Diagram of the structure of the peripheral part of the auditory analyzer. How does a hearing analyzer work?

14.3. Hearing analyzer

The outer ear consists of the pinna and the external auditory canal.

The basis of the auricle is elastic cartilage, supplemented skin fold- lobe filled with adipose tissue. The earlobe of a newborn is flattened, its cartilage is soft, the skin is thin, and the ear lobe is small. The auricle grows most rapidly during the first two years and after 10 years. It grows in length faster than in width. The free edge of the shell is folded inward in the shape of a curl, and an antihelix rises from its bottom. Medial to the latter is the cavity of the concha, in the depth of which there is the opening of the external auditory canal. In front of it is the tragus, behind it is the antitragus.

The external auditory canal is 24 mm long and ends at the eardrum. The first third of the auditory canal is a cartilaginous continuation of the concha, the remaining two thirds are bone and are located in the pyramid of the temporal bone. External auditory canal

in a newborn it is narrow and long (15 mm), steeply curved, narrowed, its medial and lateral sections are expanded. The walls of the external auditory canal are cartilaginous, with the exception of the tympanic ring. The length of the ear canal in a 1 year old child is 20 mm, and in a 5 year old child it is 22 mm. The auditory canal is lined with skin with thin fibers and modified sweat glands that secrete earwax. All this protects the eardrum from adverse environmental influences. The eardrum separates the outer ear from the middle ear. It consists of collagen fibers, covered on the outside by the epidermis, and on the inside by the mucous membrane. The eardrum in a newborn is well developed. Its height is 9 mm, width is 8 mm, like that of an adult, and forms an angle of 35-40°.

The middle ear consists of tympanic cavity, auditory ossicles and the auditory tube.

On the front wall of the tympanic cavity there is an opening in the auditory tube, through which it is filled with air. On the posterior wall of the cavity, the cells of the mastoid process open, and on the medial wall there are the window of the vestibule and the window of the cochlea, which lead to the inner ear. The tympanic cavity in a newborn is the same in size as in an adult. The mucous membrane is thickened, and therefore the tympanic cavity is filled with fluid. As breathing begins, it passes through the auditory tube into the pharynx and is swallowed. The walls of the tympanic cavity are thin, especially the upper one. Back wall has a wide opening leading into the mastoid cavity. Mastoid cells are absent in infants due to poor development of the mastoid process. The window of the cochlea is covered by a secondary tympanic membrane.

There are three auditory ossicles in the middle ear: the malleus, the incus and the stapes. The malleus is connected on one side to the eardrum, and on the other to the body of the incus. The long process of the latter articulates with the head of the stapes. The base of the stapes is adjacent to the window of the vestibule. The auditory ossicles of a newborn have dimensions close to those of an adult. All three bones connect the eardrum to the inner ear.

The auditory tube is a long (3.5 cm) and narrow (2 mm) cartilaginous canal that passes into the bone canal from the side of the pyramid. The pipe serves to equalize the air pressure on the eardrum. The opening of the pipe in the pharynx is in a collapsed state and air enters the tympanic cavity only when swallowing or yawning.

The auditory tube in a newborn is straight, wide and short, 17-18 mm long. During the first year of life it grows slowly (20 mm), in the second year it grows faster (30 mm). At 5 years old, its length is 35 mm, in an adult it is 35-38 mm. The lumen of the auditory tube narrows from 2.5 mm at 6 months to 2 mm at 2 years and 1-2 mm at 6 years.

The inner ear, or labyrinth, has double walls: the membranous labyrinth is inserted into the bone labyrinth. Between them there is a clear liquid - perilymph, and inside the membranous - endolymph.

The bony labyrinth consists of the vestibule, cochlea and three semicircular canals. The vestibule is an oval cavity connected to the tympanic cavity by a septum with two windows: oval (window of the vestibule) and round (window of the cochlea). The openings of the three semicircular canals and the spiral canal of the cochlea open into the vestibule. The structure of the semicircular canals will be discussed when describing the vestibular analyzer. The bony cochlea is a spiral canal that has two and a half turns around the cochlear shaft. A bony spiral plate extends from the rod, not reaching outer wall channel. From the free end of the spiral plate to the opposite wall of the cochlea, two membranes are stretched - spiral and vestibular, which limit the cochlear duct. The cochlear duct divides the cochlea into two parts, or scalae. The upper part, or scala vestibule, starts from oval window vestibule and goes to the top of the cochlea, where through a small opening it communicates with the lower canal, or scala tympani. It extends from the apex of the cochlea to the round fenestra of the cochlea. The vestibular and tympanic scalae are filled with perilymph, and the lumen of the cochlear duct is filled with endolymph. The inner ear of a newborn is well developed, its size is close to that of an adult. Bone walls semicircular canals are thin, gradually thicken due to ossification in the pyramid temporal bone.

On the spiral membrane lies a spiral organ consisting of supporting and receptor cells. On the cylindrical supporting cells lie receptor hair cells, which have outgrowths on their upper part, represented by large microvilli (stereocilia). Hair cells are either external, arranged in three rows, or internal, forming only one row. Between the outer and inner hair cells lies the tunnel of Corti, lined with columnar cells.

The cilia of the outer and inner hair cells come into contact with the tectorial membrane. This membrane is a homogeneous jelly-like mass attached to epithelial cells. The spiral membrane is unequal in width: in humans, near the oval window, its width is 0.04 mm, and then towards the apex of the cochlea, gradually expanding, it reaches 0.5 mm at the end. In the basal part of the spiral organ there are receptor cells that perceive higher frequencies, and in the apical part (at the top of the cochlea) there are cells that perceive only low frequencies.

The basal parts of the receptor cells contact the nerve fibers, which pass through the basement membrane and then exit into the spiral lamina canal. Next they go to the neurons of the spiral ganglion, which lies in the bony cochlea, where the conductive section of the auditory analyzer begins. The axons of the neurons of the spiral ganglion form fibers of the auditory nerve, which enters the brain between the inferior cerebellar peduncles and the pons and is directed into the pontine tegmentum, where the first crossover of the fibers takes place and the lateral lemniscus is formed. Some of its fibers end on the cells of the inferior colliculus, where the primary auditory center. Other fibers of the lateral lemniscus, as part of the handle of the inferior colliculus, approach the medial geniculate body. The processes of the cells of the latter form the auditory radiation, ending in the cortex of the superior temporal gyrus (cortical section of the auditory analyzer).

