External analyzers

Reception and analysis of information is carried out using analyzers. The central part of the analyzer is a certain zone in the cerebral cortex. The peripheral part is the receptors that are located on the surface of the body to receive external information, or in the internal organs.

external signals ® receptor® nerve connections® brain

Depending on the specifics of the received signals, there are: external (visual, auditory, pain, temperature, olfactory, gustatory) and internal (vestibular, pressure, kinesthetic) analyzers.

The main characteristic of analyzers is sensitivity.

Lower absolute threshold sensitivity - the minimum value of the stimulus to which the analyzer begins to respond.

If the stimulus causes pain or disruption of the analyzer, this will be the upper absolute threshold of sensitivity. The interval from minimum to maximum determines the sensitivity range (for example, for sound from 20 Hz to 20 kHz).

A person receives 85-90% of all information about the external environment through the visual analyzer. Reception and analysis of information is carried out in the range (light) - 360-760 electromagnetic waves. The eye can distinguish 7 primary colors and more than a hundred shades. The eye is sensitive to the visible range of the electromagnetic wave spectrum from 0.38 to 0.77 microns. Within these limits, different wavelengths produce different sensations (colors) when applied to the retina:

0.38 - 0.455 µm - purple;

0.455 - 0.47 µm - blue;

0.47 - 0.5 microns - blue color;

0.5 - 0.55 µm - green;

0.55 - 0.59 microns - yellow;

0.59 - 0.61 µm - orange;

0.61 - 0.77 microns - red color.

The highest sensitivity is achieved at a wavelength of 0.55 µm

The minimum intensity of light exposure that causes sensation. adaptation of the visual analyzer. Temporal characteristics of signal perception include: latent period - time from the signal being given until the sensation occurs 0.15-0.22 s; the signal detection threshold at higher brightness is 0.001 s, with a flash duration of 0.1 s; incomplete dark adaptation - from several seconds to several minutes.

With the help of sound signals, a person receives up to 10% of information. Auditory signals are used to focus a person’s attention, to transmit information, and to relieve the visual system. The features of the hearing analyzer are:

The ability to be ready to receive information at any time;

The ability to perceive sounds in a wide range of frequencies and highlight the necessary ones;

The ability to accurately determine the location of a sound source.

The perceptive part of the auditory analyzer is the ear, which is divided into three sections: external, middle and internal. Sound waves, penetrating the external auditory canal, vibrate the eardrum and are transmitted through the chain of auditory ossicles into the cochlear cavity of the inner ear. Fluid vibrations in the canal move the fibers of the main membrane in resonance with the sounds entering the ear. Vibrations of the cochlear fibers set the cells of the organ of Corti located in them in motion, a nerve impulse arises, which is transmitted to the corresponding parts of the cerebral cortex. The pain threshold is 130 - 140 dB.

The skin analyzer provides the perception of touch, pain, heat, cold, vibration. One of the main functions of the skin is protective (from mechanical, chemical damage, pathogenic microorganisms, etc.). An important function of the skin is its participation in thermoregulation; 80% of all heat transfer from the body is carried out by the skin. At high temperature external environment, skin vessels dilate (heat output increases), at low temperatures the vessels narrow (heat output decreases). The metabolic function of the skin is to participate in the processes of regulation of general metabolism in the body (water, mineral, carbohydrate). The secretory function is provided by the sebaceous and sweat glands. Endogenous poisons and microbial toxins can be released with sebum.

The olfactory analyzer is designed for human perception of various odors (range of up to 400 items). The receptors are located on the mucous membrane in the nasal cavity. The conditions for the perception of odors are the volatility of the odorous substance and the solubility of the substances. Odors can signal a person about violations of technological processes.

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.

Field of view 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 auditory sensations.

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: level sound pressure, 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), it is possible that unpleasant sensation, and then pain in the hearing organs. 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 loudness. 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. 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. 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 sensory organs.

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 helps the human body adapt to changes 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 value 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 taste substances is associated with specific chemical reactions on 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.

Lecture notes Topic: “General issues of anatomy and physiology of sensory systems. Sensory systems of the body. Types of analyzers. Sense organs."

