Which analyzers are external. Receptors share a number of common properties

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

Set of neurons different levels hierarchies involved in the perception of stimuli, the conduction of excitation, and in the analysis of stimulus.

The analyzer, together with the collection specialized structures(sense organs) that contribute to the perception of environmental information is called a 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.

Often the terms "analyzer" and "sensor system" are used as synonyms.

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

The term analyzer is used mainly in the countries of the former USSR.

The analyzer is divided into three sections :

1. Perceiving organ or receptor designed to convert the energy of irritation into the process of nervous excitation;

2. 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), along which the regulation of the activity of the lower levels of the analyzer from its higher, especially cortical, departments is carried out.

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

Minor terms

· receptors;

Block diagram of terms

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

The main characteristics of the analyzers - sensitivity .

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

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

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 of position of a body concerning a vector of gravitation - receptors of a vestibular device.

In addition, there are chemoreceptors (responding to exposure to chemical substances), 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 (change of location, withdrawal of the hand from hot or cold) or internal (change in the mechanism of thermoregulation in response to change in microclimate parameters).

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

Do not confuse the concepts of "sense organs" and "receptor". For example, the eye is the organ of vision, and the retina is the photoreceptor, one of the components of the organ of vision. The sense organs alone cannot provide sensation. For the occurrence of a subjective sensation, it is necessary that the excitation that has arisen 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 spectrum electromagnetic waves from 0.38 to 0.77 µm. Within these limits, different wavelength ranges cause different sensations (colors) when exposed to the retina:

0.38 - 0.455 µm - purple;

0.455 - 0.47 microns - blue;

0.47 - 0.5 microns - blue;

0.5 - 0.55 microns - green;

0.55 - 0.59 µm - yellow;

0.59 - 0.61 microns - orange;

0.61 - 0.77 microns - red.

The adaptation of the eye to the distinction of a given object under given conditions is carried out by three processes without the participation of the 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 axes of vision 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 period of adaptation, the eye works with reduced efficiency, so it is necessary to avoid frequent and deep re-adaptation.

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

The perceptive part of the auditory analyzer is the ear, which is divided into three sections: outer, middle and inner. Sound waves, penetrating into the external auditory meatus, vibrate the tympanic membrane and through the chain of auditory ossicles are transmitted to the cavity of the cochlea of the inner ear. Vibrations of the fluid in the canal cause the fibers of the main membrane to resonate with the sounds entering the ear. Vibrations of the cochlear fibers set in motion the cells of the organ of Corti located in them, a nerve impulse arises, which is transmitted to the corresponding sections of the cerebral cortex. Pain threshold 130 - 140 dB.

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

A person has a different degree of smell for various odorous substances. Pleasant odors improve a person’s well-being, while unpleasant odors act depressingly, cause negative reactions up to nausea, vomiting, fainting (hydrogen sulfide, gasoline), can change skin temperature, cause disgust for food, lead to depression and irritability.

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

Taste is made up of four simple taste sensations: sour, salty, sweet, and bitter. All other flavor variations are combinations of basic sensations. Various plots tongues 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 sensations is associated with chemical reactions. It is assumed that each receptor contains highly sensitive protein substances that decompose when exposed to certain flavoring substances.

Touch- a complex sensation that occurs when the receptors of the skin, the outer 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, pressures are neutralized by an elastic fatty lining and elasticity of the skin. The stratum corneum protects the deep layers of the skin from drying out and is highly resistant to various chemicals. The melanin pigment protects the skin from UV rays. The intact layer of skin is impervious to infections, while sebum and sweat create a deadly acidic environment for germs.

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

Secretory function is carried out through the sebaceous and sweat glands. With sebum and sweat, iodine, bromine, and toxic substances are released.

The metabolic function of the skin is participation in the regulation of the 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 work of the functional systems of the body and human behavior.

Maximum speeds transmission of information received by a person with the help of various sense organs are given in Table. 1.6.1

Table 1. Characteristics of the sense organs

The reaction of the human body to the influence of the external environment depends on the level of the acting stimulus. If this level is low, then the person simply perceives information from the outside. At high levels, undesirable biological effects appear. Therefore, normalized safe values of factors are established in production in the form of maximum permissible concentrations (MPC) or maximum permissible levels of energy exposure (MPL).

remote control- this is the maximum level of a factor that, acting on a person (in isolation or in combination with other factors) during a work shift, daily, throughout the entire length of service, will not cause biological changes in him and his offspring, even hidden and temporarily compensated, as well as psychological disorders (decrease in intellectual and emotional abilities, mental performance, reliability).

Conclusions on the topic

Normalized safe values of factors in the form of MPC and MPC are necessary to exclude irreversible biological effects in the human body.

The anterior part of the membranous labyrinth is the cochlear duct, ductus cochlearis, enclosed in the bony cochlea, is the most essential part of the organ of hearing. Ductus cochlearis begins with a blind end in the vestibule recessus cochlearis somewhat posterior to the ductus reuniens, which connects the cochlear duct with the sacculus. Then the ductus cochlearis passes through the entire spiral canal of the bony cochlea and ends blindly at its apex. On the cross section the cochlear duct has a triangular shape. One of its three walls grows together with the outer wall of the bony canal of the cochlea, the other, membrana spiralis, is a continuation of the bone spiral plate, stretching between the free edge of the latter and the outer wall. The third, very thin wall of the cochlear passage, paries vestibularis ductus cochlearis, stretches obliquely from the spiral plate to the outer wall.

Membrana spiralis on the basilar plate embedded in it, lamina basilaris, carries an apparatus that perceives sounds - a spiral organ. By means of the ductus cochlearis, the scala vestibuli and the scala tympani are separated from each other, with the exception of a place in the dome of the cochlea, where there is a communication between them, called the opening of the cochlea, helicotrema. Scala vestibuli communicates with the perilymphatic space of the vestibule, and scala tympani ends blindly at the window of the cochlea.

