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Abstract: Hearing analyzer. Hearing analyzer, structure, functions Hearing analyzer, structure and functions

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The auditory system is an analyzer of sounds. It distinguishes between sound-conducting and sound-receiving devices (Fig. 1). The sound-conducting apparatus includes the outer ear, middle ear, labyrinthine windows, membranous formations and fluid media of the inner ear; sound-perceiving - hair cells, auditory nerve, neural formations of the brain stem and hearing centers (Fig. 2).


Rice. 1. Schematic structure of the ear (peripheral structure of the auditory analyzer): 1 - outer ear; 2 - middle ear; 3 - inner ear




Rice. 2. Diagram of sound-conducting and sound-receiving devices: 1 - outer ear; 2 - middle ear; 3 - inner ear; 4 - pathways; 5 - cortical center


The sound-conducting apparatus ensures the conduction of acoustic signals to sensitive receptor cells, the sound-perceiving apparatus transforms sound energy into nervous excitement and conducts it to the central sections of the auditory analyzer.

The external ear (amis externa) includes the pinna (auricula) and the external auditory canal (meatus acusticus extemus).

The auricle is an irregularly shaped oval formation near the beginning of the external ear canal. Its basis is elastic cartilage covered with skin. In the lower part of the shell, which is called the lobulus auriculae, there is no cartilage. Instead, there is a layer of fiber under the skin.

In the auricle there are a number of elevations and pits (Fig. 3). Its free, roller-shaped edge is called a helix (helix). The curl starts from the posterior edge of the lobe, stretches along the entire perimeter of the concha and ends above the entrance to the external auditory canal. This part of the auricle is called the helix (cms helicis). In the upper posterior part of the helix, an oval thickening is defined, which is called the duck tubercle (tubercuhtm auriculae).


Rice. 3. Basic anatomical formations auricle: 1 - helix; 2 - leg of the corneal helix; 3 - stem of the helix; 4 - anterior notch; 5 - supratragus tubercle; 6 - tragus; 7 - external auditory canal; 8 - intertragal notch; 9 - antitragus: 10 - lobe (earring); 11 - posterior ear groove; 12 - antihelix; 13 - auricle; 14 - scaphoid fossa; 15 - ear tubercle; 16 - triangular fossa


There is also a second roller - antihelix (anthelix). Between the helix and the antihelix there is a triangular fossa (fossa triangularis). The antihelix ends above the earlobe with an elevation called the antitragus. In front of the antitragus there is a dense cartilaginous formation - the tragus. It partially protects the ear canal from the penetration of foreign bodies into it. The deep fossa, located between the tragus, antihelix and antitragus, makes up the actual concha of the ear (concha auriculae). The muscles of the auricle are rudimentary and have no practical significance.

The auricle passes into the external auditory canal (meatus (icusticus exterrms). The external part of the passage (approximately 1/3 of its length) consists of cartilage, the internal part (2/3 of its length) is bone. The membranous-cartilaginous part of the external auditory canal is mobile, the skin contains hair, sebaceous and sulfur glands. Hair protects the ear from the penetration of insects and foreign bodies; sulfur and ir lubricate and cleanse the ear canal from scales and foreign particles. The skin of the bony part of the external passage is thin, devoid of hair\\ glands, and fits tightly. to the temporal bone.

At the junction of the cartilaginous part and the bone part, the auditory canal narrows somewhat (isthmus). The bony part of the passage has an irregular S-shape, due to which the anterior inferior portions of the tympanic membrane are not sufficiently visible. To expand the space and better see the eardrum, you need to pull the auricle up and back. This structure of the external auditory canal is of practical clinical importance. In particular, the presence sebaceous glands and water only in the cartilaginous part predetermines the occurrence of boils and folliculitis; narrowing of the passage at the border of its membranous-cartilaginous and bone parts is dangerous, since it creates a threat of pushing foreign body into the depths of the ear canal with inept removal.