The student must know:

Ø types of receptors;

Ø structure, functions of the eye;

Ø auxiliary apparatus of the eye;

Ø physiology and visual anomalies;

Ø skin structure, functions;

Ø skin derivatives, functions

Ø The structure of the eye.

From the rubaiyat of Omar Khayyam, the Persian poet-philosopher, he wrote about his contemporaries and time like this: “In this world of fools, scoundrels, hucksters, shut your wise ears, sew your mouth securely, close your eyes.

At least think a little about the safety of your eyes, tongue and ears.”

Guys, please tell me which system Omar Khayyam touched on in his statement. (Sense organs, sensory systems).

Relevance of the topic.

Nowadays this topic is very relevant, since myopia is one of the most common diseases in children. Very important point for developing eyes this school years. Monotonous loads from reading, writing, computer, when the child is forced to concentrating your gaze on close objects, thereby accelerating the process of natural growth of the eyeball and gradually the eye tends to myopia.

In order to prevent these violations and correct them correctly it is necessary to know the anatomy and physiology of the eye.

Target

Ø general principles of anatomy and physiology of the body's sensory systems

Ø types of analyzers.

Ø The concept of analyzers and general properties, types of receptors.

Ø The structure of the eye.

Ø Physiology of vision, visual anomalies.

Ø Skin, auxiliary elements, structure of functions.

1. Analyzer (Greek analysis - decomposition, dismemberment) - these are aggregates of formations,

whose activity ensures the decomposition and analysis in the nervous system of stimuli affecting the body.

Each analyzer consists of three parts:

Peripheral perceiving device containing receptors;

Conducting pathways and centers of the brain;

Higher cortical centers of the brain.

With the help of analyzers, knowledge of the reality around us is carried out, and the information transmitted transmitted to the central nervous system from receptors of internal organs, serves as the basis for self-regulation processes.

The activity of analyzers reflects the external material world. This makes it possible for animals to adapt to environmental conditions, and man, by learning the laws of nature and creating tools, not only adapts, but also actively changes the external environment according to its needs.

All analyzers are divided into two groups: external and internal

To externalhim analyzers include: visual, auditory, gustatory, olfactory and cutaneous (tactile, pain, temperature).

To internal analyzers include: motor, vestibular and visceroceptive.

Motor function(proprioceptive) analyzer is characteristic mainly of skeletal muscles.

Receptors external analyzers are called exteroceptors, internal analyzers - interoreceptors.

Kinteroreceptors include: chemoreceptors, osmoreceptors, volume receptors, proprioceptors receptors, vestibuloreceptors, visceroreceptors, etc.

In addition, all receptors external analyzers are divided into two large groups:

- distantnal receptors(visual - photoreceptors, auditory, olfactory)

- contact receptors (tactile, temperature, taste, pain).

Receptors have a number of common properties.

1. They all have very high excitability.

2. With increasing strength of irritation, the intensity of the sensation increases

3. Almost all receptors have the property of adaptation, i.e. adaptation to the strength of the current stimulus

2. Organ of vision - eye(Latin oculus, Greek ophthalmos) - the most important of the senses. He

is a peripheral receptor part a visual analyzer that provides perception and analysis of light radiation from the environment and generates visual sensations and images. The eye is located in the orbit and consists of the eyeball and ancillary apparatus.

Eyeball has a rounded shape (spherical shape) with a slightly protruding anterior section.

The mass of the eyeball is 7-8 g. The eyeball consists of three membranes and the core (inner core).

Eye shells

1) External - fibrous membrane the densest, fulfills the shielding and light-conducting function. Its anterior smaller part is transparent and is called the cornea. It looks like a watch glass, convex in front and concave in back.

The peripheral edge (limb) of the cornea is inserted into the anterior part of the sclera, into which the cornea passes. The cornea is rich in nerve endings, but does not contain blood vessels. Actively participates in the refraction of light rays. The posterior most part of the fibrous membrane is whitish in color and opaque and is called the sclera. The extraocular muscles are attached to the sclera.

2) Medium - choroid eyeball contains pain a large number of blood vessels provides nutrition to the retina for and release of aqueous humor. It regulates the intensity of the light flux and the curvature of the lens.

