distinguish the details of objects in a minimum observation time.

line of sight consists of a central region of binocular vision, providing stereoscopic perception. The boundaries of the field of view depend on anatomical factors: the size and shape of the nose, eyelids, orbits, etc. Horizontally, the field of view covers 120 - 180°, vertically up - 55 - 60° and down - 65 - 72°.

Persistence of Clear Vision – the ability of the visual analyzer to clearly distinguish an object within a given time. The longer the period of clear vision, the higher the performance of the visual analyzer.

Color perception (color vision) – the ability of the visual analyzer to distinguish the colors of objects. The appearance of one or another color sensation: from violet to red colors depends on the wavelength of visible radiation. Color vision impairment – color blindness (color blindness) is a genetic abnormality.

3. Characteristics of the auditory analyzer.

Hearing analyzer includes the ear, nerves and auditory centers located in the cerebral cortex

Human ear is an organ of hearing in which the peripheral part of the auditory analyzer is located, containing mechanoreceptors that are sensitive to sounds, to gravity and to movement in space. Most ear structures designed to perceive, amplify and convert sound energy into electrical impulses, which, when entering the auditory areas of the brain, cause an auditory sensation.

The human hearing organ (Fig. 2) includes the outer, middle and inner ear. The outer ear consists of auricle 1, which captures and directs sound waves to the outside ear canal 2. The auditory canal is quite wide, but approximately in the middle it narrows significantly. This circumstance should be kept in mind when removing a foreign body from the ear. The skin of the ear canal is covered with fine hairs. The gland ducts that produce earwax open into the lumen of the passage. Hairs and earwax perform protective function – protect the ear canal from the penetration of dust, insects, and microorganisms.

Behind the ear canal, at its border with the middle ear, there is a thin elastic eardrum 3. Behind it is the cavity of the middle ear 4. Inside this cavity there are three auditory ossicles - the hammer 6, the incus 7 and the stirrup 8. The cavity of the middle ear communicates with the oral cavity through Eustachian (auditory) tube 5. The Eustachian tube serves to equalize the pressure in the middle ear cavity with the outer ear. If a pressure difference occurs, hearing acuity is impaired, and if the pressure difference is very large, the eardrum may rupture. To prevent this from happening, you need to open your mouth and make several swallowing movements.

Located in the inner ear spiral-shaped snail 9. Inside, in one of the canals of the cochlea, filled with liquid, there is a main membrane on which the sound-receiving apparatus is located - organ of corti . It consists of 3–4 rows of receptor cells, total number which reaches 24,000.



Rice. 2. Human hearing organ: a – external ear; b – middle ear; c – inner ear; 1 – auricle; 2 – external auditory canal; 3 – eardrum; 4 – middle ear cavity; 5 – Eustachian tube; 6 – hammer; 7 – anvil; 8 – stirrup; 9 – snail; 10 – vestibular apparatus; 11 – vestibule; 12 – semicircular canals; 13 – auditory nerve; 14 – nerve of the vestibule.

Sound waves captured by the auricle cause vibrations in the eardrum and are then transmitted through the system of auditory ossicles and fluid vibrations arising in the cochlea to the receiving phono-receptor cells organ of corti , causing them irritation. Auditory stimulation, converted into nervous excitement (nerve impulse), travels along auditory nerve 13 to the cerebral cortex, where higher analysis of sounds occurs - auditory sensations arise.

One of the main characteristics of hearing is the perception of sounds certain frequency range . The human ear is capable of hearing sounds with frequencies ranging from 16 to 20,000 Hz.

An important characteristic of hearing is hearing acuity or hearing sensitivity . Hearing sensitivity can be assessed by the absolute threshold sound pressure (Pa) that produces auditory sensation. The minimum sound pressure that can be perceived by the human ear is called hearing threshold . The threshold of hearing depends on the frequency of the sound. In practice, for the convenience of assessing the perception of sounds, it is customary to use a relative value: sound pressure level, measured in decibels (dB). The hearing threshold at a frequency of 1000 Hz, accepted as the standard reference frequency in acoustics, approximately corresponds to the sensitivity threshold of the human ear and is equal to 0 dB.

At high sound pressure levels (120 - 130 dB), an unpleasant sensation and then pain in the hearing organs may appear. The lowest sound pressure at which pain occurs is called pain threshold . In the range of audible frequencies, this threshold is on average 80–100 dB higher than the hearing threshold.

An essential characteristic of hearing is the ability to differentiate sounds of different intensities by the sensation of their volume. The minimum amount of perceived difference in sound intensity is called differential perception threshold sound strength. For sounds in the middle part of the sound spectrum, this value is about 0.7 - 1.0 dB.