The outer ear and nearby tissues are supplied with blood from small vessels external carotid artery - a. auhcularis posterior, a. temporalis superfacialis, a. maxillaris interna and others. The innervation of the external ear is carried out by the branches of the V, VII and X cranial nerves. Participation in this process vagus nerve, in particular its ear child (g. auricularis), explains the cause of reflex cough in individual patients with mechanical irritation of the skin of the external auditory canal (wax removal, ear toilet).

The middle ear (auris media) is a system of air cavities, including the tympanic cavity (cavum tympani), cave (antrum), air cells mastoid process(cellulae $astoideas) and auditory tube (tuba auditiva). The outer wall of the tympanic cavity is the eardrum, the inner wall is lateral wall inner ear, upper - the roof of the tympanic cavity (tegmen tympani), separating the tympanic cavity from the middle cranial fossa, lower - bone formation, separating the bulb jugular vein(bulbus venae jugularis).

On the front wall there is a tympanic opening of the auditory tube and a canal for the muscle that strains the tympanic membrane (tensor tympani), on the back there is an entrance to the cave (aditus ad antrum), which connects the tympanic cavity through the epitympanic space (attic) with the mastoid cave ( antrum mastoideum). The auditory tube connects the tympanic cavity to the nasal part of the throat. Behind and below the opening of the auditory tube there is a bone canal in which the internal carotid artery passes, with its branches providing blood supply to the inner ear. Anatomical structure

DI. Zabolotny, Yu.V. Mitin, S.B. Bezshapochny, Yu.V. Deeva

The auditory analyzer is the most important part of the human sensory system. The structure of the auditory analyzer allows people to communicate with each other through sound transmission, perceive, interpret and respond to sound information: when a car approaches, thanks to the sounds perceived through hearing, a person moves out of the road in time, which allows him to avoid a dangerous situation.

Sound waves are vibrations in solid, liquid or gaseous environment, which can be heard with the help of the hearing organ. Sound is defined in the audible range of the spectrum, just as light is defined in the visible part of the electromagnetic wave spectrum.

Vibrations of sound waves are the propagation of motion at the molecular level, which is characterized by the movement of molecules around a state of equilibrium. In the process of this movement, which is created mechanically, the molecules are subjected to acoustic pressure, which causes them to collide with each other and transmit these vibrations further. When the transfer of energy stops, the displaced molecules return to their original position.

The similarity between the visual and auditory analyzers is that they are both capable of perceiving specific qualities, selecting them from the general sound stream. For example, the location of the sound source, its volume, timbre, etc. But the physiology of the auditory analyzer functions in such a way that the human auditory system does not mix different frequencies, as vision does when different wavelengths of light are mixed with each other - and the ocular analyzer represents this as a continuous color.

Instead sound analyzer separates complex sounds into their component tones and frequencies so that a person can distinguish the voices of specific people in a general hum or individual instruments in the sounds of an orchestra. Features of hearing abnormalities make it possible to identify various audiometric methods for studying the auditory analyzer.

Outer and middle ear

The way the auditory analyzer is structured affects the functioning of its structures, parts of the ear, subcortical relay and cortical centers. The anatomy of the auditory analyzer includes the structure of the ear, stem and cortical parts of the brain. The sections of the auditory analyzer are:

  • peripheral part of the auditory analyzer;
  • cortical end of the auditory analyzer.

According to the diagram, the structure of the ear consists of 3 parts. The outer and middle ear transmit sounds to the inner ear, where they are converted into electrical impulses for processing by the nervous system. Thus, the functions of the auditory analyzer are divided into sound-conducting and sound-perceiving.

The outer, middle and inner ear are the peripheral parts of the auditory analyzer. The outer part of the ear consists of the pinna and the auditory canal. This passage closes with inside eardrum. The auditory analyzer, the structure and functions of which include the peripheral section of the auditory analyzer, acts as an acoustic antenna.