In the choroid there are threeparts: anterior - the iris, middle - the ciliary body, posterior - the choroid itself.

The iris is shaped like a disk, in the center which has round hole- pupil. The diameter of the pupil is not constant: the pupil narrows in strong light and expands in the dark, acting as the diaphragm of the eyeball. The iris has two muscles: the sphincter, which constricts the pupil, and the dilator, which causes its expansion. It contains a lot
pigment cells that determine eye color (blue, greenish-gray or brown). Posterior to the iris is the ciliary, or ciliary, body - a circular ridge about 8 mm wide, in the thickness of which there is the ciliary, or accommodative, muscle. The contraction of the ciliary muscle is transmitted through a special ligament of Zinn to the lens, and it changes its curvature. In addition to participating in the accommodation of the eye, the ciliary body produces aqueous humor in the anterior and posterior chambers of the eye and regulates its exchange. The choroid proper, or choroid, makes up most of the choroid and lines the inside of the back of the sclera. It is formed by vessels and connective tissue with pigment cells.

2) Inner (sensitive) membrane of the eyeball - set-chatka (retina) tightly adheres to the choroid. In the retina there are posterior visual Part and a smaller front - “blind” part.
The visual retina consists of an outer pigment part and an inner
nerve part. The most important of them are the photoreceptors of the retina: rods - 130 million. And
cones - 7 million.

Inner core eyes consists of transparent light-refracting Wednesday: vitreous body, lens and aqueous humor filling the eye chambers.

Together these media make up an optical system, b- thanks to which rays of light entering the eyes are focused on the retina: a clear image of objects is obtained on it (in a reduced reverse form). The aqueous humor of the anterior and posterior chambers participates in the nutrition of the cornea and maintains a certain intraocular pressure, which is normally 16-26 mm Hg in humans. The anterior chamber is bounded in front by the cornea, and in the back by the iris and lens, the posterior chamber is bounded in front by the iris, and in the back by the lens, the ciliary band (zinc ligament) and the ciliary body. Through the opening of the pupil, both chambers communicate with each other. The lens is a transparent biconvex lens consisting of epithelial cells and their derivatives - lens fibers. Located between the iris and the vitreous body. In terms of refractive power, it is the second medium (after the cornea) of the optical system of the eye (18 diopters). Consists of a core, cortex and capsule. The ciliary band (ligament of Zinn) is attached to the latter. When the ciliary muscle contracts, the lens increases its curvature; when it relaxes, it flattens. The vitreous body is a clear, jelly-like substance covered by a membrane. Like the lens, it does not contain blood vessels or nerves.

To the auxiliary device eyes include:

1. protective devices: eyebrows, eyelashes, eyelids;

2. lacrimal apparatus, including the lacrimal gland and lacrimal ducts (lacrimal canaliculi, lacrimal sac and nasolacrimal duct);

3. the musculoskeletal system includes 7 muscles: 4 rectus muscles - superior, inferior, lateral and medial; 2 obliques - upper and lower; muscle that lifts the upper eyelid. All of them are striated and contract arbitrarily.

3.Physiology and pathology of vision.

For good vision, you must first of all have a clear image (focusing) of the object in question on the retina. The ability of the eyes to clearly see objects at different distances is called accommodation. tion. It is carried out by changing the curvature of the lens and its refractive power. The mechanism of accommodation of the eye is associated with contraction of the ciliary muscle, which changes the convexity of the lens. The refraction of light in the optical system of the eye is called refraction. Clinical refraction is characterized by the position of the main focus in relation to the retina. If the main focus coincides with the retina, such refraction is called commensurate - emmetropia. If the main focus does not coincide with the retina, then the clinical refraction is disproportionate - ametropia. There are two main refractive errors, which, as a rule, are associated not with insufficiency of the refractive media, but with the abnormal length of the eyeball.

A refractive error in which light rays are focused in front of the retina due to elongation of the eyeball is called myopicbone - myopia(Greek myo - close, close and ops - eye). Distant objects are not clearly visible. To correct myopia, it is necessary to use biconcave lenses.