Mechanism of sound formation

As a result of the occurrence of electrical potentials, the auditory nerve fibers are excited, which are characterized by spontaneous activity even in silence (100 impulses/s). During sound, the frequency of impulses in the fibers increases throughout the entire duration of the stimulus. For each nerve fiber there is an optimal sound frequency that gives the highest discharge frequency and minimum response threshold. This optimal frequency is determined by the location on the basilar membrane where the receptors associated with a given fiber are located. Thus, the fibers of the auditory nerve are characterized by frequency selectivity, due to the excitation of different cells of the spiral organ. When the spiral organ is damaged, high tones fall out at the base, and low tones fall out at the apex. The destruction of the middle curl leads to the loss of tones in the middle frequency range.

There are two mechanisms for pitch discrimination: spatial and temporal encoding. Spatial coding is based on the unequal arrangement of excited receptor cells on the main membrane. At low and medium tones, time coding is also carried out. In this case, information is transmitted to certain groups of auditory nerve fibers; the frequency corresponds to the frequency of sound vibrations perceived by the cochlea.

All auditory neurons are characterized by the presence of frequency threshold indicators. These indicators reflect the dependence of the threshold sound required to excite a cell on its frequency. On both sides of the optimal frequency, the neuron response threshold increases, i.e. the neuron turns out to be tuned to sounds of only a certain frequency.

All this confirmed the hypothesis of G. Helmholtz (1863) about the mechanism for distinguishing sounds in the organ of Corti by their height. According to this hypothesis, the transverse fibers of the main membrane are short in its narrow part - at the base of the cochlea and 3-4 times longer in its wide part - at the apex. They are tuned like the strings of a musical instrument. Vibration of individual groups of fibers causes irritation of the corresponding receptor cells in the corresponding sections of the main membrane. These assumptions of G. Helmholtz were confirmed and were partially modified and developed in the works of the American physiologist D. Bekesy (1968).

The intensity of a sound is encoded by the number of neurons firing. With weak stimuli, only a small number of the most sensitive neurons are involved in the reaction, and as the sound intensifies, more and more additional neurons are excited. This is due to the fact that the neurons of the auditory analyzer differ sharply from each other in terms of their excitation threshold. The threshold is different for internal and external cells (for internal cells it is much higher), therefore, depending on the strength of the sound, the ratio of the number of excited external and internal cells changes.

A person perceives sounds with a frequency of 16 to 20,000 Hz. This range corresponds to 10-11 octaves. The limits of hearing depend on age: the older a person is, the more often he does not hear high tones. Sound frequency discrimination is characterized by the minimum difference in frequency of two sounds that a person perceives. A person can notice a difference of 1-2 Hz.

Absolute hearing sensitivity is the minimum strength of sound heard by a person in half the cases of its sound. In the region from 1000 to 4000 Hz, human hearing has maximum sensitivity. Speech fields also lie in this zone. The upper limit of audibility occurs when an increase in the intensity of a sound of a constant frequency causes an unpleasant feeling of pressure and pain in the ear. The unit of sound loudness is bel. In everyday life, decibels are usually used as a unit of loudness, i.e. 0.1 bel. The maximum volume level when sound causes pain is 130-140 dB above the threshold of audibility.

If one or another sound affects the ear for a long time, then the sensitivity of hearing decreases, i.e. adaptation occurs. The adaptation mechanism is associated with the contraction of the muscles going to the eardrum and stapes (with their contraction, the intensity of the sound energy transmitted to the cochlea changes), and with the descending influence of the reticular formation of the midbrain.

The auditory analyzer has two symmetrical halves (binaural hearing), i.e. Humans are characterized by spatial hearing - the ability to determine the position of a sound source in space. The acuity of such hearing is great. A person can determine the location of a sound source with an accuracy of 1°. This is because if the sound source is away from the midline of the head, the sound wave arrives at one ear earlier and with greater force than at the other. In addition, at the level of the posterior colliculus, neurons were found that respond only to a certain direction of movement of the sound source in space.

Hearing in ontogenesis

Despite the early development of the auditory analyzer, the hearing organ in a newborn is not yet fully formed. He has relative deafness, which is associated with the structural features of the ear. The middle ear cavity in newborns is filled with amniotic fluid, which makes it difficult for the auditory ossicles to vibrate. The amniotic fluid gradually resolves, and air enters the ear cavity from the nasopharynx through the Eustachian tube.

Newborn reacts to loud sounds shuddering, cessation of crying, change in breathing. Children's hearing becomes quite clear by the end of the 2nd - beginning of the 3rd month. At the 2nd month of life, the child differentiates qualitatively different sounds, at 3-4 months he distinguishes pitches ranging from 1 to 4 octaves, at 4-5 months the sounds become conditioned stimuli, although conditioned food and defensive reflexes to sound stimuli are developed already from 3-5 weeks of age. By 1-2 years, children differentiate sounds, the difference between which is 1 tone, and by 4 years - even 3/4 and 1/2 tones.

Hearing acuity is determined by the lowest sound intensity that can cause a sound sensation (hearing threshold). For an adult, the hearing threshold is in the range of 10-12 dB, for children 6-9 years old - 17-24 dB, 10-12 years old - 14-19 dB. The greatest acuity of sound is achieved in middle and high school age. Children perceive low tones better than high ones. In the development of hearing in children great importance has contact with adults. Listening to music and learning to play musical instruments develop children's hearing.

Introduction

Conclusion

Bibliography

Introduction

The society in which we live is Information society, where the main factor of production is knowledge, the main product of production is services, and characteristic features society are computerization, as well as a sharp increase in creativity in work. The role of connections with other countries is increasing, and the process of globalization is taking place in all spheres of society.

A key role in communication between states is played by professions related to foreign languages, linguistics, and social sciences. There is an increasing need to study speech recognition systems for automated translation, which will help increase labor productivity in areas of the economy related to intercultural communication. Therefore, it is important to study the physiology and mechanisms of functioning of the auditory analyzer as a means of perceiving and transmitting speech to the corresponding part of the brain for subsequent processing and synthesis of new speech units.

The auditory analyzer is a set of mechanical, receptor and nervous structures, the activity of which ensures the perception of sound vibrations by humans and animals. From an anatomical point of view auditory system can be divided into the outer, middle and inner ear, auditory nerve and central auditory pathways. From the point of view of the processes that ultimately lead to the perception of hearing, the auditory system is divided into sound-conducting and sound-perceiving.