Sound waves are collected into pieces outer ear, which is called the auricle and reaches the eardrum through the ear canal, causing it to vibrate. Thus, the outer ear acts as a resonator, which amplifies sound vibrations.

The eardrum is the end of the outer ear. Then the middle begins, which communicates with the nasopharynx through the Eustachian tubes. The age-related features of the auditory analyzer are that in newborns the middle ear cavity is filled with amniotic fluid, which by the third month is replaced by air that enters here through the Eustachian tubes. In the middle ear cavity, the eardrum is connected by a chain of three auditory ossicles with another membrane called the oval window. It closes the cavity of the inner ear.

The first bone, the malleus, vibrates under the action of the eardrum, transmits these vibrations to the incus, which causes the stirrup to vibrate, which presses on the oval window in the cochlea. The base of the stapes has mechanical pressure, amplified tens of times, onto the oval window, as a result of which the perilymph in the cochlea begins to fluctuate. In addition to the oval window, there is a round window, which also separates the cavity of the middle ear and the inner ear.

The ratio of the eardrum to the surface of the oval window is 20:1, which makes it possible to amplify sound vibrations twenty times. This is necessary so that the vibration of fluid in the inner ear requires much more energy than the average vibration of air.

Inner ear

The inner ear contains two different organs - the auditory and vestibular analyzers. Due to this, the schematic structure of the inner ear provides for the presence of:

  • vestibule;
  • semicircular canals (responsible for coordination);
  • cochlea (responsible for hearing).

Both analyzers have similar morphological and physiological properties. Among them are hair cells and the mechanism for transmitting information to the brain.

The discrimination of sound frequencies begins in the cochlea of ​​the inner ear. It is designed in such a way that its different parts respond to different pitches of sound vibrations. High notes vibrate some parts of the basilar membrane of the cochlea, low notes vibrate others.

The basilar membrane contains hair cells, at the top of which there are entire bundles of stereocilia, which are deflected by the membrane located on top. Hair cells convert mechanical vibrations into electrical signals that auditory nerve go to the brain stem. Thus, the conductive section of the auditory analyzer is represented by fibers of the auditory nerve. Because each hair cell has its own location in the basilar membrane, each cell transmits a different pitch of sound to the brain.

Structure of the cochlea

The cochlea is the “hearing” part of the inner ear, which is located in the temporal part of the skull. It gets its name from its spiral shape, reminiscent of a snail shell.

The cochlea consists of three channels. Two of them, the scala tympani and the scala vestibule, are filled with a fluid called perilymph. The interaction between them occurs through a small hole called helicotrema. In addition, between the scala tympani and scala vestibuli, neurons of the spiral ganglion and fibers of the auditory nerve are located on the inner side.

The third canal, scala media, is located between the scala tympani and scala vestibule. It is filled with endolymph. Between the scala media and the scala tympani on the basilar membrane there is a structure called the organ of Corti.

The cochlear ducts are composed of two types of fluid, perilymph and endolymph. Perilymph has the same ionic composition as extracellular fluid in any other part of the body. It fills the scala tympani and scala vestibule. The endolymph that fills the scala media has a unique composition intended only for this part of the body. First of all, it is very rich in potassium, which is produced in the stria vascularis, and very poor in sodium. It also contains virtually no calcium.

Endolymph has a positive electrical potential (+80 mV) relative to perilymph, which is rich in sodium. The organ of Corti in the upper part, where the stereocilia are located, is moistened by endolymph, and at the base of the cells by perilymph.

Using this method, the cochlea is able to carry out a very complex analysis of sounds, both in terms of their frequency and volume. When the pressure of sounds is transmitted to the fluid of the inner ear by the stapes, the pressure of the waves deforms the basilar membrane in the area of ​​the cochlea that is responsible for these vibrations. Thus, higher notes cause the base of the cochlea to vibrate, and lower notes cause its top to vibrate.