An anomaly of refraction, in which light rays due to The oscillations of the eyeball are focused behind the retina, called far-nosesightedness - hypermetropia(Greek hypermetros - excessive and ops - eye). To correct farsightedness, biconvex lenses are required. With age, the elasticity of the lens decreases, it hardens and loses its It has the ability to change its curvature when the ciliary muscle contracts. Such senile farsightedness, which develops in people after 40-45 years, is called presbyopia(Greek presbys - old, ops - eye, look). It is corrected with glasses with biconvex lenses, which are worn when reading. Combination in one eye various types refractions or different degrees of one type of refraction is called as-stigmatism(Greek a - negation, stigma - period). With astigmatism, rays coming out from one point of the object are not collected again at one point, and the image turns out blurry. To correct astigma- tism uses converging and diverging cylindrical lenses.

A decrease in the sensitivity of the eye's photoreceptors to light is called adaptation. Adaptation of the eyes when leaving a dark room into bright light (light adaptation) occurs on average in 4-5 minutes. Complete adaptation of the eyes when leaving a light room into a darker one (dark adaptation) takes much longer and occurs on average in 40-50 minutes. The sensitivity of the rods increases by 200,000-400,000 times. That is why radiologists always wear dark glasses when leaving their darkened office into the light. To study the progress of adaptation there are special devices- adaptometers.

The perception of the color of objects is provided by cones. At dusk when only the sticks function, the colors do not differ. There are 7 types of cones that respond to rays of different lengths and cause the sensation of different colors. Not only photoreceptors, but also the central nervous system are involved in color analysis.

4. Leather (cutis), or the outer cover of the body, is an important and functionally multifaceted organ. The skin is not only a shell that delimits internal organs from the external environment, but also by an extensive receptor field that perceives all changes in external and internal environmental factors. This allows us to classify the skin as a sensory organ, i.e. to the peripheral receptor section of the skin analyzer.

In direct contact with external environment, the skin performs the following Features:

1) protects the body from external influences, including mechanical;

2) participates in thermoregulation of the body;

3) releases sweat and sebum (excretory function);

4) contains energy reserves (subcutaneous fat);

5) synthesizes vitamin D to prevent rickets;

6) is an integral and active component of the immune system;

7) participates in water, mineral and other types of metabolism;

8) is a blood depot (about 1 l);

9) perceives numerous irritations from the external environment;

10)reflects the emotional state of a person and, to a certain degree,
penalties affect people's social and sexual relationships.

The skin area of an adult is 1.5-2 m2. Leather thickness in various parts body varies from 0.5 to 5 mm. The weight of the skin reaches 3 kg.

There are 3 layers in the skin:

1) epidermis (periocutum), which develops from the ectoderm;

2) dermis (the skin itself);

3) hypodermis (subcutaneous base - fatty tissue), both developing from mesoderm.

Epidermis- This is the surface layer of the skin. It is represented by stratified squamous keratinizing epithelium. The epidermis is thickest on the palms and soles. Epidermis co- consists of many rows of cells (epidermocytes), which, according to morpho-functional characteristics, are divided into 5 layers: basal, spinous, granular, shiny and horny. Dermis ( the skin itself) is the deep part of the skin consisting of connective tissue. It is divided into 2 layers: papillary and reticular.

Papillary layer adjacent to the epidermis and consists of loose fibrous compounds thread tissue that performs a trophic function. This layer forms numerous projections - papillae, protruding into the epidermis, and determines the individual skin pattern: ridges and grooves on the surface of the epidermis (especially on the palm and sole). This pattern on the distal phalanges of the fingers is unique and is widely used in criminology and forensic medicine to establish identity. The papillae contain loops of blood and lymphatic capillaries and terminal nerve apparatus. In the papillary layer there are bundles of smooth muscle cells associated with the hair follicles (the muscles that lift the hair), and in some places such bundles lie independently: on the skin of the face, neck, dorsum of the hands, and feet. The contraction of these smooth muscle cells causes the appearance of goose bumps. At the same time, blood flow to the skin decreases and heat transfer from the body decreases.