Under different conditions environment Under the influence of many factors, the sensitivity of the auditory analyzer may change. To study these factors there are various methods hearing research.

auditory analyzer physiology sensitivity

1. The importance of studying human analyzers from the point of view of modern information technologies

Already several decades ago, people made attempts to create speech synthesis and recognition systems in modern information technology. Of course, all these attempts began with a study of the anatomy and principles of speech, as well as auditory organs human, in the hope of simulating them using a computer and special electronic devices.

What are the features of the human auditory analyzer? The auditory analyzer captures the shape of the sound wave, the frequency spectrum of pure tones and noises, carries out, within certain limits, the analysis and synthesis of the frequency components of sound stimuli, detects and identifies sounds in a wide range of intensities and frequencies. The auditory analyzer allows you to differentiate sound stimuli and determine the direction of the sound, as well as the distance of its source. The ears sense vibrations in the air and convert them into electrical signals that travel to the brain. As a result of processing by the human brain, these signals turn into images. The creation of such information processing algorithms for computer technology is a scientific problem, the solution of which is necessary to develop the most error-free speech recognition systems.

Many users dictate the text of documents using speech recognition programs. This opportunity is relevant, for example, for doctors conducting an examination (during which their hands are usually busy) and at the same time recording its results. PC users can use speech recognition programs to enter commands, meaning the spoken word will be perceived by the system as a mouse click. The user commands: “Open file”, “Send mail” or “New window”, and the computer performs the corresponding actions. This is especially true for people with disabilities - instead of a mouse and keyboard, they will be able to control the computer using their voice.

Studying the inner ear helps researchers understand the mechanisms by which humans are able to recognize speech, although it is not that simple. Man “spies” on many inventions from nature, and such attempts are also made by specialists in the field of speech synthesis and recognition.

2. Types of human analyzers and their brief characteristics

Analyzers (from the Greek analysis - decomposition, dismemberment) - a system of sensitive nervous formations that carry out the analysis and synthesis of external and internal environment body. The term was introduced into the neurological literature by I.P. Pavlov, according to whose ideas each analyzer consists of specific perceptive formations (receptors, sensory organs) that make up the peripheral part of the analyzer, the corresponding nerves connecting these receptors with different floors of the central nervous system (conductive part), and the brain end, which is represented in higher animals in the cortex of the large cerebral hemispheres.

Depending on the receptor function, analyzers of the external and internal environment are distinguished. The first receptors are directed to the external environment and are adapted to analyze phenomena occurring in the surrounding world. Such analyzers include a visual analyzer, a hearing analyzer, a skin analyzer, an olfactory analyzer, and a gustatory analyzer. Analyzers of the internal environment are afferent nervous devices, the receptor apparatus of which is located in internal organs and are adapted to analyze what is happening in the body itself. Such analyzers also include a motor analyzer (its receptor apparatus is represented by muscle spindles and Golgi receptors), which provides the possibility of precise control of the musculoskeletal system. Another internal analyzer, the vestibular one, closely interacts with the movement analyzer, also plays a significant role in the mechanisms of statokinetic coordination. The human motor analyzer also includes a special section that ensures the transmission of signals from the receptors of the speech organs to the higher levels of the central nervous system. Due to the importance of this section in the activity of the human brain, it is sometimes considered a “speech-motor analyzer.”

The receptor apparatus of each analyzer is adapted to transformation certain type energy into nervous excitement. Thus, sound receptors selectively react to sound stimulation, light - to light, taste - to chemical, skin - to tactile-temperature, etc. The specialization of receptors ensures the analysis of external world phenomena into their individual elements already at the level of the peripheral part of the analyzer.

Biological role analyzers is that they are specialized tracking systems that inform the body about all events occurring in the environment and within it. From the huge flow of signals continuously entering the brain through external and internal analyzers, that useful information is selected that turns out to be essential in the processes of self-regulation (maintaining an optimal, constant level of functioning of the body) and active behavior animals in the environment. Experiments show that the complex analytical and synthetic activity of the brain, determined by factors of the external and internal environment, is carried out according to the polyanalyzer principle. This means that the entire complex neurodynamics of cortical processes, which forms the integral activity of the brain, consists of a complex interaction of analyzers. But this concerns a different topic. Let's move directly to the auditory analyzer and look at it in more detail.

3. Auditory analyzer as a means of human perception of sound information

3.1 Physiology of the auditory analyzer

The peripheral section of the auditory analyzer (the auditory analyzer with the organ of balance - the ear (auris)) is a very complex sensory organ. The endings of its nerve are located deep in the ear, due to which they are protected from the action of all kinds of extraneous irritants, but at the same time are easily accessible to sound stimulation. The organ of hearing contains three types of receptors:

a) receptors that perceive sound vibrations (vibrations of air waves), which we perceive as sound;

b) receptors that enable us to determine the position of our body in space;

c) receptors that perceive changes in the direction and speed of movement.

The ear is usually divided into three sections: the outer, middle and inner ear.

Outer earconsists of the auricle and the external auditory canal. The auricle is built of elastic elastic cartilage, covered with a thin, inactive layer of skin. She is a collector of sound waves; in humans it is motionless and does not play an important role, unlike animals; even in its complete absence, no noticeable hearing impairment is observed.

The external auditory canal is a slightly curved canal about 2.5 cm in length. This canal is lined with skin with small hairs and contains special glands, similar to large apocrine glands of the skin, secreting earwax, which, together with the hairs, protects the outer ear from clogging with dust. It consists of an outer section, the cartilaginous external auditory canal, and an internal section, the bony auditory canal, located in the temporal bone. Its inner end is closed by a thin elastic eardrum, which is a continuation of the skin of the external auditory canal and separates it from the cavity of the middle ear. The outer ear plays only a supporting role in the organ of hearing, participating in the collection and conduction of sounds.

Middle ear, or tympanic cavity (Fig. 1), is located inside the temporal bone between the outer ear canal, from which it is separated by the eardrum, and the inner ear; it is a very small, irregularly shaped cavity with a capacity of up to 0.75 ml, which communicates with the accessory cavities - the cells of the mastoid process and the pharyngeal cavity (see below).

Rice. 1. Sectional view of the hearing organ. 1 - geniculate ganglion of the facial nerve; 2 - facial nerve; 3 - hammer; 4 - superior semicircular canal; 5 - posterior semicircular canal; 6 - anvil; 7 - bony part of the external auditory canal; 8 - cartilaginous part external auditory canal; 9 - eardrum; 10 - bone part of the auditory tube; 11 - cartilaginous part of the auditory tube; 12 - greater superficial petrosal nerve; 13 - top of the pyramid.