It has been proven that the human cochlea is capable of perceiving sounds of different tones. Their frequency can vary from 20 Hz to 20,000 Hz (approximately the 10th octave), in steps of 1/230 octave (from 3 Hz to 1 thousand Hz). At a frequency of 1 thousand Hz, the cochlea is able to encode the pressure of sound waves in the range between 0 dB and 120 dB.

Auditory cortex

In addition to the ear and auditory nerve, the auditory analyzer includes the brain. Sound information is analyzed in different centers in the brain as the signal is sent to the superior temporal gyrus of the brain. This is the auditory cortex, which performs the sound-processing function of the human auditory analyzer. Here is huge amount neurons, each of which performs its own task. For example, there are neurons that:

  • react to pure tones (flute sounds);
  • recognize complex tones (violin sounds);
  • responsible for long sounds;
  • react to short sounds;
  • respond to changes in sound volume.

There are also neurons that can be responsible for complex sounds, for example, identifying a musical instrument or a word of speech. Connections between the auditory and speech motor analyzers allow a person to learn foreign languages.

Sound information is processed in various areas sound cortex in both hemispheres of the brain. For most people, the left side of the brain is responsible for the perception and production of speech. Therefore, damage to the left auditory cortex during a stroke can lead to the fact that although a person will hear, he will not be able to understand speech.

Primary path

Sound information is collected in the brain by two pathways of the auditory analyzer:

  • The primary auditory pathway, which carries messages exclusively from the cochlea.
  • The non-primary auditory pathway, also called the reticular sensory pathway. It conveys messages from all senses.

The primary path is short and very fast, since the speed of impulse transmission is provided by fibers with a thick layer of myelin. This pathway ends in the auditory cortex of the brain, which is located in the lateral sulcus of the temporal part of the brain.

The primary pathways of the auditory analyzer conduct nerve impulses from the sound-sensitive cells of the cochlea. At the same time, at each end point of the transmission link, decoding and integration of nerve impulses occurs nuclear cells snails

The first switching nucleus of the primary auditory pathway is located in the cochlear nuclei, which is located in the brain stem. Nerve impulses travel along spiral gangliary axons of type 1. At this level of switching, nerve sound signals are deciphered, which characterize the duration, intensity and frequency of the sound.

The second and third switching nuclei of the primary auditory pathway play a significant role in determining the location of the sound source. The second switching nucleus in the brainstem is called the superior olivary complex. At this level, most auditory nerve synapses have crossed the central line. The third switching nucleus is located at the level of the midbrain.

And finally, the fourth switching nucleus is located in the thalamus. Here, significant integration of sound information occurs, and preparation for motor reaction(for example, making sounds in response).

The last neuron of the primary pathway connects the thalamus and the auditory cortex of the brain. Here the message, most of which was deciphered on the way here, is recognized, stored and integrated for further random use.

Non-primary paths

From the cochlear nuclei, small nerve fibers pass into the reticular formation of the brain, where sound messages are combined with nerve messages that come here from other senses. The next switching point is the nonspecific nuclei of the thalamus, after which this auditory pathway ends in the polysensory associative cortex.

The main function of these auditory pathways is the production of nerve messages that are subject to priority processing. To do this, they connect to the centers of the brain responsible for the feeling of wakefulness and motivation, as well as to the autonomic nervous and endocrine systems. For example, if a person is doing two things at once, reading a book and listening to music, this system will direct attention to more important work.

The first transfer point of the non-primary auditory pathway, as well as the primary one, is located in the cochlear nuclei of the brain stem. From here, small fibers join the reticular tract of the brainstem. Here, as well as in the midbrain, there are several synapses where auditory information is processed and integrated with information from other senses.