Mesh layer occupies the main part of the dermis and consists of dense, unformed connective tissue. Compact and thick bunches of stakes Lagen and elastic fibers of this layer provide the density, strength and elasticity of the skin. This layer mainly contains sweat, sebaceous glands and hair roots; it also contains bundles of smooth muscles. The reticular layer smoothly, without a sharp border, passes into the subcutaneous base.

Hypodermis(subcutaneous base) - the deepest part of the skin. It consists of interwoven bundles of connective tissue, the loops of which contain fatty accumulations (deposits). The thickness of fat deposits in human skin varies and depends on the type of constitution and fatness. This layer softens the effects of mechanical effects on the skin due to the extensive fat depot of the body.

At the border between the dermis and hypodermis there is a deep (dermal) arterial network, forming a surface at the base of the papillae. papillary (subpapillary) arterial network, and venous plexuses, anastomosing with each other and with the venous plexuses of the papillary layer (blood depot of about 1 liter, participation in thermoregulation). The epidermis is devoid of blood vessels, so it is nourished by the capillaries of the dermal papillae.

To leather derivatives human include: sweat, sebaceous, mammary glands, hair and nails. The mammary gland is functionally closely related to childbirth and is usually considered together with the genitals.

1) Sweat glands- simple tubular glands, lie in the reticular layer of the dermis at the border with the hypodermis and have the shape of glomeruli. Their excretory ducts pass through all layers of the skin and open on the surface with openings - sweat pores. Sweat glands in the skin are distributed unevenly. There are many of them in the armpits, groin areas, in the skin of the palms and soles. During the day, at an ambient temperature of 18-20°C, an average of 500 ml of sweat is released. Sweat consists of water (98%) and dense residue (2%), which contains organic and
inorganic substances.

2) Sebaceous glands- simple alveolar glands with branched terminal sections. They are located shallowly, at the border of the papilla- of the dermis and reticular layers. Their ducts usually open into the hair follicle, and where there is no hair, directly onto the surface of the skin. There are no sebaceous glands on the soles and palms. Per day greasy

The glands secrete about 20 g of sebum. Sebum contains fatty acids, cholesterol, glycerol, etc. It serves as a lubricant for the los, epidermis, protects the skin from water, microorganisms, softens and gives it elasticity.

3) Hair are derivatives of the epidermis and are present on almost the entire surface

skin. There are 3 types of hair: long (head hair, beards, mustaches, armpits, pubis), bristly (hair of the eyebrows, eyelashes, nostrils, external auditory canal) and vellus hair, covering the remaining areas of the skin (torso, limbs). Human hair is made They perform mainly a sensitive function and play a limited protective and insulating role. Hair has a shaft protruding above the surface of the skin and a root. The root ends in an extension - the hair follicle, which is the sprouting part of the hair. The hair root is located in the dermis in a connective tissue sac - the hair follicle. The sebaceous gland opens into the hair bursa and a muscle is woven into it - the hair lifter. When the muscle contracts, the hair straightens, the sebaceous gland is compressed and releases its secretion (sebum).

The lifespan of a hair is from 3-4 months (in the armpits, on the eyebrows, eyelashes) to 4-10 years (on the head). The usual hair growth per day is up to 0.5 mm. Not normal large number hair (about 50-100 per day) falls out constantly and unnoticeably. The amount of hair varies widely among different people. On average, per 1 cm 2 on the crown there are - There are up to 170-200 hairs, on the entire head - from 80 to 140 thousand, on the rest of the body - about 20 thousand hairs. Hair color depends on the presence of various pigments in it. When air bubbles appear in the hair and the pigment disappears, the hair turns grey.

4) Nails They are dense, horny, slightly curved plates located at the ends of the fingers on the back side. Nails Protect very sensitive fingertips and help grip small objects. The nail is divided into a root located in the nail fissure, a body and a free edge protruding beyond the nail bed. The skin folds that limit the nail from its root and sides are called the nail folds.

Nail growth occurs due to the growth layer of the nail bed. In this place, epithelial cells multiply and become keratinized. Growth rate nail is on average 0.1 mm per day. Complete regeneration of the nail takes about 170 days. The growth of nails on the toes is much slower than on the fingers.