The spiral organ, organon spirale, is located along the entire cochlear duct on the basilar plate, occupying the part of it closest to the lamina spiralis ossea. The basilar plate, lamina basilaris, consists of a large number (24,000) of fibrous fibers of various lengths, stretched like strings (auditory strings). According to the well-known theory of Helmholtz (1875), they are resonators, which determine the perception of tones of different heights by their vibrations, but, according to electron microscopy, these fibers form an elastic network, which generally resonates with strictly graduated vibrations. The spiral organ itself is composed of several rows of epithelial cells, among which sensitive auditory cells with hairs can be distinguished. It acts as a "reverse" microphone, transforming mechanical vibrations into electrical ones.

The arteries of the inner ear come from a. labyrinthi, branches of a. basilaris. Walking with n. vestibulocochlearis in the internal auditory canal, a. labyrinthi branches in the ear labyrinth. Veins carry blood out of the labyrinth mainly in two ways: v. aqueductus vestibuli, which lies in the canal of the same name along with the ductus endolymphaticus, collects blood from the utriculus and semicircular canals and flows into the sinus petrosus superior, v. canaliculi cochleae, which passes along with the ductus perilymphaticus in the canal of the cochlear aqueduct, carries blood mainly from the cochlea, as well as from the vestibule from the sacculus and utriculus, and flows into v. jugularis interna.

Ways of conducting sound.

From a functional point of view, the organ of hearing (the peripheral part of the auditory analyzer) is divided into two parts:

1) the sound-conducting apparatus - the outer and middle ear, as well as some elements (perilymph and endolymph) of the inner ear; 2) the sound-receiving apparatus - the inner ear.

Air waves collected by the auricle are sent to the external auditory canal, hit the eardrum and cause it to vibrate. Vibration of the tympanic membrane, the degree of tension of which is regulated by the contraction m. tensor tympani (innervation from n. trigeminus), sets in motion the handle of the malleus fused with it. The hammer respectively moves the anvil, and the anvil moves the stirrup, which is inserted into the fenestra vestibuli leading to the inner ear. The amount of the stirrup displacement in the vestibule window is regulated by the contraction m. stapedius (innervation from n. stapedius from n. facialis). Thus, the ossicular chain, which is movably connected, transmits the oscillatory movements of the tympanic membrane towards the window of the vestibule.

The movement of the stirrup in the window of the vestibule inward causes the movement of the labyrinth fluid, which protrudes the membrane of the window of the cochlea outwards. These movements are necessary for the functioning of the highly sensitive elements of the spiral organ. The perilymph of the vestibule moves first; its vibrations along the scala vestibuli ascend to the top of the cochlea, through the helicotrema are transmitted to the perilymph in the scala tympani, descend along it to the membrana tympani secundaria, which closes the window of the cochlea, which is a weak point in the bone wall of the inner ear, and, as it were, returns to the tympanic cavity. From the perilymph, sound vibration is transmitted to the endolymph, and through it to the spiral organ. Thus, air vibrations in the outer and middle ear, thanks to the system of auditory ossicles of the tympanic cavity, turn into fluctuations in the fluid of the membranous labyrinth, causing irritation of special auditory hair cells of the spiral organ that make up the auditory analyzer receptor.

In the receptor, which is, as it were, a "reverse" microphone, the mechanical vibrations of the fluid (endolymph) turn into electrical vibrations that characterize the nervous process that propagates along the conductor to the cerebral cortex. The conductor of the auditory analyzer is made up of auditory pathways, consisting of a number of links.

The cell body of the first neuron lies in the ganglion spirale. The peripheral process of its bipolar cells in the spiral organ begins with receptors, and the central one goes as part of the pars cochlearis n. vestibulocochlearis to its nuclei, nucleus cochlearis dorsalis et ventralis, laid in the region of the rhomboid fossa. Different parts of the auditory nerve conduct sounds of different frequencies.

The bodies of the second neurons are placed in these nuclei, the axons of which form the central auditory pathway; the latter in the region of the posterior nucleus of the trapezoid body intersects with the homonymous path of the opposite side, forming a lateral loop, lemniscus lateralis. The fibers of the central auditory pathway, coming from the ventral nucleus, form the trapezoid body and, having passed the bridge, are part of the lemniscus lateralis of the opposite side. The fibers of the central pathway, originating from the dorsal nucleus, go along the bottom of the IV ventricle in the form of striae medullares ventriculi quarti, penetrate the formatio reticularis of the bridge, and, together with the fibers of the trapezoid body, enter into the lateral loop of the opposite side. Lemniscus lateralis ends partly in the lower colliculus of the roof of the midbrain, partly in the corpus geniculatum mediale, where the third neurons are placed.

The lower colliculus of the roof of the midbrain serves as a reflex center for auditory impulses. From them goes to the spinal cord tractus tectospinalis, through which motor reactions are performed to auditory stimuli entering the midbrain. Reflex responses to auditory impulses can also be obtained from other intermediate auditory nuclei - the nuclei of the trapezoid body and the lateral loop, connected by short paths with the motor nuclei of the midbrain, bridge and medulla oblongata.

Terminating in formations related to hearing (inferior colliculi and corpus geniculatum mediale), the auditory fibers and their collaterals join, in addition, to the medial longitudinal bundle, through which they come in contact with the nuclei of the oculomotor muscles and with the motor nuclei of other cranial nerves and spinal cord. These connections explain the reflex responses to auditory stimuli.

The lower colliculi of the roof of the midbrain do not have centripetal connections with the cortex. In the corpus geniculatum mediale lie the cell bodies of the last neurons, the axons of which, as part of the internal capsule, reach the cortex of the temporal lobe of the brain. The cortical end of the auditory analyzer is located in the gyrus temporalis superior (field 41). Here, the air waves of the outer ear, which cause the movement of the auditory ossicles in the middle ear and fluctuations in the fluid in the inner ear and are further converted in the receptor into nerve impulses transmitted through the conductor to the cerebral cortex, are perceived as sound sensations. Consequently, thanks to the auditory analyzer, air vibrations, i.e., an objective phenomenon of the real world that exists independently of our consciousness, is reflected in our consciousness in the form of subjectively perceived images, i.e., sound sensations.