Since hearing is a means of communication between people, the ability to perceive speech or speech hearing is of particular importance in its assessment. It is especially important in assessing hearing to compare the indicators of speech and tonal hearing, which gives an idea of ​​​​the state of various parts of the auditory analyzer. Of great importance is the function of spatial hearing, which consists in determining the position and movement of a sound source.

4. Characteristics of the skin analyzer.

One of the most important functions skin is a receptor function. The skin contains a huge number of receptors that perceive various external irritations: pain, heat, cold, touch. On 1 cm 2 of skin there are approximately 200 pain, 20 cold, 5 heat and 25 pressure receptors, which represent the peripheral part of the skin analyzer.

Painful sensations cause defensive reflexes, in particular the reflex of moving away from the stimulus. Pain sensitivity, being a signal, mobilizes the body to fight for self-preservation. Under the influence of a pain signal, the work of all body systems is restructured and its reactivity increases.

Mechanical effects on the skin that do not cause pain are perceived tactile analyzer . Tactile sensitivity is an integral part of the sense of touch. The sensitivity of the skin of different parts of the body to the effects of tactile stimuli is different, i.e. they have different thresholds of tactile sensitivity, for example, the minimum threshold of sensation for the fingertips of the hands is 3 mg/mm2, back side brushes – 12 mg/mm2, for skin in the heel area – 250 mg/mm2.

Tactile sensitivity Together with other types of skin sensitivity, it can to some extent compensate for the absence or insufficiency of the function of other senses.

Temperature sensitivity of the skin is provided by cold thermoreceptors with a maximum temperature perception of 25–30 °C and thermal ones with a maximum perception of 40 °C.

The highest density of thermoreceptors is in the skin of the face, there are fewer of them in the skin of the torso, and even less in the skin of the extremities. By transmitting information about changes in ambient temperature, thermoreceptors play a critical role in thermoregulation processes that ensure constant body temperature.

5. Kinesthetic analyzer.

Motor or kinesthetic analyzer is a physiological system that transmits and processes information from the receptors of the musculoskeletal system, and also participates in the organization and implementation of coordinated movements. Physical activity contributes to the adaptation of the human body to changes in the environment (climate, time zones, working conditions, etc.).

Various types of movements are characterized by the dynamics of physiological processes, which, when optimized, ensure the best preservation of the body’s vital functions.

Excessive mobilization functional activity that is not provided with the necessary level of coordination and activity of recovery processes during work and for a long time after its completion is characterized as hyperdynamia . This condition occurs with excessive sports or heavy physical labor, or with prolonged emotional stress. Hyperdynamia develops as a result of mobilization of the functions of the neuromuscular, cardiovascular, respiratory and other systems that is inadequate for the functional state of the body and can be accompanied by a number of painful symptoms.

Low physical activity is the cause physical inactivity . This condition is characterized by a decrease in the activity of all organs, systems and a disorder of interconnection in the body, metabolism is disrupted, the reliability and stability of the human body decreases under significant functional loads and the influence of unfavorable environmental factors.

Thus, all this allows us to talk about a person’s motor activity as a process that largely contributes to the preservation of his health and work activity.

6. Olfactory analyzer.

The type of sensitivity aimed at the perception of various odorous substances using an olfactory analyzer is called sense of smell . The sense of smell has great importance in ensuring safety, since people with impaired sense of smell are more likely to be at risk of poisoning. Determined for many odorous substances threshold of perception , i.e. the minimum concentration of a substance that can cause a reaction in the olfactory organ.

The main characteristics of the olfactory organ are:

absolute threshold of perception – the concentration of a substance at which a person perceives the odor, but does not recognize it (even for familiar odors);

threshold recognition – the minimum concentration of a substance at which the odor is not only felt, but also recognized.

The difference between the threshold of perception and the threshold of recognition for most substances is one order of magnitude: 10 – 100 mg/m3.

by their nature called pleasant, unpleasant, bad, vague, disgusting, suffocating, etc.;

by intensity they are divided into weak, moderate, pronounced, strong and very strong;

by irritant effect - non-irritating, slightly irritating, unbearable.

Changes in the sense of smell can occur as follows:

hyposmia – decrease in the acuity of smell, while the threshold for odor perception increases;

anosmia – loss of smell perception;

hyperosmia And oxyosmia – heightened sense of smell, while the threshold for smell perception decreases.