On medial wall the tympanic cavity, facing the inner ear, has two openings: the oval window of the vestibule and the round window of the cochlea; the first is covered by the stirrup plate. The tympanic cavity communicates with the auditory (Eustachian) tube (tuba auditiva) through a small (4 cm long) upper section pharynx - nasopharynx. The hole of the pipe opens on the side wall of the pharynx and in this way communicates with the outside air. Every time the auditory tube opens (which happens with every swallowing movement), the air in the tympanic cavity is renewed. Thanks to it, the pressure on the eardrum from the side of the tympanic cavity is always maintained at the level of outside air pressure, and thus, the outside and inside of the eardrum is exposed to the same atmospheric pressure.

This equalization of pressure on both sides of the eardrum has a very important, since normal fluctuations are possible only when the pressure of the outside air is equal to the pressure in the cavity of the middle ear. When there is a difference between atmospheric air pressure and the pressure of the tympanic cavity, hearing acuity is impaired. Thus, the auditory tube is a kind of safety valve that equalizes the pressure in the middle ear.

The walls of the tympanic cavity and especially the auditory tube are lined with epithelium, and the mucous tubes are lined with ciliated epithelium; the vibration of its hairs is directed towards the pharynx.

The pharyngeal end of the auditory tube is rich in mucous glands and lymph nodes.

On the lateral side of the cavity is the eardrum. The eardrum (membrana tympani) (Fig. 2) perceives sound vibrations in the air and transmits them to the sound conducting system of the middle ear. It has the shape of a circle or ellipse with a diameter of 9 and 11 mm and consists of an elastic connective tissue, the fibers of which are arranged radially on the outer surface, and circularly on the inner surface; its thickness is only 0.1 mm; it is stretched somewhat obliquely: from top to bottom and from back to front, it is slightly concave inward, since the mentioned muscle stretches from the walls of the tympanic cavity to the handle of the malleus, stretching the eardrum (it pulls the membrane inward). The chain of auditory ossicles serves to transmit air vibrations from the eardrum to the fluid filling the inner ear. The eardrum is not stretched very much and does not emit its own tone, but transmits only the sounds it receives. sound waves. Due to the fact that vibrations of the eardrum decay very quickly, it is an excellent transmitter of pressure and almost does not distort the shape of the sound wave. On the outside, the eardrum is covered with thinned skin, and on the surface facing the tympanic cavity - with a mucous membrane lined with flat multilayered epithelium.

Between the eardrum and the oval window there is a system of small auditory ossicles that transmit vibrations of the eardrum to the inner ear: the malleus, incus and stapes, connected by joints and ligaments that are driven by two small muscles. The hammer is incremented to inner surface the eardrum with its handle, and the head is articulated with the anvil. The anvil, with one of its processes, is connected to the stirrup, which is located horizontally and with its wide base (plate) inserted into the oval window, tightly adjacent to its membrane.

Rice. 2. Eardrum and auditory ossicles with inside. 1 - head of the hammer; 2 - its upper ligament; 3 - cave of the tympanic cavity; 4 - anvil; 5 - a bunch of it; 6 - drum string; 7 - pyramidal elevation; 8 - stirrup; 9 - hammer handle; 10 - eardrum; eleven - Eustachian tube; 12 - partition between the half-channels for the pipe and for the muscle; 13 - muscle that strains the tympanic membrane; 14 - anterior process of the malleus

The muscles of the tympanic cavity deserve a lot of attention. One of them is m. tensor tympani - attached to the neck of the malleus. When it contracts, the articulation between the malleus and the incus is fixed and the tension of the eardrum increases, which occurs with strong sound vibrations. At the same time, the base of the stapes is slightly pressed into the oval window.

The second muscle is m. stapedius (the smallest striated muscle in the human body) - attaches to the head of the stapes. When this muscle contracts, the articulation between the incus and the stapes is pulled downward and limits the movement of the stapes in the oval window.

Inner ear.The inner ear is the most important and most complex arranged part hearing aid called the labyrinth. The labyrinth of the inner ear is located deep in the pyramid of the temporal bone, as if in a bone case between the middle ear and the internal auditory canal. The size of the bony ear labyrinth along its long axis does not exceed 2 cm. It is separated from the middle ear by the oval and round windows. The opening of the internal auditory canal on the surface of the pyramid of the temporal bone, through which the auditory nerve exits the labyrinth, is closed by a thin bone plate with small holes for the auditory nerve fibers to exit the inner ear. Inside the bone labyrinth there is a closed connective tissue membranous labyrinth, which exactly repeats the shape of the bone labyrinth, but is somewhat smaller in size. The narrow space between the bony and membranous labyrinths is filled with a fluid similar in composition to lymph and called perilimph. The entire internal cavity of the membranous labyrinth is also filled with a fluid called endolymph. The membranous labyrinth is connected in many places to the walls of the bony labyrinth by dense cords running through the perilymphatic space. Thanks to this arrangement, the membranous labyrinth is suspended inside the bony labyrinth, just as the brain is suspended (inside the skull on its meninges.

The labyrinth (Fig. 3 and 4) consists of three sections: the vestibule of the labyrinth, the semicircular canals and the cochlea.

Rice. 3. Diagram of the relationship of the membranous labyrinth to the bony labyrinth. 1 - duct connecting the utricle with the sac; 2 - superior membranous ampulla; 3 - endolymphatic duct; 4 - endolymphatic sac; 5 - translymphatic space; 6 - pyramid of the temporal bone: 7 - apex of the membranous cochlear duct; 8 - communication between both staircases (helicotrema); 9 - cochlear membranous passage; 10 - staircase vestibule; 11 - drum ladder; 12 - bag; 13 - connecting stroke; 14 - perilymphatic duct; 15 - round window of the cochlea; 16 - oval window of the vestibule; 17 - tympanic cavity; 18 - blind end of the cochlear duct; 19 - posterior membranous ampulla; 20 - utricle; 21 - semicircular canal; 22 - upper semicircular course

Rice. 4. Transverse section through the cochlea. 1 - staircase vestibule; 2 - Reissner's membrane; 3 - integumentary membrane; 4 - cochlear canal, in which the organ of Corti is located (between the integumentary and main membranes); 5 and 16 - auditory cells with cilia; 6 - supporting cells; 7 - spiral ligament; 8 and 14 - bone snails; 9 - supporting cell; 10 and 15 - special supporting cells (the so-called Corti cells - pillars); 11 - scala tympani; 12 - main membrane; 13 - nerve cells of the spiral cochlear ganglion

The membranous vestibule (vestibulum) is a small oval cavity occupying middle part labyrinth and consisting of two vesicles-sacs connected to each other by a narrow tubule; one of them - the posterior one, the so-called utricle (utriculus), communicates with the membranous semicircular canals with five openings, and the anterior sac (sacculus) - with membranous snail. Each of the sacs of the vestibule apparatus is filled with endolymph. The walls of the sacs are lined flat epithelium, with the exception of one area - the so-called spot (macula), where there is a cylindrical epithelium containing supporting and hair cells bearing thin processes on their surface facing the cavity of the sac. Higher animals have small lime crystals (otoliths), glued together into one lump along with neuronal hairs. epithelial cells, in which the nerve fibers of the vestibular nerve (ramus vestibularis - branch of the auditory nerve) end.