This is a vivid example of the validity of Lenin's theory of reflection, according to which the objectively real world is reflected in our minds in the form of subjective images. This materialistic theory exposes subjective idealism, which, on the contrary, puts our sensations in the first place.

Thanks to the auditory analyzer, various sound stimuli, perceived in our brain in the form of sound sensations and complexes of sensations - perceptions, become signals (the first signals) of vital environmental phenomena. This constitutes the first signal system of reality (IP Pavlov), i.e., concrete-visual thinking, which is also characteristic of animals. A person has the ability to abstract, abstract thinking with the help of a word that signals sound sensations, which are the first signals, and therefore is a signal of signals (second signal). Hence, oral speech constitutes the second signal system of reality, peculiar only to man.

Human analyzers - types, characteristics, functions

Human analyzers help in obtaining and processing information that the sense organs receive from the environment or internal environment.

How does a person perceive the world around him - incoming information, smells, colors, tastes? All this is provided by human analyzers, which are located throughout the body. They are different types and have different characteristics. Despite the differences in structure, they perform one general function- to perceive and process information, which is then transmitted to a person in a form that is understandable to him.

Analyzers are just devices through which a person perceives the world around him. They work without the conscious participation of a person, sometimes they are amenable to his control. Depending on the information received, a person understands what he sees, eats, smells, what environment he is in, etc.

Human analyzers

Human analyzers are called nervous formations that provide reception and processing of information received from the internal environment or the external world. Together with, which perform specific functions, they form a sensory system. Information is perceived by the nerve endings that are located in the sensory organs, then passes through the nervous system directly to the brain, where it is processed.

Human analyzers are divided into:

External - visual, tactile, olfactory, sound, taste.
Internal - perceive information about the state of internal organs.

The analyzer is divided into three sections:

Perceiving - a sense organ, a receptor that perceives information.
Intermediate - conducting information further along the nerves to the brain.
Central - nerve cells in the cerebral cortex, where the received information is processed.

The peripheral (perceiving) department is represented by sensory organs, free nerve endings, receptors that perceive a certain type of energy. They translate irritation into a nerve impulse. In the cortical (central) zone, the impulse is processed into a sensation that is understandable to a person. This allows him to quickly and adequately respond to changes that occur in the environment.

If all analyzers of a person work at 100%, then he adequately and timely perceives all incoming information. However, problems arise when the susceptibility of the analyzers deteriorates, and the conduction of impulses along the nerve fibers is also lost. The website of the psychological help site indicates the importance of monitoring your senses and their condition, since this affects a person's susceptibility and his full understanding of what is happening in the world around him and inside his body.

If the analyzers are damaged or do not function, then the person has problems. For example, an individual who does not feel pain may not notice that he was seriously injured, he was bitten poisonous insect etc. The lack of an immediate reaction can lead to death.

Types of human analyzers

The human body is full of analyzers that are responsible for receiving this or that information. That is why human sensory analyzers are divided into types. It depends on the nature of the sensations, the sensitivity of the receptors, the destination, the speed, the nature of the stimulus, etc.

External analyzers are aimed at perceiving everything that happens in the external world (outside the body). Each person subjectively perceives what is in the outside world. Thus, color-blind people cannot know that they cannot distinguish certain colors until other people tell them that the color of a particular object is different.

External analyzers are divided into the following types:

Visual.
Taste.
Auditory.
Olfactory.
Tactile.
Temperature.

Internal analyzers are engaged in maintaining a healthy state of the body inside. When the state of a particular organ changes, a person understands this through the corresponding unpleasant sensations. Every day a person experiences sensations that are consistent with the natural needs of the body: hunger, thirst, fatigue, etc. This prompts a person to perform a certain action, which allows the body to be balanced. In a healthy state, a person usually does not feel anything.

Separately, kinesthetic (motor) analyzers and the vestibular apparatus are distinguished, which are responsible for the position of the body in space and its movement.

Pain receptors are engaged in notifying a person that specific changes have occurred inside the body or on the body. So, a person feels that he has been hurt or hit.

Violation of the analyzer's work leads to a decrease in the susceptibility of the surrounding world or internal state. Usually problems arise with external analyzers. However, a violation of the vestibular apparatus or damage to pain receptors also causes certain difficulties in perception.

Characteristics of human analyzers

The primary characteristic of human analyzers is their sensitivity. There are high and low sensitivity thresholds. Each person has his own. Ordinary pressure on the hand can cause pain in one person and a slight tingling in another, depending entirely on the sensitive threshold.

Sensitivity is absolute and differentiated. The absolute threshold indicates the minimum strength of irritation that is perceived by the body. A differentiated threshold helps in recognizing minimal differences between stimuli.

The latent period is the period of time from the onset of exposure to the stimulus to the appearance of the first sensations.

The visual analyzer is involved in the perception of the surrounding world in a figurative form. These analyzers are the eyes, where the size of the pupil, the lens changes, which allows you to see objects in any light and distance. Important features of this analyzer are:

Changing the lens, which allows you to see objects both near and far.
Light adaptation - getting used to the eye lighting (takes 2-10 seconds).
Sharpness is the separation of objects in space.
Inertia is a stroboscopic effect that creates the illusion of continuous movement.

Disorder of the visual analyzer leads to various diseases:

Color blindness is the inability to perceive red and green colors, sometimes yellow and purple.
Color blindness is the perception of the world in gray.
Hemeralopia is the inability to see at dusk.

The tactile analyzer is characterized by points that perceive various effects of the surrounding world: pain, heat, cold, shocks, etc. The main feature is skin to the external environment. If the irritant constantly affects the skin, then the analyzer reduces its own sensitivity to it, that is, it gets used to it.

The olfactory analyzer is the nose, which is covered with hairs that perform a protective function. In respiratory diseases, immunity to odors that enter the nose can be traced.

The taste analyzer is represented by nerve cells located on the tongue that perceive tastes: salty, sweet, bitter and sour. Their combination is also noted. Each person has their own susceptibility to certain tastes. That is why all people have different tastes, which can differ by up to 20%.