In this case, information is filtered by primary priority. In other words, the role of the reticular formation of the brain is to connect nerve messages from other centers (wakefulness, motivation) to the processed sound information, so that there is a selection of nerve messages that will be processed in the brain first. After the reticular formation, non-primary pathways lead to nonspecific centers in the thalamus, and then to the polysensory cortex.

It must be understood that conscious perception requires the integration of both types of auditory neural pathways, primary and non-primary. For example, during sleep, the primary auditory pathway functions normally, but conscious perception is impossible because the connection between the reticular pathway and the centers of wakefulness and motivation is not activated.

Conversely, as a result of trauma to the cortex, conscious perception of sounds may be impaired, while continued integration of non-primary auditory pathways may result in autonomic responses to sound. nervous system. In addition, if the brainstem and midbrain are intact, the startle and surprise response may remain, even in the absence of understanding the meaning of the sounds.

1. What are the features of the economic-geographical approach to assessing the ecological state of a territory?

2. What factors determine the ecological state of the territory?

3. What types of zoning, taking into account the environmental factor, are distinguished in modern geographical literature?

4. What are the criteria and what are the features of ecological, ecological-economic and natural-economic zoning?

5. How can anthropogenic impact be classified?

6. What can be classified as the primary and secondary consequences of anthropogenic impact?

7. How have the main parameters of anthropogenic impact changed in Russia in transition period?

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Chapter 3. STRUCTURE AND FUNCTIONS OF THE HEARING ANALYZER.

3.1 Structure of the hearing organ. The peripheral section of the auditory analyzer is represented by the ear, with the help of which a person perceives the influence external environment, expressed in the form of sound vibrations that exert physical pressure on the eardrum. A person receives significantly less information through the organ of hearing than through the organ of vision (approximately 10%). But the rumor has great value For general development and the formation of personality and, in particular, for the development of speech in a child, which has a decisive influence on his mental development.

The organ of hearing and balance contains several types of sensory cells: receptors that perceive sound vibrations; receptors that determine the position of the body in space; receptors that perceive changes in direction and speed of movement. There are three parts of the organ: the outer, middle and inner ear (Fig. 7).

The outer ear receives sounds and directs them to eardrum. It includes conducting sections - the auricle and the external auditory canal.

Rice. 7. The structure of the hearing organ.

The auricle consists of elastic cartilage covered with a thin layer of skin. The external auditory canal is a curved canal 2.5–3 cm long. The canal has two sections: the cartilaginous external auditory canal and the internal bony auditory canal, located in the temporal bone. The external auditory canal is lined with skin with fine hairs and special sweat glands which secrete earwax.

Its end is closed from the inside by a thin translucent plate - the eardrum, separating the outer ear from the middle ear. The latter includes several formations enclosed in the tympanic cavity: the eardrum, the auditory ossicles, and the auditory (Eustachian) tube. On the wall facing the inner ear there are two openings - the oval window (window of the vestibule) and the round window (window of the cochlea). On the wall of the tympanic cavity, facing the external auditory canal, there is an eardrum that perceives sound vibrations in the air and transmits them to the sound conducting system of the middle ear - the complex of auditory ossicles (it can be compared to a kind of microphone). The barely noticeable vibrations of the eardrum are amplified and transformed here, transmitted to the inner ear. The complex consists of three bones: the malleus, the anvil and the stapes. The malleus (8–9 mm long) is tightly fused with the inner surface of the eardrum with its handle, and the head is articulated with the anvil, which, due to the presence of two legs, resembles a molar with two roots. One leg (long) serves as a lever for the stirrup. The stirrup has a size of 5 mm, with its wide base inserted into the oval window of the vestibule, tightly adjacent to its membrane. The movements of the auditory ossicles are provided by the tensor tympani muscle and the stapedius muscle.