Behind the vestibule there are three mutually perpendicular semicircular canals (canales semicirculares) - one in the horizontal plane and two in the vertical. The semicircular canals are very narrow tubes filled with endolymph. Each of the canals forms an extension at one of its ends - an ampulla, where the endings of the vestibular nerve are located, distributed in the cells of the sensitive epithelium, concentrated in the so-called auditory crest (crista acustica). The cells of the sensitive epithelium of the auditory comb are very similar to those present in the speck - on the surface facing the cavity of the ampulla, they bear hairs that are glued together and form a kind of brush (cupula). The free surface of the brush reaches the opposite (upper) wall of the canal, leaving an insignificant lumen of its cavity free, preventing the movement of endolymph.

In front of the vestibule is the cochlea, which is a membranous, spirally convoluted canal, also located inside the bone. The cochlear spiral in humans makes 2 3/4revolution around the central bone axis and ends blind. The bony axis of the cochlea with its apex faces the middle ear, and its base closes the internal auditory canal.

Into the cavity of the spiral canal of the cochlea along its entire length, a spiral bone plate also extends and protrudes from the bony axis - a septum that divides the spiral cavity of the cochlea into two passages: the upper one, communicating with the vestibule of the labyrinth, the so-called staircase of the vestibule (scala vestibuli), and the lower one, abutting one end into the membrane of the round window of the tympanic cavity and therefore called the scala tympani (scala tympani). These passages are called staircases because, curling in a spiral, they resemble a staircase with an obliquely rising strip, but without steps. At the end of the cochlea, both passages are connected by a hole about 0.03 mm in diameter.

This longitudinal bone plate blocking the cavity of the cochlea, extending from the concave wall, does not reach the opposite side, and its continuation is a connective tissue membranous spiral plate, called the main membrane, or the main membrane (membrana basilaris), which is already closely adjacent to the convex opposite wall along the the entire length common cavity snails

Another membrane (Reisner’s) extends from the edge of the bone plate at an angle above the main one, which limits a small middle passage between the first two passages (scales). This passage is called the cochlear canal (ductus cochlearis) and communicates with the vestibule sac; it is the organ of hearing in the proper sense of the word. The canal of the cochlea in a cross section has the shape of a triangle and, in turn, is divided (but not completely) into two floors by a third membrane - the integumentary membrane (membrana tectoria), which apparently plays a large role in the process of perception of sensations. In the lower floor of this last canal, on the main membrane in the form of a protrusion of the neuroepithelium, there is a very complex device, the actual perceptive apparatus of the auditory analyzer - the spiral (organon spirale Cortii) (Fig. 5), washed together with the main membrane by the intralabyrinthine fluid and playing in relation to to hearing the same role as the retina in relation to vision.

Rice. 5. Microscopic structure organ of Corti. 1 - main membrane; 2 - cover membrane; 3 - auditory cells; 4 - auditory ganglion cells

The spiral organ consists of numerous diverse supporting and epithelial cells located on the main membrane. The elongated cells are arranged in two rows and are called pillars of Corti. The cells of both rows are slightly inclined towards each other and form up to 4000 arcs of Corti throughout the cochlea. In this case, a so-called internal tunnel is formed in the cochlear canal, filled with intercellular substance. On the inner surface of the Corti columns there is a number of cylindrical epithelial cells, on the free surface of which there are 15-20 hairs - these are sensitive, perceptive, so-called hair cells. Thin and long fibers - auditory hairs, sticking together, form delicate brushes on each such cell. TO outside These auditory cells are adjacent to the supporting Deiters cells. Thus, the hair cells are anchored to the main membrane. Thin nerve fibers without pulp approach them and form an extremely delicate fibrillar network in them. The auditory nerve (its branch - ramus cochlearis) penetrates the middle of the cochlea and runs along its axis, giving off numerous branches. Here, each pulpy nerve fiber loses its myelin and becomes a nerve cell, which, like the cells of the spiral ganglia, has a connective tissue sheath and glial meningeal cells. The whole amount of these nerve cells as a whole and forms a spiral ganglion (ganglion spirale), occupying the entire periphery of the cochlear axis. From this nerve ganglion, nerve fibers are already sent to the perceptive apparatus - the spiral organ.

The main membrane itself, on which the spiral organ is located, consists of the thinnest, dense and tightly stretched fibers (“strings”) (about 30,000), which, starting from the base of the cochlea (near the oval window), gradually lengthen to its upper curl, ranging from 50 to 500 ?(more precisely, from 0.04125 to 0.495 mm), i.e. short near the oval window, they become increasingly longer towards the apex of the cochlea, increasing by about 10-12 times. The length of the main membrane from the base to the apex of the cochlea is approximately 33.5 mm.

Helmholtz, who created the theory of hearing at the end of the last century, compared the main membrane of the cochlea with its fibers of different lengths to a musical instrument - a harp, only in this living harp it is tense great amount"strings".

The perceiving apparatus of auditory stimuli is the spiral (Corti) organ of the cochlea. The vestibule and semicircular canals play the role of balance organs. True, the perception of the position and movement of the body in space depends on the joint function of many senses: vision, touch, muscle sense, etc., i.e. reflex activity, necessary to maintain balance, is provided by impulses in various organs. But the main role in this belongs to the vestibule and semicircular canals.

3.2 Sensitivity of the hearing analyzer

The human ear perceives air vibrations from 16 to 20,000 Hz as sound. The upper limit of perceived sounds depends on age: the older the person, the lower it is; Often older people cannot hear high tones, such as the sound made by a cricket. In many animals upper limit lies above; in dogs, for example, it is possible to form a whole series conditioned reflexes on not audible to humans sounds.