Functions of human analyzers

The main function of human analyzers is the perception of stimuli and information, transmission to the brain so that specific sensations arise that prompt appropriate actions. The function is to communicate so that the person automatically or consciously decides what to do next or how to fix the problem that has arisen.

Each analyzer has its own function. Together, all analyzers create a general idea of what is happening in the outside world or inside the body.

The visual analyzer helps to perceive up to 90% of all information of the surrounding world. It is transmitted by pictures that help to quickly orientate in all sounds, smells and other irritants.

Tactile analyzers perform a defensive and protective function. Various foreign bodies get on the skin. Their different effects on the skin make a person quickly get rid of what can harm the integrity. The skin also regulates body temperature by alerting the environment in which a person finds himself.

The organs of smell perceive odors, and the hairs perform a protective function to rid the air of foreign bodies in the air. Also, a person perceives the environment by smell through the nose, controlling where to go.

Taste analyzers help in recognizing the tastes of various objects that enter the mouth. If something tastes edible, the person eats. If something doesn't match the taste buds, the person spits it out.

The appropriate body position is determined by the muscles that send signals and tighten when moving.

The function of the pain analyzer is to protect the body from pain-causing stimuli. Here a person either reflexively or consciously begins to defend himself. For example, pulling your hand away from a hot kettle is a reflex reaction.

Auditory analyzers perform two functions: the perception of sounds that can notify of danger, and the regulation of the balance of the body in space. Diseases of the hearing organs can lead to a violation of the vestibular apparatus or distortion of sounds.

Each organ is directed to the perception of a certain energy. If all receptors, organs and nerve endings are healthy, then a person perceives himself and the world around him in all its glory at the same time.

Forecast

If a person loses the functionality of his analyzers, then the prognosis of his life worsens to some extent. There is a need to restore their functionality or replace them in order to compensate for the deficiency. If a person loses his sight, then he has to perceive the world through other senses, and other people or a guide dog become “his eyes”.

Doctors note the need for hygiene and preventive treatment of all their senses. For example, you need to clean your ears, not eat what is not considered food, protect yourself from exposure to chemicals, etc. There are many irritants in the outside world that can harm the body. A person must learn to live in such a way as not to damage his sensory analyzers.

The result of loss of health when internal analyzers signal pain, which indicates a painful condition of a particular organ, death can become. Thus, the performance of all human analyzers helps in saving life. Damage to the senses or ignoring their signals can significantly affect life expectancy.

For example, damage to up to 30-50% of the skin can lead to the death of a person. Hearing damage will not lead to death, however, it will reduce the quality of life when a person cannot fully experience the whole world.

It is necessary to monitor some analyzers, periodically check their performance and carry out preventive maintenance. There are certain measures that help in maintaining vision, hearing, tactile sensitivity. Much also depends on the genes that are passed on to children from their parents. It is they who determine how sharp in sensitivity the analyzers will be, as well as their perception threshold.

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 are processed by the brain - the central part.

Departments

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

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

Rice. 1. Departments of analyzers.

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

Kinds

Receptors, and accordingly analyzers, can be two kinds:

external (exteroceptors) - are 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 of the internal environment.

Rice. 2. The location of the centers of perception in the brain.

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

*Analyzer*	*Receptors*	*Conducting paths*	*Central departments*
Visual	Retinal photoreceptors	optic nerve	Occipital lobe of the cerebral cortex
Auditory	Hair cells of the spiral (Corti) organ of the cochlea	Auditory nerve	Superior temporal lobe
Taste	Language receptors	Glossopharyngeal nerve	Anterior temporal lobe
Tactile	Receptor cells: - on bare skin - Meissner's bodies, which lie in the papillary layer of the skin; On the hair surface - hair follicle receptors; Vibrations - Pacinian bodies	Musculoskeletal nerves, back, medulla oblongata, diencephalon
Olfactory	Receptors in the nasal cavity	Olfactory nerve	Anterior temporal lobe
Temperature	Thermal (Ruffini bodies) and cold (Krause flasks) receptors	Myelinated (cold) and unmyelinated (heat) fibers	Posterior central gyrus of the parietal lobe

Rice. 3. Location of receptors in the skin.

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

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, which makes it possible to distinguish stimuli by intensity;
adaptation that 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 to perceive the completeness of the external world.

An example of a feature of the analyzer is the smell of paint. People with a low threshold for odors will smell more strongly and respond actively (lacrimation, nausea) than people with a high threshold. The analyzers will perceive a strong odor more intensely than other surrounding odors. Over time, the smell will not be felt sharply, because. adaptation will take place. If you constantly stay in a room with paint, then the sensitivity will become dull. However, after leaving the room for fresh air, for some time you will feel the smell of paint “imagining”.

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

The eye consists of an eyeball and an auxiliary apparatus. The wall of the eyeball is formed by three membranes: the cornea, sclera, or protein, and vascular. The inner (vascular) membrane 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, the lens and the vitreous body. For a clear vision of an object, it is necessary that the rays from all its points fall on the retina. The adaptation of the eye to a clear vision of 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 - the angular space visible to the eye with a fixed gaze and a motionless head.

On the retina are photoreceptors: rods (with the pigment rhodopsin) and cones (with the pigment iodopsin). Cones provide daytime vision and color perception, rods - twilight, 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 there are three sensors in the visual system that are sensitive to three primary colors: red, yellow and blue. Therefore, normal color perception is called trichromasia. With a certain mixture of the three primary colors, a sensation of white appears. If one or two primary color sensors fail, the correct mixing of colors is not observed and color perception disorders occur.

There are congenital and acquired forms of color anomalies. With congenital color anomaly, a decrease in sensitivity to blue color, and when acquired - to green. Color anomaly Dalton (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 essentially depends on the processing of the received signals by the brain.

auditory analyzer.

The value of the auditory analyzer lies in the perception and analysis of sound waves. The peripheral part 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-catching (outer ear) and sound-transmitting apparatus (middle ear). Nerve impulses generated in the receptors of the spiral organ go through the conduction path (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 organ of hearing includes the outer, middle and inner ear.