The auditory tube (3.5 - 4 cm long) connects the tympanic cavity with the upper part of the pharynx. Through it, air enters the middle ear cavity from the nasopharynx, thereby equalizing the pressure on the eardrum from the external auditory canal and the tympanic cavity. When the passage of air through the auditory tube is difficult (inflammatory process), pressure from the external auditory canal prevails, and the eardrum is pressed into the cavity of the middle ear. This leads to a significant loss of the ability of the eardrum to vibrate in accordance with the frequency of sound waves.

The inner ear is a very complex organ; it looks like a labyrinth or a snail with 2.5 circles in its “house”. It is located in the pyramid of the temporal bone. Inside the bony labyrinth there is a closed connecting membranous labyrinth, repeating the shape of the external one. The space between the walls of the bony and membranous labyrinths is filled with fluid - perilymph, and the cavity of the membranous labyrinth is filled with endolymph.

The vestibule is a small oval cavity in the middle part of the labyrinth. On the medial wall of the vestibule, a ridge separates two fossae. Posterior fossa- elliptical recess - lies closer to the semicircular canals, which open into the vestibule with five openings, and the anterior - spherical recess - is connected to the cochlea.

In the membranous labyrinth, which is located inside the bone labyrinth and basically follows its outline, elliptical and spherical sacs are distinguished.

The walls of the sacs are covered flat epithelium, with the exception of a small area - spots. The spot is lined with columnar epithelium containing supporting and hair sensory cells, which have thin processes on their surface facing the cavity of the sac. The nerve fibers of the auditory nerve (its vestibular part) begin from the hair cells. The surface of the epithelium is covered with a special fine-fibrous and gelatinous membrane, called otolithic, since it contains otolith crystals consisting of calcium carbonate.

Three mutually perpendicular semicircular canals adjoin the vestibule posteriorly - one in the horizontal and two in the vertical planes. All of them are narrow tubes filled with liquid - endolymph. Each channel ends with an extension - an ampoule; in its auditory crest the cells of the sensitive epithelium are concentrated, from which the branches of the vestibular nerve begin.

In front of the vestibule is the cochlea. The cochlear canal bends in a spiral and forms 2.5 turns around the rod. The cochlear shaft consists of spongy bone tissue, between the beams of which nerve cells are located, forming a spiral ganglion. A thin bone sheet extends from the rod in the form of a spiral, consisting of two plates, between which the myelinated dendrites of the neurons of the spiral ganglion pass. The upper plate of the bony leaf passes into the spiral lip, or limbus, the lower one into the spiral main, or basilar, membrane, which extends to the outer wall of the cochlear canal. The dense and elastic spiral membrane is a connective tissue plate that consists of the main substance and collagen fibers - strings stretched between the spiral bone plate and the outer wall of the cochlear canal. At the base of the cochlea the fibers are shorter. Their length is 104 microns. Towards the apex, the length of the fibers increases to 504 µm. Their total number is about 24 thousand.

From the bone spiral plate to the outer wall of the bone canal, at an angle to the spiral membrane, another membrane extends, less dense - vestibular, or Reisner's.

The cavity of the cochlear canal is divided by membranes into three sections: the upper canal of the cochlea, or vestibular scala, starts from the window of the vestibule; the middle canal of the cochlea - between the vestibular and spiral membranes and the lower canal, or scala tympani, starting from the window of the cochlea. At the apex of the cochlea, the scala vestibular and scala tympani communicate through a small opening, the helicotrema. The upper and lower canals are filled with perilymph. The middle canal is the cochlear duct, which is also a spirally convoluted canal with 2.5 turns. On the outer wall of the cochlear duct there is a vascular strip, the epithelial cells of which have secretory function, producing endolymph. The vestibular and tympanic scalae are filled with perilymph, and the middle canal is filled with endolymph. Inside the cochlear duct, on the spiral membrane, is located complex device(in the form of a protrusion of the neuroepithelium), which is the actual perceptive apparatus of auditory perception - the spiral (Corti) organ (Fig. 8).