Hyposmia can be complete or partial. Occupational hyposmia can be functional (adaptation to smell, fatigue of the olfactory organs), toxic (after inhalation of lead, mercury, chlorine, etc.), respiratory (after inhalation of dust), inflammatory, post-infectious, post-traumatic. Changes in the sense of smell can be of either peripheral or central origin, depending on which part of the olfactory analyzer is damaged.

7. Taste analyzer.

Taste - a sensation that occurs when stimuli act on specific receptors located in different parts of the tongue.

Taste sensation consists of the perception of sour, salty, sweet and bitter; variations in taste result from a combination of the basic sensations listed. Different parts of the tongue have unequal sensitivity to taste substances: the tip of the tongue is more sensitive to sweet , edges of tongue - to sour , tip and edges - to salty and the root of the tongue is most sensitive to bitter .

The mechanism of perception of flavoring substances is associated with specific chemical reactions at the border " substance - taste bud " It is assumed that each receptor contains highly sensitive protein substances that disintegrate when exposed to certain flavoring substances. Excitation from taste buds is transmitted to the central nervous system along specific pathways.

Human analyzers, which are a subsystem of the central nervous system (CNS), are responsible for the perception and analysis of external stimuli. Signals are perceived by receptors - the peripheral part of the analyzer, and processed by the brain - the central part.

Departments

The analyzer is a collection of neurons, which is often called the sensory system. Any analyzer has three sections:

• peripheral - sensitive nerve endings (receptors), which are part of the sense organs (vision, hearing, taste, touch);
• conductive - nerve fibers, a chain of different types of neurons that conduct a signal (nerve impulse) from the receptor to the central nervous system;
• central - an area of ​​the cerebral cortex that analyzes and converts the signal into sensation.



Rice. 1. Analyzer departments.

Each specific analyzer corresponds to a specific area of ​​the cerebral cortex, which is called the cortical nucleus of the analyzer.

Kinds

Receptors, and accordingly analyzers, can be two types:

• external (exteroceptors) - located near or on the surface of the body and perceive environmental stimuli (light, heat, humidity);
• internal (interoceptors) - are located in the walls of internal organs and perceive irritants from the internal environment.



Rice. 2. Location of perception centers in the brain.

Six types of external perception are described in the table “Human Analyzers”.

Analyzer	Receptors	Pathways	Central departments
Visual	Retinal photoreceptors	Optic nerve	Occipital lobe of the cerebral cortex
Auditory	Hair cells of the spiral (or Corti) organ of the cochlea	Auditory nerve	Superior gyrus of the temporal lobe
Flavoring	Tongue receptors	Glossopharyngeal nerve	Anterior temporal lobe
Tactile	Receptor cells: - on bare skin - Meissner corpuscles, located in the papillary layer of the skin; On the hair surface there are hair follicle receptors; Vibrations - Pacinian corpuscles	Musculoskeletal nerves, back, medulla oblongata, diencephalon
Olfactory	Receptors of the nasal cavity	Olfactory nerve	Anterior temporal lobe
Temperature	Heat (Ruffini corpuscles) and cold (Krause flasks) receptors	Myelinated (cold) and unmyelinated (warm) fibers	Posterior central gyrus of the parietal lobe



Rice. 3. Location of receptors in the skin.

Internal ones include pressure receptors, the vestibular apparatus, kinesthetic or motor analyzers.

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Monomodal receptors perceive one type of irritation, bimodal - two types, polymodal - several types. For example, monomodal photoreceptors perceive only light, tactile bimodal ones perceive pain and heat. The vast majority of pain receptors (nociceptors) are polymodal.

Characteristics

Analyzers, regardless of type, have a number of common properties:

• high sensitivity to stimuli, limited by the threshold intensity of perception (the lower the threshold, the higher the sensitivity);
• difference (differentiation) of sensitivity, allowing one to distinguish stimuli by intensity;
• adaptation, which allows you to adjust the level of sensitivity to strong stimuli;
• training, manifested both in a decrease in sensitivity and in its increase;
• preservation of perception after the cessation of the stimulus;
• interaction of different analyzers with each other, allowing you to perceive the completeness of the outside world.

An example of a peculiarity of the analyzer's operation is the smell of paint. People with a low threshold for sensitivity to odors will smell more strongly and react actively (lacrimation, nausea) than people with a high threshold. Analyzers will perceive a strong odor more intensely than other surrounding odors. Over time, the smell will not be noticeable, because... adaptation will occur. If you constantly stay in a room with paint, the sensitivity will become dull. However, upon leaving the premises Fresh air, the smell of paint will be felt and “imagined” for some time.