The structure of the outer ear. The outer ear consists of the auricle and the external auditory meatus.

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

The structure of the middle ear. The structure of the middle ear includes a system of auditory ossicles - hammer, anvil, stirrup, 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 anvil is connected to the stirrup, which is adjacent to the membrane of the window of the vestibule (foramen ovale) of the inner wall of the middle ear.

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

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

The structure of the inner ear. The composition of the inner ear (labyrinth) includes the vestibule, semicircular canals and the cochlea, in which special receptors are located 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 the regulation of body position in space and maintaining balance.

On the main membrane of the middle course of the cochlea there is a sound-perceiving apparatus - a spiral organ. It consists of receptor hair cells, the vibrations of which are converted into nerve impulses that propagate along the fibers of the auditory nerve and enter the temporal lobe of the cerebral cortex. The neurons of the temporal lobe of the cerebral cortex come into a state of excitation, and there is a sensation of sound. This is how air conduction of sound occurs.

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 is carried out through the bones of the skull. Sound vibrations are well conducted by the bones of the skull, are transmitted immediately to the perilymph of the upper and lower cochlea of the inner ear, and then to the endolymph of the middle course. There is an oscillation of the main membrane with hair cells, 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 than bone conduction.

Taste and olfactory analyzers.

The value of the taste analyzer lies in the approbation of food in direct contact with the oral mucosa.

Taste receptors (peripheral) are embedded in the epithelium of the oral mucosa. Nerve impulses along the conduction path, 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. Most taste buds are found at the tip, edges, and back of the tongue. Taste receptors are also located on the back of the pharynx, soft palate, tonsils, epiglottis.

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

The olfactory analyzer takes part in the determination of 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 through the conduction section - the olfactory nerve - enter the brain section of the analyzer - the region of the hook and hippocampus of the limbic system. In the cortical section of the analyzer, various olfactory sensations arise.

The olfactory receptors are concentrated in the region of the upper nasal passages. There are cilia on the surface of the olfactory cells. This increases the possibility of their contact with the molecules of odorous substances. The olfactory receptors are very sensitive. So, to obtain a sense of smell, it is enough that 40 receptor cells are excited, and only one molecule of an odorous substance should 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. In the future, the sense of smell weakens. The amount of mucus in the nasal cavity also affects the excitability of olfactory receptors. With increased secretion of mucus, for example during a runny nose, there is a decrease in the sensitivity of olfactory receptors to odorous substances.

Tactile and temperature analyzers.

The activity of the tactile analyzer is associated with the distinction between 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 are excited by touching or pressure on them. The conductor section of the tactile analyzer is represented by sensitive nerve fibers coming from receptors in the spinal cord (through the posterior roots and posterior columns), the medulla oblongata, the optic tubercles and neurons of the reticular formation. The brain section of the analyzer is the posterior central gyrus. It has tactile sensations.

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

Temperature analyzer. Its significance lies in determining the temperature of the external and internal environment of the body.

The peripheral section of this analyzer is formed by thermoreceptors. A change in the temperature of the internal environment of the body leads to the excitation of temperature receptors located in the hypothalamus. The conduction section of the analyzer is represented by the spinothalamic pathway, the fibers of which end in the nuclei of the visual tubercles 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 bodies, cold receptors are represented by Krause flasks.

Thermoreceptors in the skin are located at different depths: cold receptors are more superficial, thermal 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 part of the analyzer is represented by receptors located in the vestibular apparatus. They are excited by changing the speed of rotational movement, rectilinear acceleration, changing the direction of gravity, vibration. The conduction path is the vestibular nerve. The brain section of the analyzer is located in the anterior sections of the temporal lobe of the CG. As a result of excitation of the neurons of this section of the cortex, sensations arise that give ideas about the position of the body and its individual parts in space, contributing to maintaining balance and maintaining 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 the correct form, which are located in three mutually perpendicular planes. The upper, or anterior, channel lies in the frontal, the posterior - in the sagittal, and the external - in the horizontal plane. One end of each canal 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 a change in the speed of the body.

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

The peripheral part of the motor analyzer is represented by proprioceptors located in muscles, tendons, ligaments and periarticular bags. The conduction section consists of the corresponding sensory nerves and pathways of the spinal cord and brain. The brain department 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 found among muscle fibers, bulbous bodies (Golgi) located in tendons, lamellar bodies found in fascia covering muscles, tendons, ligaments and periosteum. A change in the activity of various proprioceptors occurs at the time of muscle contraction or relaxation. Muscle spindles are always in a state of some excitation. Therefore, nerve impulses constantly flow from muscle spindles to the central nervous system, to the spinal cord. This leads to the fact that the motor nerve cells - the 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 conductor section includes several nerves of different functional significance that innervate the internal organs, vagus, celiac and splanchnic pelvic. The medulla is located in the motor and premotor areas of the CG. 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 interoreceptors to the brain section of the analyzer are not converted into sensations, that is, they do not reach the threshold of our consciousness. However, when some visceroreceptors are excited, for example, the receptors of the bladder and rectum, if their walls are stretched, there are sensations of the urge to urinate and defecate.

Visceroreceptors are involved in the regulation of the work of internal organs, carry out reflex interactions between them.

Pain is a physiological phenomenon that informs us about harmful effects damaging or representing a potential hazard 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 perceiving damage.

When, upon stimulation of skin nociceptors, nociceptors of deep tissues or internal organs of the body, the resulting impulses, following the classical anatomical pathways, reach the higher parts of the nervous system and are displayed 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 provides a decrease in 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 (periaductal gray matter, raphe nuclei of the brainstem, nuclei of the reticular formation, nucleus of the thalamus, internal capsule, cerebellum, interneurons of the posterior horns of the spinal cord, etc. ) exerting a downward inhibitory effect on the transmission of nociceptive afferentation in the dorsal horns of the spinal cord.

In the mechanisms of the development of analgesia, the greatest importance is attached to the serotonergic, noradrenergic, GABAergic and opioidergic systems of the brain. The main of them, 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 just as important to normal functioning as the pain-signaling system. Thanks to her, minor injuries such as a finger bruise or sprain cause severe pain only on a short time- from a few minutes to several hours, without making us suffer for days and weeks, which would happen in conditions of persisting pain until complete healing.