With fluctuations up to 300 Hz and above 3000 Hz, the sensitivity decreases sharply: for example, at 20 Hz, as well as at 20,000 Hz. With age, the sensitivity of the auditory analyzer, as a rule, decreases significantly, but mainly to high-frequency sounds, while to low-frequency sounds (up to 1000 vibrations per second) it remains almost unchanged until old age.

This means that to improve the quality of speech recognition, computer systems can exclude from analysis frequencies that lie outside the range of 300-3000 Hz or even outside the range of 300-2400 Hz.

In conditions of complete silence, hearing sensitivity increases. If a tone of a certain pitch and constant intensity begins to sound, then, due to adaptation to it, the sensation of loudness decreases, first quickly, and then more and more slowly. However, although to a lesser extent, sensitivity to sounds that are more or less close in vibration frequency to the sounding tone decreases. However, adaptation usually does not extend to the entire range of perceived sounds. After the sound stops, due to adaptation to silence, the previous level of sensitivity is restored within 10-15 seconds.

Adaptation partly depends on the peripheral part of the analyzer, namely on changes in both the amplifying function of the sound apparatus and the excitability of the hair cells of the organ of Corti. The central section of the analyzer also takes part in adaptation phenomena, as evidenced by the fact that when sound affects only one ear, shifts in sensitivity are observed in both ears.

Sensitivity also changes with the simultaneous action of two tones of different heights. In the latter case, a weak sound is drowned out by a stronger one, mainly because the focus of excitation, which arises in the cortex under the influence of a strong sound, reduces, due to negative induction, the excitability of other parts of the cortical section of the same analyzer.

Prolonged exposure to strong sounds can cause prohibitive inhibition of cortical cells. As a result, the sensitivity of the auditory analyzer sharply decreases. This condition persists for some time after the irritation has stopped.

Conclusion

The complex structure of the auditory analyzer system is determined by a multi-stage algorithm for signal transmission to the temporal region of the brain. The outer and middle ears transmit sound vibrations to the cochlea, located in the inner ear. Sensitive hairs located in the cochlea convert vibrations into electrical signals that travel along nerves to the auditory area of the brain.

When considering the functioning of an auditory analyzer for further application of knowledge when creating speech recognition programs, one should also take into account the sensitivity limits of the hearing organ. The frequency range of sound vibrations perceived by humans is 16-20,000 Hz. However, the frequency range of speech is already 300-4000 Hz. Speech remains intelligible with further constriction frequency range up to 300-2400 Hz. This fact can be used in speech recognition systems to reduce the influence of interference.

Bibliography

1.P.A. Baranov, A.V. Vorontsov, S.V. Shevchenko. Social studies: a complete reference book. Moscow 2013

2.Great Soviet Encyclopedia, 3rd edition (1969-1978), volume 23.

.A.V. Frolov, G.V. Frolov. Speech synthesis and recognition. Modern solutions.

.Dushkov B.A., Korolev A.V., Smirnov B.A. encyclopedic Dictionary: Labor psychology, management, engineering psychology and ergonomics. Moscow, 2005

.Kucherov A.G. Anatomy, physiology and methods of studying the organ of hearing and balance. Moscow, 2002

.Stankov A.G. Human anatomy. Moscow, 1959

7.http://ioi-911. ucoz.ru/publ/1-1-0-47

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PHYSIOLOGY OF THE HEARING ANALYZER

(Auditory sensory system)

Lecture questions:

1. Structural and functional characteristics of the auditory analyzer:

a. Outer ear

b. Middle ear

c. Inner ear

2. Divisions of the auditory analyzer: peripheral, conductive, cortical.

3. Perception of height, sound intensity and sound source location:

a. Basic electrical phenomena in the cochlea

b. Perception of sounds of different pitches

c. Perception of sounds varying intensity

d. Identifying the sound source (binaural hearing)

e. Auditory adaptation

1. The auditory sensory system is the second most important distant human analyzer, plays important role specifically in humans in connection with the emergence of articulate speech.

Hearing analyzer function: transformation sound waves into the energy of nervous excitation and auditory sensation.

Like any analyzer, the auditory analyzer consists of a peripheral, conductive and cortical section.

PERIPHERAL DEPARTMENT

Converts the energy of sound waves into energy nervous excitation – receptor potential (RP). This department includes:

· inner ear (sound-receiving apparatus);

· middle ear (sound-conducting apparatus);

· outer ear (sound-collecting apparatus).

The components of this department are combined into the concept organ of hearing.

Functions of the organs of hearing

Outer ear:

a) collecting sound (auricle) and directing the sound wave into the external auditory canal;

b) conducting a sound wave through the ear canal to the eardrum;

c) mechanical protection and protection from environmental temperature influences of all other parts of the hearing organ.

Middle ear(sound-conducting section) is the tympanic cavity with 3 auditory ossicles: the malleus, the incus and the stapes.

The eardrum separates the external auditory canal from the tympanic cavity. The handle of the malleus is woven into the eardrum, its other end is articulated with the incus, which, in turn, is articulated with the stapes. The stapes is adjacent to the membrane of the oval window. The pressure in the tympanic cavity is equal to atmospheric pressure, which is very important for adequate perception of sounds. This function is performed by the Eustachian tube, which connects the middle ear cavity to the pharynx. When swallowing, the tube opens, resulting in ventilation of the tympanic cavity and equalization of the pressure in it with atmospheric pressure. If external pressure changes rapidly (rapid rise to altitude), and swallowing does not occur, then the pressure difference between atmospheric air and the air in the tympanic cavity leads to tension of the eardrum and the occurrence of unpleasant sensations (“stuck ears”), and a decrease in the perception of sounds.

The area of the eardrum (70 mm2) is significantly more area oval window (3.2 mm 2), due to which it occurs gain the pressure of sound waves on the membrane of the oval window is 25 times. Lever mechanism of bones reduces the amplitude of sound waves is 2 times, so the same amplification of sound waves occurs at the oval window of the tympanic cavity. Consequently, the middle ear amplifies sound by about 60-70 times, and if we take into account the amplifying effect of the outer ear, then this value increases by 180-200 times. In this regard, in case of strong sound vibrations, to prevent destructive action sound to the receptor apparatus of the inner ear, the middle ear reflexively turns on " defense mechanism" It consists of the following: in the middle ear there are 2 muscles, one of them stretches the eardrum, the other fixes the stapes. Under strong sound impacts, these muscles, when contracting, limit the amplitude of vibration of the eardrum and fix the stapes. This “quenches” the sound wave and protects overexcitement and destruction of phonoreceptors of the organ of Corti.