The skin contains a large number of receptors, perceiving various irritations. It is like a powerful living a perceiving screen facing the outside world. Skin receptors have different shape and structure and are located in the skin at different depths. So, for example, pain receptors(there are from 2 to 4 million of them on the entire surface of the skin) are represented by free nerve endings located in the deep layers of the epidermis and in the papillary layer of the dermis. Temperature receptors: thermal - A. Ruffini's corpuscles (about 30,000 of them) and cold - V. Krause's flasks (about 250,000 of them) lie in the deep layers of the dermis and in the subcutaneous layer. Tactile receptors - receptors of touch and touch (there are about 5 million of them on the entire skin) include the tactile corpuscles of G. Meissner, located in the papillae of the skin.

Homework:

R.P. Samusev, Yu.M. Selin Human Anatomy, M. “Medicine” 1995. pp. 449-465.

I.V. Gaivorovsky, G.I. Nichiporuk, A. I. Gaivorovsky Human Anatomy and Physiology, M. Publishing center "Academy" 2011 pp.448-466.

V.Ya. Lipchenko, R.P. Samusev Atlas on human anatomy, M. "Alliance-V" 1998, pp. 306-318.

S.A. Georgieva Physiology, M., “Medicine”. 1982, pp. 433-451.

Developed by: Oksana Anatolyevna Medvedeva, Uryupinsk branch of the Volgograd Medical College

Analyzer is a term introduced by I.P. Pavlov to designate a functional unit responsible for receiving and analyzing sensory information of any one modality.

Collection of neurons different levels hierarchies involved in the perception of irritations, the conduction of excitation and the analysis of irritation.

The analyzer, together with a set of specialized structures (sensory organs) that facilitate the perception of information from the environment, is called the sensory system.

For example, the auditory system is a collection of very complex interacting structures, including the outer, middle, inner ear and a collection of neurons called the analyzer.

The concepts “analyzer” and “sensory system” are often used interchangeably.

Analyzers, like sensory systems, are classified according to the quality (modality) of the sensations in the formation of which they participate. These are visual, auditory, vestibular, gustatory, olfactory, skin, vestibular, motor analyzers, internal organ analyzers, somatosensory analyzers.

The analyzer has three sections:

1. A perceptive organ or receptor designed to convert the energy of stimulation into the process of nervous excitation;

2. A conductor consisting of afferent nerves and pathways through which impulses are transmitted to the overlying parts of the central nervous system;

3. The central section, consisting of relay subcortical nuclei and projection sections 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

Analyzers are special structures of the body that serve to input external information into the brain for its subsequent processing.

Minor terms

· receptors;

Structural diagram of terms

During work, the human body adapts to environmental changes thanks to the regulatory function of the central nervous system (CNS). Man is connected with the environment through analyzers, which consist of receptors, nerve pathways and the brain end in the cerebral cortex. The brain end consists of a nucleus and elements scattered throughout the cerebral cortex that provide nerve connections between individual analyzers. For example, when a person eats, he feels the taste, smell of food and feels its temperature.

The main characteristic of analyzers is sensitivity.

The lower absolute threshold of sensitivity is the minimum value of the stimulus to which the analyzer begins to respond.

In humans, receptors are tuned to the following stimuli:

· electromagnetic oscillations of the light range - photoreceptors in the retina of the eye;

· mechanical vibrations of air - phonoreceptors of the ear;

· changes in hydrostatic and osmotic blood pressure - baro- and osmoreceptors;

· change in body position relative to the gravity vector - receptors of the vestibular apparatus.

In addition, there are chemoreceptors (react to the effects of chemicals), thermoreceptors (perceive temperature changes both inside the body and in the environment), tactile receptors and pain receptors.

In response to changes in environmental conditions, so that external stimuli do not cause damage and death of the body, compensatory reactions are formed in it, which can be: behavioral (changing the place of stay, withdrawing the hand from hot or cold) or internal (changing the thermoregulation mechanism in response to change in microclimate parameters).

A person has a number of important specialized peripheral formations - sensory organs that provide perception of influences on the body. external stimuli. These include the organs of vision, hearing, smell, taste, and touch.

The concepts of “sense organs” and “receptor” should not be confused. For example, the eye is the organ of vision, and the retina is a photoreceptor, one of the components of the organ of vision. The sense organs themselves 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.