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 collection of neurons involved in the perception of stimuli, the conduction of excitation, and in the analysis of stimulus.

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

Rice. Analyzers

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

Peripheral department: a receptor designed to convert the energy of irritation into a process of nervous excitation.
conductor department: a chain of centripetal (afferent) and intercalary neurons, along which impulses are transmitted from receptors to the overlying parts of the central nervous system.
Central department: a specific area of the cerebral cortex.

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

KBP*- the cerebral cortex.

sense organs

A person has a number of important specialized peripheral formations - sense organs that provide perception of external stimuli affecting the body.

The sense organ is made up of receptors and auxiliary device, which helps to capture, concentrate, focus, direct, etc. the signal.

The sense organs include the organs of sight, hearing, smell, taste, and touch. By themselves, they cannot provide sensation. For the occurrence of a subjective sensation, it is necessary that the excitation that has arisen 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, then 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, musculoskeletal 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 they mature earlier than others in ontogeny.

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

With the destruction of the primary fields, the so-called cortical blindness, cortical deafness, etc.

Secondary fields located next to the primary and connected through them with the senses.

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

When secondary fields are affected, 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 analyzer overlap zones, 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 terminate 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 physical activity.

These fields are present 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 unification of information from which occurs in tertiary fields.

With congenital underdevelopment of 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 association areas.

All sensory and motor areas occupy less than 20% of the cortical surface. The rest of the cortex makes up the association area.

Association zones

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

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

Rice. Furrows and lobes of the cerebral cortex

Rice. Association areas of the cerebral cortex:

1. Ass ocative engine zone(frontal lobe)

2. Primary motor zone

3. Primary somatosensory zone

4. Parietal lobe of the cerebral hemispheres

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

6.Associative visual area(occipital lobe)

7. Occipital lobe of the cerebral hemispheres

8. Primary visual area

9. Associative auditory zone(temporal lobes)

10. Primary auditory zone

11. Temporal lobe of the cerebral hemispheres

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

13. Taste bark

14. Prefrontal association area

15. Frontal lobe of the cerebral hemispheres.

Sensory signals in the association area are deciphered, interpreted and used to determine the most appropriate responses that are transmitted to the motor (motor) area associated with it.

Thus, associative zones are involved in the processes of memorization, learning and thinking, and the results of their activities are intelligence(the ability of the organism to use the acquired knowledge).

Separate large associative areas are located in the cortex next to the corresponding sensory areas. For example, the visual association area is located in the occipital area directly in front of the sensory visual area and performs complete processing of visual information.

Some associative zones perform only part of the information processing and are associated with other associative centers that perform further processing. For example, the audio association area analyzes sounds into categories and then relays signals to more specialized areas, such as the speech association area, where the meaning of the words heard is perceived.

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

In the cerebral cortex, areas with less defined functions are distinguished. So, a significant part of the frontal lobes, especially on the right side, can be removed without noticeable damage. However, if 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 carry taste buds on the lateral surface (Fig. 1, 2), which include 30 - 80 sensitive cells. Taste cells are dotted with microvilli at their ends. taste hairs. They reach the surface of the tongue through the taste pores. Taste cells are constantly dividing and constantly dying. Particularly fast is the replacement of cells located in the anterior part of the tongue, where they lie more superficially.

Rice. 2. Taste bulb: 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 - the tip of the tongue; bitter - the basis of the tongue; sour - lateral surface of the tongue; salty - the tip of the tongue.

Taste sensations are caused only by substances dissolved in water.

conductor 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;
approbation of food for edibility;
setting the digestive apparatus for food processing (according to the conditioned reflex mechanism);
defensive behavior (including the manifestation of aggression).

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

Conductor department: olfactory nerve.

Central department: the olfactory bulb (the forebrain structure 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 determined and an adequate reaction of the body to it is formed.

The perception of taste and smell complement each other, giving a holistic view of the type and quality of food. Both analyzers are connected with the center of salivation of the medulla oblongata and participate in the food reactions of the body.

The tactile and muscle analyzer are combined into somatosensory system- system of skin-muscular sensitivity.

The structure of the somatosensory analyzer

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

conductor 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 sensitive organ in the human body. Many receptors are concentrated on its surface (about 2 m2).

Most scientists tend to have four main types of skin sensitivity: tactile, heat, cold and pain.

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

SKIN MECHANORECEPTERS

thin nerve fiber endings, braiding blood vessels, hair bags, etc.
Merkel cells- nerve endings of the basal layer of the epidermis (many on the fingertips);
Meissner's tactile corpuscles- complex receptors of the papillary layer of the 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 the tendons, ligaments and mesentery;
bulbs (Krause flasks)- nerve receptorsconnective tissue layer of mucous membranes, under the epidermis and among the muscle fibers of the tongue.

MECHANISM OF OPERATION OF MECHANORECEPTERS

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

ADAPTATION OF SKIN MECHANORECEPTERS

fast adapting receptors: skin mechanoreceptors in hair follicles, lamellar bodies (we do not feel the pressure of clothes, contact lenses, etc.);
slowly adapting receptors:tactile bodies of Meissner.

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

The ability of a person to separately perceive touch to two adjacent points of the skin also differs greatly in different parts of it. 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 temperature of the human body fluctuates within relatively narrow limits; therefore, information about the ambient temperature, which is necessary for the activity of thermoregulation mechanisms, is of particular importance.

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

TYPES OF THERMORECEPTERS

cold thermoreceptors: numerous; lie close to the surface.
thermal thermoreceptors: they are much less; lie in the deeper layer of the 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 steadily lasts for the entire duration of the stimulus. A change in temperature by 0.2 °C causes long-term changes in their impulsation.

Under certain conditions, cold receptors can be excited by heat, and warm by cold. This explains the occurrence of an acute sensation of cold during rapid immersion in 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 the 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 organism, being a signal of danger under strong influences of various factors.

Pain receptor impulses often indicate pathological processes in the body.