The organ of Corti is formed by sensory hair cells. There are inner and outer hair cells. Inner hair cells bear on their surface from 30 to 60 short hairs arranged in 3 to 5 rows. The number of inner hair cells in humans is about 3500. The outer hair cells are arranged in three rows, each of them has about 100 hairs. The total number of outer hair cells in humans is 12–20 thousand. Outer hair cells are more sensitive to sound stimuli than inner ones.

Above the hair cells is the tectorial membrane. It has a ribbon-like shape and a jelly-like consistency. Its width and thickness increase from the base of the cochlea to the apex.

Information from hair cells is transmitted along the dendrites of the cells forming a spiral knot. The second process of these cells - the axon - as part of the vestibular-cochlear nerve is directed to the brain stem and to the diencephalon, where a switch occurs to the next neurons, the processes of which go to the temporal part of the cerebral cortex.

Rice. 8. Diagram of the organ of Corti:

1 - cover plate; 2, 3 - outer (3-4 rows) and inner (1st row) hair cells; 4 - supporting cells; 5 - fibers of the cochlear nerve (in cross section); 6 - external and internal pillars; 7 - cochlear nerve; 8 - main plate

spiral organ is a device that receives sound stimulation. The vestibule and semicircular canals provide balance. A person can perceive up to 300 thousand different shades of sounds and noise in the range from 16 to 20 thousand Hz. The outer and middle ear are capable of amplifying sound almost 200 times, but only weak sounds are amplified, strong sounds are attenuated.

3.2 Mechanism of sound transmission and perception. Sound vibrations are picked up by the auricle and transmitted through the external auditory canal to the eardrum, which begins to vibrate in accordance with the frequency of the sound waves. Vibrations of the eardrum are transmitted to the chain of ossicles of the middle ear and, with their participation, to the membrane oval window. Vibrations of the membrane of the vestibule window are transmitted to the perilymph and endolymph, which causes vibrations of the main membrane along with the organ of Corti located on it. In this case, the hair cells touch the tectorial membrane with their hairs, and as a result mechanical irritation excitation arises in them, which is transmitted further to the fibers of the vestibulocochlear nerve.

The human auditory analyzer perceives sound waves with a frequency of oscillations from 20 to 20 thousand per second. The pitch of the tone is determined by the frequency of vibrations: the higher it is, the higher the pitch of the perceived sound. Analysis of sounds by frequency is carried out by the peripheral section of the auditory analyzer. Under the influence of sound vibrations, the membrane of the vestibule window bends, thereby displacing some volume of perilymph. At a low oscillation frequency, perilymph particles move along the vestibular scala along the spiral membrane towards the helicotrema and through it along the scala tympani to the round window membrane, which bends by the same amount as the oval window membrane. If a high frequency of oscillations occurs, a rapid displacement of the membrane of the oval window occurs and an increase in pressure in the vestibular scala. This causes the spiral membrane to bend towards the scala tympani and the portion of the membrane near the window of the vestibule reacts. When the pressure in the scala tympani increases, the membrane of the round window bends; the main membrane, due to its elasticity, returns to its original position. At this time, the perilymph particles displace the next, more inertial section of the membrane, and the wave runs across the entire membrane. Oscillations of the vestibule window cause a traveling wave, the amplitude of which increases, and its maximum corresponds to a specific part of the membrane. Upon reaching the maximum amplitude, the wave fades out. The higher the height of sound vibrations, the closer to the vestibule window the maximum amplitude of vibrations of the spiral membrane is located. The lower the frequency, the closer to the helicotreme its greatest fluctuations are noted.