Inner ear: represented by the cochlea - a spirally twisted bone canal (2.5 turns in humans). This channel is divided along its entire length into three narrow parts (ladders) with two membranes: the main membrane and the vestibular membrane (Reisner).

On the main membrane there is a spiral organ - the organ of Corti (organ of Corti) - this is the actual sound-receiving apparatus with receptor cells - this is the peripheral section of the auditory analyzer.

The helicotrema (orifice) connects the superior and inferior canals at the apex of the cochlea. The middle channel is separate.

Above the organ of Corti is a tectorial membrane, one end of which is fixed and the other remains free. The hairs of the outer and inner hair cells of the organ of Corti come into contact with the tectorial membrane, which is accompanied by their excitation, i.e. the energy of sound vibrations is transformed into the energy of the excitation process.

Structure of the organ of Corti

The transformation process begins with sound waves entering the outer ear; they move the eardrum. Vibrations of the tympanic membrane through the system of auditory ossicles of the middle ear are transmitted to the membrane of the oval window, which causes vibrations of the perilymph of the scala vestibularis. These vibrations are transmitted through the helicotrema to the perilymph of the scala tympani and reach the round window, protruding it towards the middle ear (this prevents the sound wave from dying out when passing through the vestibular and tympanic canal of the cochlea). Vibrations of the perilymph are transmitted to the endolymph, which causes vibrations of the main membrane. The fibers of the basilar membrane begin to vibrate together with the receptor cells (outer and inner hair cells) of the organ of Corti. In this case, the phonoreceptor hairs come into contact with the tectorial membrane. The cilia of the hair cells are deformed, this causes the formation of a receptor potential, and on its basis an action potential (nerve impulse), which is carried along the auditory nerve and transmitted to the next section of the auditory analyzer.

CONDUCTING DEPARTMENT OF THE HEARING ANALYZER

Wiring department auditory analyzer presented auditory nerve. It is formed by the axons of neurons of the spiral ganglion (1st neuron of the pathway). The dendrites of these neurons innervate the hair cells of the organ of Corti (afferent link), the axons form the fibers of the auditory nerve. The auditory nerve fibers end on the neurons of the nuclei of the cochlear body (VIII pair of h.m.n.) (second neuron). Then, after partial crossing, the fibers auditory pathway go to the medial geniculate body of the thalamus, where switching occurs again (third neuron). From here the excitation enters the cortex ( temporal lobe, superior temporal gyrus, transverse gyri of Heschl) is the projection auditory cortex area.

CORTICAL DIVISION OF THE AUDITORY ANALYZER

Presented in temporal lobe cerebral cortex - superior temporal gyrus, transverse temporal gyri Geschlya. Cortical gnostic auditory zones are associated with this projection zone of the cortex - Wernicke's sensory speech area and praxial zone – Broca's speech motor center(inferior frontal gyrus). The cooperative activity of the three cortical zones ensures the development and function of speech.

The auditory sensory system has feedbacks, which provide regulation of the activity of all levels of the auditory analyzer with the participation descending paths, which start from the neurons of the “auditory” cortex and sequentially switch in the medial geniculate body of the thalamus, the inferior colliculus of the midbrain with the formation of tectospinal descending tracts and on the nuclei of the cochlear body of the medulla oblongata with the formation of vestibulospinal tracts. This ensures, in response to the action of a sound stimulus, the formation of a motor reaction: turning the head and eyes (and in animals, the ears) towards the stimulus, as well as increasing the tone of the flexor muscles (flexion of the limbs in the joints, i.e. readiness to jump or run ).

Auditory cortex

PHYSICAL CHARACTERISTICS OF SOUND WAVES THAT ARE PERCEIVED BY THE HEARING ORGAN

1. The first characteristic of sound waves is their frequency and amplitude.

The frequency of sound waves determines the pitch of the sound!

A person distinguishes sound waves with a frequency from 16 to 20,000 Hz (this corresponds to 10-11 octaves). Sounds whose frequency is below 20 Hz (infrasounds) and above 20,000 Hz (ultrasounds) by humans not felt!

Sound that consists of sinusoidal or harmonic vibrations is called tone(high frequency - high tone, low frequency - low tone). A sound consisting of unrelated frequencies is called noise.

2. The second characteristic of sound that the auditory sensory system distinguishes is its strength or intensity.

The strength of sound (its intensity) together with the frequency (tone of sound) is perceived as volume. The unit of loudness measurement is bel = lg I/I 0, but in practice it is more often used decibel (dB)(0.1 bel). A decibel is 0.1 decimal logarithm of the ratio of sound intensity to its threshold intensity: dB = 0.1 log I/I 0. The maximum volume level when sound causes pain is 130-140 dB.

The sensitivity of the auditory analyzer is determined by the minimum sound intensity that causes auditory sensations.

In the range of sound vibrations from 1000 to 3000 Hz, which corresponds to human speech, the ear has the greatest sensitivity. This set of frequencies is called speech zone(1000-3000 Hz). Absolute sound sensitivity in this range is 1*10 -12 W/m2. For sounds above 20,000 Hz and below 20 Hz, absolute hearing sensitivity decreases sharply - 1*10 -3 W/m2. In the speech range, sounds are perceived that have a pressure of less than 1/1000 of a bar (a bar is equal to 1/1,000,000 of normal atmospheric pressure). Based on this, in transmitting devices, in order to ensure adequate understanding of speech, information must be transmitted in the speech frequency range.

MECHANISM OF PERCEPTION OF HEIGHT (FREQUENCY), INTENSITY (STRENGTH) AND LOCALIZATION OF SOUND SOURCE (BINAURAL HEARING)

Perception of sound wave frequency

The auditory analyzer is a set of mechanical, receptor and neural structures that perceive and analyze sound vibrations. The peripheral section of the auditory analyzer is represented by the auditory organ, consisting of the outer, middle and inner ear. The outer ear consists of the pinna and the external auditory canal. The auricle of a newborn is flattened, its cartilage is soft, the skin is thin, and the earlobe is small. The auricle grows most rapidly during the first two years and after 10 years. It grows in length faster than in width. The eardrum separates the outer ear from the middle ear. The middle ear consists of the tympanic cavity, the auditory ossicles and the auditory tube.