On the this moment specific pain receptors have not been found.

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

Exist specific pain receptors - free nerve endings with a high reaction threshold;
Specific pain receptors does not exist; pain occurs with superstrong irritation of any receptors.

The mechanism of excitation of receptors during pain exposure has not yet been elucidated.

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

One of possible causes prolonged burning pain can 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, so the highest center of pain sensitivity is the thalamus, where 60% of neurons in the corresponding nuclei clearly respond to pain 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 very 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 irritations cause a number of reflex somatic and vegetative reactions. With moderate severity, these reactions have an adaptive value, but can lead to severe pathological effects, such as shock. Among these reactions, there is an increase in muscle tone, heart rate and respiration, an increase or decrease in pressure, constriction of the pupils, an increase in blood glucose and a number of other effects.

LOCALIZATION OF PAIN SENSITIVITY

With painful effects on the skin, a person localizes them quite accurately, but with diseases of the internal organs, referred pain. For example, with renal colic, patients complain of "incoming" sharp pains in the legs and rectum. There may be reverse effects as well.

proprioception

Types of proprioceptors:

neuromuscular spindles: provide information about the speed and strength of muscle stretching and contraction;
Golgi tendon receptors: provide information about the strength of muscle contraction.

Functions of proprioceptors:

perception of mechanical stimuli;
perception of the spatial arrangement of body parts.

NEURO-MUSCULAR SPINDLE

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

The neuromuscular spindle is located in the thickness of the muscle. Each spindle is covered with a capsule. Inside the capsule is a bundle of special muscle fibers. The spindles are located parallel to the fibers of skeletal muscles, therefore, 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 junction of muscle fibers with the tendon.

Tendon receptors respond poorly to muscle stretch, 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 are less studied than muscle. It is known that articular receptors respond to the position of the joint and to changes in the articular angle, thus participating in the feedback system from the motor apparatus and in its control.

The visual analyzer includes:

peripheral: retinal receptors;
conduction department: 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 is made up of eyeball and auxiliary apparatus.

Auxiliary apparatus of the eye

brows- sweat protection;
eyelashes- dust protection;
eyelids - mechanical protection and maintaining humidity;
lacrimal glands- located at the top of the outer edge of the orbit. It secretes tear fluid that moisturizes, flushes and disinfects the eye. Excess tear fluid is expelled into the nasal cavity through tear duct located in the inner corner of the eye socket .

EYEBALL

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

It is located on a fat padin the anterior part of the eye.

The eye has three shells:

white coat ( sclera) with transparent cornea- outer very dense fibrous membrane of the eye;
choroid with external iris and ciliary body- permeated with blood vessels (nutrition of the eye) and contains a pigment that prevents light from scattering through the sclera;
retina (retina) - the inner shell 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 that connects the eyeball with the skin.

Protein membrane (sclera)- outer tough shell of the eye; the inner part of the sclera is impervious to set rays. Function: eye protection from external influences and light isolation;

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

lens- a biconvex lens located behind the cornea. The function of the lens: focusing light rays. The lens has no blood vessels or nerves. It does not develop inflammatory processes. It contains a lot of proteins, which can sometimes lose their transparency, which leads to a disease called cataract.

choroid- the middle shell 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- a round hole in the iris. Function: regulation of the light flux entering the eye. Pupil diameter changes involuntarily using smooth muscles of the iriswhen the illumination changes.

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

Ciliary (ciliary) body- part of the middle (vascular) membrane of the eye; function: fixation of the lens, ensuring the process of accommodation (change in curvature) of the lens; production of aqueous humor of 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 branches of the endings of the optic nerve, which, approaching the eyeball, passes through the tunica albuginea, and the tunic of the nerve merges with the albuginea of the eye. Inside the eye, the nerve fibers are distributed in the form of a thin retina that lines the posterior 2/3 of the inner surface of the eyeball.

The retina is made up of supporting cells that form a mesh structure, hence its name. Light rays are perceived only by its rear part. The retina in its development and function is part of the nervous system. All other parts of the eyeball play an auxiliary role for the perception of visual stimuli by the retina.

Retina- this is the part of the brain that is pushed outward, closer to the surface of the body, and keeps in touch with it with the help of a pair of optic nerves.

Nerve cells form circuits 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 - multipolar neurons ( ganglion cells); axons depart from them, which stretch along the bottom of the eye and form the optic nerve.

Light-sensitive elements of the retina:

sticks- perceive brightness;
cones- perceive color.

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

The rods and cones in the retina of the eye are mixed with each other, but in some places they are very densely located, in others they are rare or absent altogether. Each nerve fiber has approximately 8 cones and approximately 130 rods.

In area yellow spot there are no rods on the retina - only cones, here the eye has the greatest visual acuity and the best perception of color. Therefore, the eyeball is in continuous motion, so that the considered part of the object falls on the yellow spot. As the distance from the macula increases, the density of the rods increases, but then decreases.

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

From rods and cones, nerve fibers depart, which, when combined, form the optic nerve. The exit point of the optic nerve from the retina is called optic disc. There are no photosensitive elements in the region of the optic nerve head. Therefore, this place does not give a visual sensation and is called blind spot.

MUSCLES OF THE EYE

oculomotor muscles- three pairs of striated skeletal muscles that attach to the conjunctiva; carry out the 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 flow of rays, and in weak light, it expands, making it possible for more rays to penetrate. The hormone adrenaline affects the diameter of the pupil. When a person is in an excited state (with 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 expand or contract in the same way. Even if only one eye is exposed to bright light, 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).

conductor department

The optic nerve is a conductor of 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 exits the orbit and, entering the cranial cavity, through the optic canal, together with the same nerve on the other side, forms a decussation ( chiasma) below the hypolamus. After decussation, the optic nerves continue into visual tracts. The optic nerve is connected with the nuclei of the diencephalon, and through them - with the cerebral cortex.

Each optic nerve contains a collection of all processes of nerve cells in the retina of one eye. In the region of the chiasm, an incomplete intersection of fibers occurs, and each optic tract contains about 50% of the fibers of the opposite side and the same number of fibers of its own side.