Visual analyzer includes the eye, optic nerve, visual center in the occipital part of the cerebral cortex. The eye is sensitive to the visible range of the electromagnetic wave spectrum from 0.38 to 0.77 microns. Within these limits, different wavelengths produce different sensations (colors) when applied to the retina:

0.38 - 0.455 microns - purple color;

0.455 - 0.47 microns - blue;

0.47 - 0.5 microns - blue color;

0.5 - 0.55 microns - green;

0.55 - 0.59 microns - yellow;

0.59 - 0.61 microns - orange;

0.61 - 0.77 microns - red color.

Adaptation of the eye to distinguish a given object under given conditions is carried out through three processes without the participation of human will.

Accommodation- changing the curvature of the lens so that the image of the object is in the plane of the retina (focusing).

Convergence- rotation of the visual axes of both eyes so that they intersect at the object of difference.

Adaptation- adaptation of the eye to a given level of brightness. During the adaptation period, the eye works with reduced performance, so it is necessary to avoid frequent and deep re-adaptation.

Hearing- the body’s ability to receive and distinguish sound vibrations with an auditory analyzer in the range from 16 to 20,000 Hz.

Smell- ability to perceive odors. Receptors are located in the mucous membrane of the upper and middle nasal passages.

Humans have varying degrees of sense of smell for different odorous substances. Pleasant odors improve a person’s well-being, while unpleasant odors have a depressing effect, cause negative reactions including nausea, vomiting, fainting (hydrogen sulfide, gasoline), can change skin temperature, cause aversion to food, lead to depression and irritability.

Taste- a sensation that occurs when certain chemicals, soluble in water, are exposed to taste buds located on different parts of the tongue.

Taste comes from four simple taste sensations: sour, salty, sweet and bitter. All other variations of taste are combinations of basic sensations. Different parts of the tongue have different sensitivity to taste substances: the tip of the tongue is sensitive to sweet, the edges of the tongue to sour, the tip and edge of the tongue to salty, the root of the tongue to bitter. The mechanism of perception of taste is associated with chemical reactions. It is assumed that each receptor contains highly sensitive protein substances that disintegrate when exposed to certain flavoring substances.

Touch- a complex sensation that occurs when skin receptors, external parts of the mucous membranes and the muscular-articular apparatus are irritated.

The skin analyzer perceives external mechanical, temperature, chemical and other skin irritants.

One of the main functions of the skin is protective. Sprains, bruises, and pressure are neutralized by the elastic fat layer and elasticity of the skin. The stratum corneum protects the deep layers of the skin from drying out and is very resistant to various chemicals. The pigment melanin protects the skin from exposure to ultraviolet rays. An intact layer of skin is impervious to infections, and sebum and sweat create a fatal acidic environment for microbes.

An important protective function of the skin is participation in thermoregulation, because 80% of all heat transfer from the body occurs through the skin. At high ambient temperatures, skin vessels expand and heat transfer by convection increases. At low temperatures, blood vessels narrow, the skin turns pale, and heat transfer decreases. Heat is also lost through the skin through sweating.

The secretory function is carried out through the sebaceous and sweat glands. Iodine, bromine, and toxic substances are released with sebum and sweat.

The metabolic function of the skin is participation in the regulation of general metabolism in the body (water, mineral).

The receptor function of the skin is perception from the outside and transmission of signals to the central nervous system.

Types of skin sensitivity: tactile, pain, temperature.

With the help of analyzers, a person receives information about the outside world, which determines the functioning of the functional systems of the body and human behavior.

The maximum speeds for transmitting information received by a person using various senses are given in table. 1.6.1

Table 1. Characteristics of sense organs

Perceived signal	Signal content	Maximum information transfer rate Bit\s
Visual	Line length. Color. Brightness	3,25; 3,1; 3,3
Auditory	Volume. Pitch	2,3; 2,5
Flavoring	Salinity	1,3
Olfactory	Intensity	1,53
Tactile (tactile)	Intensity. Duration. Location on the body	2,0; 2,3; 2,8

Analyzer– a combination of three parts of the nervous system: peripheral, conductive and central.