The tympanic cavity in a newborn is the same in size as in an adult. In the middle ear there are three auditory ossicles: the malleus, the incus and the inner ear, or labyrinth, has double walls: the membranous labyrinth is inserted into the bone labyrinth. The bony labyrinth consists of the vestibule, cochlea and three semicircular canals. The cochlear duct divides the cochlea into two parts, or scalae. The inner ear of a newborn is well developed, its size is close to that of an adult. The basal parts of the receptor cells contact the nerve fibers, which pass through the basement membrane and then exit into the spiral lamina canal. Next they go to the neurons of the spiral ganglion, which lies in the bony cochlea, where the conductive section of the auditory analyzer begins. The axons of the neurons of the spiral ganglion form fibers of the auditory nerve, which enters the brain between the inferior cerebellar peduncles and the pons and is directed into the pontine tegmentum, where the first crossover of the fibers takes place and the lateral lemniscus is formed. Some of its fibers end on the cells of the inferior colliculus, where the primary auditory center is located. Other fibers of the lateral lemniscus, as part of the handle of the inferior colliculus, approach the medial geniculate body. The processes of the cells of the latter form the auditory radiation, ending in the cortex of the superior temporal gyrus (cortical section of the auditory analyzer).

The organ of Corti is a peripheral part of the auditory analyzer. Age characteristics

The organ of Corti, located on the basilar membrane, contains receptors that convert mechanical vibrations into electrical potentials that excite the auditory nerve fibers. When exposed to sound, the main membrane begins to vibrate, the hairs of the receptor cells are deformed, which causes the generation of electrical potentials that reach the auditory nerve fibers through synapses. The frequency of these potentials corresponds to the frequency of sounds, and the amplitude depends on the intensity of the sound. As a result of the occurrence of electrical potentials, the auditory nerve fibers are excited, which are characterized by spontaneous activity even in silence (100 impulses/s). During sound, the frequency of impulses in the fibers increases throughout the entire duration of the stimulus. For each nerve fiber there is an optimal sound frequency that gives the highest discharge frequency and minimum response threshold. When the spiral organ is damaged, high tones fall out at the base, and low tones fall out at the apex. The destruction of the middle curl leads to the loss of tones in the middle frequency range. There are two mechanisms for pitch discrimination: spatial and temporal encoding. Spatial coding is based on the unequal location of excited receptor cells on the main membrane. At low and medium tones, time coding is also carried out. A person perceives sounds with a frequency of 16 to 20 O O O Hz. This range corresponds to 10-11 octaves. The limits of hearing depend on age: the older a person is, the more often he does not hear high tones. The difference in frequency of sounds is characterized by the fact that minimal difference by the frequency of two sounds that a person perceives. A person can notice a difference of 1-2 Hz. Absolute hearing sensitivity is the minimum strength of sound heard by a person in half the cases of its sound. In the region from 1000 to 4000 Hz, human hearing has maximum sensitivity. Speech fields also lie in this zone. The upper limit of audibility occurs when an increase in the intensity of a sound of a constant frequency causes an unpleasant feeling of pressure and pain in the ear. The unit of sound loudness is bel. In everyday life, decibels are usually used as a unit of loudness, i.e. 0.1 bel. The maximum volume level when sound causes pain is 130-140 dB above the threshold of audibility. The auditory analyzer has two symmetrical halves (binaural hearing), i.e. Humans are characterized by spatial hearing - the ability to determine the position of a sound source in space. The acuity of such hearing is great. A person can determine the location of a sound source with an accuracy of 1°.

Hearing in ontogenesis

Despite early development auditory analyzer, the hearing organ of a newborn is not yet fully formed. He has relative deafness, which is associated with the structural features of the ear. The newborn reacts to loud sounds by shuddering, stopping crying, and changing breathing. Children's hearing becomes quite clear by the end of the 2nd - beginning of the 3rd month. At the 2nd month of life, the child differentiates qualitatively different sounds, at 3-4 months he distinguishes pitches ranging from 1 to 4 octaves, at 4-5 months sounds become conditioned stimuli, although conditioned food and defensive reflexes to sound stimuli are developed already from 3 months. -5 weeks of age. By 1-2 years, children differentiate sounds, the difference between which is 1 tone, and by 4 years - even 3/4 and 1/2 tones. Hearing acuity is determined by the lowest sound intensity that can cause a sound sensation (hearing threshold). For an adult, the hearing threshold is in the range of 10-12 dB, for children 6-9 years old - 17-24 dB, 10-12 years old - 14-19 dB. The greatest acuity of sound is achieved by middle and high school age.

Question 87. Prevention of Myopiaormyopia, astigmatism, hearing loss. Myopia is a visual impairment in which a person has difficulty seeing objects that are far away and can see close objects well. The disease is very common, affecting one third of the entire world population. Myopia usually appears at the age of 7-15 years, and can worsen or remain at the same level without changes throughout life.

Prevention of myopia: Proper lighting will reduce eye strain, so you should take care of the proper organization of the workplace and a desk lamp. It is not recommended to work under a fluorescent lamp. Compliance with the regime of visual stress, alternating them with physical activity. Proper, balanced nutrition should contain a complex of essential vitamins and minerals: zinc, magnesium, vitamin A, etc. Strengthening the body through hardening, physical activity, massage, contrast shower. Monitor the child's correct posture. These simple precautions can minimize the likelihood of decreased distance vision, that is, the development of myopia. It is important to take all this into account for parents whose child has a hereditary tendency to the disease.

Childhood astigmatism is an optical defect when two optical foci exist simultaneously in the eye, and neither of them is where it should be. This is due to the fact that the cornea refracts rays more strongly along one axis than along the other.

Prevention.

Often children simply do not notice that their vision is decreasing. This means that even if there are no complaints, it is better to show the child to an ophthalmologist once a year. Then the disease will be detected in time, and treatment will begin. Eye exercises for astigmatism are quite useful. Thus, R.S. Agarwal advises making large turns 100 times, moving the gaze along the lines of small print on the vision table, combining them with blinking on each line.

Hearing loss is a hearing loss of varying severity, in which speech perception is difficult, but is possible when certain conditions are created (the speaker or speaker is brought closer to the ear, the use of sound amplifying equipment). When pathology of hearing and speech is combined (deaf-mute), children are not able to perceive and reproduce speech. Prevention of hearing loss and deafness in children is the most important way to solve the problem of hearing loss. A leading role in the prevention of hereditary forms of hearing loss. All pregnant women should undergo examination to detect kidney and liver diseases, diabetes mellitus and other diseases. It is necessary to limit the prescription of ototoxic antibiotics to pregnant women and children, especially younger ones childhood. From the very first days of a child’s life, prevention of acquired forms of hearing loss should be combined with prevention of diseases of the hearing system, especially infectious-viral etiology. If the first signs of hearing impairment are detected, the child should be consulted by an otolaryngologist.