Central department

The central part 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 causes, the ability to control the curvature of the lens surface weakens.

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

farsightedness- focusing the image behind the retina; occurs due to a decrease in the bulge of the lens. Andcelebrate with glasseswith convex lenses.

There are two ways to conduct sounds:

air conduction: through the external auditory meatus, the tympanic membrane and the ossicular chain;
tissue conductivity b: through the tissues of the skull.

The function of the auditory analyzer: the perception and analysis of sound stimuli.

Peripheral: auditory receptors in the inner ear cavity.

Conduction department: auditory nerve.

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

Rice. Temporal bone Fig. The location of the organ of hearing 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 related anatomically and functionally.

outer ear consists of the external auditory meatus and the auricle.

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

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

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

Rice. Departments of the ear

OUTER EAR

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

Auricle made up of three tissues:

a thin plate of hyaline cartilage, covered on both sides with a 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 a significant amount in the lower part of the auricle - earlobe.

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

The auricle is designed in such a way as to concentrate sound vibrations as much as possible and direct them to the external auditory opening.

The shape, size, setting of the auricle and the size of the ear lobule are individual for each person.

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

Rice. Darwin's tubercle

External auditory pass is an S-shaped tube about 3 cm long and 0.7 cm in diameter, which opens from the outside with the auditory opening and is separated from the middle ear cavity tympanic membrane.

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

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

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

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

Sulfur is made up of proteins, fats, fatty acids and mineral salts. Some proteins are immunoglobulins that determine the protective function. In addition, sulfur contains dead cells, sebum, dust and other impurities.

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 to the outside during chewing and speech. In addition, the skin of the ear canal is constantly renewed and grows outward from the ear canal, carrying sulfur with it.

Interior bone department The external auditory meatus is a canal of the temporal bone ending in the tympanic membrane. In the middle of the bone section there is a narrowing of the auditory meatus - the isthmus, behind which there is a wider area.

The skin of the bone section is thin, does not contain hair follicles and glands, and passes to the eardrum, forming its outer layer.

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

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

The tympanic membrane is laid and develops along with the organs of the outer ear.

MIDDLE EAR

The middle ear is lined with mucous membrane and filled with air. tympanic cavity(volume approx. 1 withm3 cm3), three auditory ossicles and auditory (eustachian) tube.

Rice. Middle ear

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

In the septum that separates 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 stirrup;
round window: located in bottom of partition, leads to the beginning of the cochlea; closed by the secondary tympanic membrane.

There are three auditory ossicles in the tympanic cavity: hammer, anvil and stirrup (= stirrup). The auditory ossicles are small. Connecting with each other, they form a chain that stretches from the eardrum to the foramen ovale. All the bones are interconnected with the help of joints and are covered with a mucous membrane.

Hammer the handle is fused with the tympanic membrane, and the head is connected with the joint to anvil, which in turn is movably connected to stirrup. The base of the stirrup closes the oval window of the vestibule.

The muscles of the tympanic cavity (tensor tympanic membrane and stirrup) 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 is 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, consists of ciliated epithelium with the movement of cilia from the tympanic cavity to the nasopharynx.

Eustachian tube functions:

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

INTERNAL 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.

threshold- cavity small size and irregular shape, on the outer wall of which there are two windows (round and oval), leading to the tympanic cavity. The anterior part of the vestibule communicates with the cochlea via the scala vestibulum. The back part contains two depressions for the sacs of the vestibular apparatus.

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

Rice. The structure of the cochlea: 1 - basement membrane; 2 - organ of Corti; 3 - Reisner's membrane; 4 - staircase of the vestibule; 5 - spiral ganglion; 6 - drum stairs; 7 - vestibulo-coil nerve; 8 - spindle.

Semicircular canals- bone formations located in three mutually perpendicular planes. Each channel has an extended stem (ampulla).

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 vestibuli and the scala tympani. The cochlear duct contains auditory receptorsspiral, or Corti, organ;
three semicircular canals and two pouches located in the vestibule, which play the role of the vestibular apparatus.

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

organ of corti

On the plate of the cochlear duct, which is a continuation of the bone spiral plate, is Corti's (spiral) organ.

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

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

Rice. Organ of Corti

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

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

Rice. hair cells

CONDUCTION DEPARTMENT

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

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

In the pons, part of the nerve fibers through the chiasma passes to the opposite side and goes to the quadrigemina 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.

Primary auditory centers are used for the perception of auditory sensations, secondary - for their processing (understanding of speech and sounds, perception of music).

Rice. auditory analyzer

The facial nerve passes along with the auditory nerve to 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 facial muscles.

Physiology of hearing

The auditory 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 the receptors of the organ of Corti.

SOUND PRODUCTION

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 the leading nerve pathways, to the sound-receiving apparatus. The auricle, due to its shape, concentrates sound energy and directs it towards the external auditory meatus, which conducts sound vibrations to the eardrum.

Upon reaching the eardrum, sound waves cause it to vibrate. These vibrations of the tympanic membrane are transmitted to the malleus, through the joint - to the anvil, through the joint - to the stirrup, which closes the window of the vestibule (foramen ovale). Depending on the phase of sound vibrations, the base of the stirrup either squeezes into the labyrinth or stretches out of it. These movements of the stirrup cause fluctuations in the perilymph (see Fig.), 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 hanging over them. In this case, stretching or compression 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, the impulses pass along the corresponding leading paths to the auditory centers in the temporal parts of the cerebral cortex. Here nervous excitement turns into a sensation of sound.

Rice. Way sound signal : auricle - external auditory canal - tympanic membrane - hammer - anvil - stem - oval window - vestibule of the inner ear - vestibule ladder - basement membrane - hair cells of the organ of Corti. The 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 the sounds of the external environment with an oscillation frequency of 16 to 20,000 Hz (1 Hz = 1 oscillation in 1 s).

High-frequency sounds are perceived by the lower part of the curl, and low-frequency sounds are perceived by its top.

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

Ototopic- withThe ability to locate the source of a sound when 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: it enters 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.

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