Peripheral section of the analyzer represented by receptors that perceive external and internal stimuli.

All receptors are divided into two groups: distant and contact. Distant receptors are capable of perceiving irritations, the source of which is located at a considerable distance from the body (visual, auditory, olfactory receptors). Contact receptors are excited by direct contact with a source of irritation. These include tactile, temperature, and taste buds.

Receptors transform the energy of stimulation into the energy of a nerve impulse. The cause of excitation in the receptor is the depolarization of its surface membrane as a result of exposure to a stimulus. This depolarization is called the receptor, or regenerative, potential.

Adaptation- adaptation to the strength of the stimulus. There is a decrease in the sensitivity of receptors to a constant stimulus. Proprioceptors are not capable of adaptation.

Conductor section of the analyzer represented by nerve pathways that conduct nerve impulses to the central part of the analyzer.

Central, or cerebral, section of the analyzer- certain areas of the cerebral cortex. In the cells of the cerebral cortex, nerve impulses are the basis for the occurrence of sensation. On the basis of sensations, more complex mental acts arise - perception, representation and abstract thinking.

Pavlov I.P. The brain end of the analyzer consists of two parts: the nucleus and peripheral scattered nerve elements located over the entire surface of the cerebral cortex.

The central part of the analyzer (nucleus) consists of functionally highly differentiated neurons that carry out higher analysis and synthesis of information coming to them. The scattered elements of the brain end of the analyzer are represented by less differentiated neurons capable of performing simple functions.

All analyzers are divided into external and internal. TO external analyzers include visual, auditory, gustatory, olfactory and skin . TO internal analyzers - motor, vestibular and internal organs analyzer (interoreceptive analyzer).

EXTERNAL ANALYZERS.

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. Optical system 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 – refraction of light in the optical media of the eye.

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

Field of view- corner space, visible 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. Mechanism color perception According to the generally accepted, but now outdated, three-component theory, 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. When the three primary colors are mixed in a certain way, the sensation of white appears. 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 a congenital color abnormality, a decrease in sensitivity to blue color is more often observed, and with an acquired color abnormality, a decrease in sensitivity to green is more often observed. Dalton 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. Peripheral department 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 through conductor path(auditory nerve) go to the temporal region of the cerebral cortex - the brain section of the analyzer. IN brain section The analyzer converts nerve impulses 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 hammer - is woven with its handle into the tympanic membrane, the other side of the hammer 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 vestibular apparatus , which is involved in regulating body position 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.

Meaning taste analyzer consists of testing food in direct contact with the mucous membrane of the oral cavity.

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 the back wall of the pharynx, soft palate, tonsils, and 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.

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

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. Wiring department 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. Brain section of the analyzer- 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, V maintaining balance, and also relates to the regulation of muscle tone.

Peripheral department 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. conductive path- vestibular nerve. Brain department 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 channels internal ear. The semicircular canals are narrow passages correct forms that are located in three mutually perpendicular planes. Upper, or front, channel lies in the frontal, posterior - V sagittal, and external - in the horizontal plane. One the end of each the canal is flask-shaped and is called the 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.

Peripheral department The motor analyzer is represented by proprioceptors located in muscles, tendons, ligaments and periarticular bursae. Wiring department consists of corresponding sensory nerves and pathways of the spinal cord and brain. Brain department 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).

Peripheral department formed by a variety of interoreceptors diffusely located in the internal organs. They are called visceroreceptors.

Conductive department includes several nerves of different functional significance that innervate the internal organs, vagus, celiac and splanchnic. Brain department 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- 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 irritations are perceived nociceptors located throughout the body, with the exception of the brain. Term nociception means the process of perception of damage.

When, upon irritation of cutaneous nociceptors, deep tissue nociceptors or internal organs of the body, the resulting impulses, following the classical anatomical pathways, reach higher departments nervous system and are reflected by consciousness, formed feeling of pain. The complex of the nociceptive system is equally balanced in the body by the complex antinociceptive system, providing control over the activity of 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 brain stem, nuclei 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 development mechanisms analgesia The greatest importance is attached to the serotonergic, noradrenergic, GABAergic and opioidergic systems of the brain. The main one is 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 a sprained ligament 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.