It has been established that under the influence of sound waves with an oscillation frequency of up to 1000 per second, the entire perilymph column of the scala vestibularis and the entire spiral membrane vibrate. In this case, their vibrations occur in exact accordance with the frequency of sound waves. Accordingly, action potentials arise in the auditory nerve with the same frequency. When the frequency of sound vibrations exceeds 1000, not the entire main membrane vibrates, but some part of it, starting from the window of the vestibule. The higher the frequency of oscillations, the shorter the length of the membrane section, starting from the window of the vestibule, comes into vibration and the fewer the number of hair cells comes into a state of excitation. In this case, action potentials are recorded in the auditory nerve, the frequency of which is lower than the frequency of sound waves acting on the ear, and with high-frequency sound vibrations, impulses arise in fewer fibers than with low-frequency vibrations, which is associated with excitation of only a part of the hair cells.

This means that during the action of sound vibrations, spatial coding of sound occurs. The sensation of a particular pitch of sound depends on the length of the vibrating section of the main membrane, and, consequently, on the number of hair cells located on it and on their location. The fewer oscillating cells and the closer they are located to the window of the vestibule, the higher the sound is perceived.

Vibrating hair cells cause excitation in strictly defined fibers of the auditory nerve, and therefore in certain nerve cells brain.

The strength of sound is determined by the amplitude of the sound wave. The sensation of sound intensity is associated with a different ratio of the number of excited inner and outer hair cells. Since internal cells are less excitable than external cells, excitation of a large number of them occurs under the influence of strong sounds.

3.3 Age-related characteristics of the auditory analyzer. The formation of the cochlea occurs at the 12th week of intrauterine development, and at the 20th week myelination of the fibers of the cochlear nerve begins in the lower (main) curl of the cochlea. Myelination in the middle and superior curls of the cochlea begins much later.

Differentiation of the sections of the auditory analyzer, which are located in the brain, is manifested in the formation of cell layers, in an increase in the space between cells, in cell growth and changes in their structure: in an increase in the number of processes, spines and synapses.

Subcortical structures related to the auditory analyzer mature earlier than its cortical section. Their qualitative development ends in the 3rd month after birth. The structure of the cortical fields of the auditory analyzer differs from that in adults up to 2–7 years of age.

The auditory analyzer begins to function immediately after birth. Already in newborns, it is possible to carry out a basic analysis of sounds. The first reactions to sound are orientation reflexes carried out at the level of subcortical formations. They are observed even in premature babies and are manifested in closing the eyes, opening the mouth, shuddering, decreasing the frequency of breathing, pulse, and various facial movements. Sounds that are the same in intensity, but different in timbre and pitch, cause different reactions, which indicates the ability of a newborn child to distinguish them.

Conditioned food and defensive reflexes to sound stimulation are developed from 3 to 5 weeks of a child’s life. Strengthening of these reflexes is possible only from 2 months of life. Differentiation of different sounds is possible from 2 to 3 months. At 6–7 months, children differentiate tones that differ from the original by 1–2 and even 3–4.5 musical tones.

Functional development development of the auditory analyzer lasts up to 6–7 years, which is manifested in the formation of subtle differentiations to speech stimuli. Children of different ages have different hearing thresholds. Hearing acuity and, consequently, the smallest hearing threshold decrease until 14–19 years of age, when the lowest threshold value is noted, and then increase again. Sensitivity of the auditory analyzer to different frequencies varies at different ages. Before 40 years of age, the lowest threshold of hearing drops to a frequency of 3000 Hz, at 40-49 years of age - 2000 Hz, after 50 years - 1000 Hz, and from this age the upper limit of perceived sound vibrations decreases.

The structure of the auditory analyzer is the topic of our article. How are its structure and functions related? What is the importance of hearing for a person? Let's figure it out together.

What are sensory systems

Every second, our body perceives information from the environment and reacts to it accordingly. This is possible thanks to sensor or analyzing systems. The structure of the auditory analyzer is similar to other similar structures.

In total, there are five sensory systems in the human body. In addition to auditory, these include visual, olfactory, tactile, and gustatory. Scientists say that humans also have a sixth sense. We are talking about intuition - the ability to foresee events. But the structure that is responsible for the formation of this feeling is still unknown.

Operating principle of analyzers

If we briefly describe the structure of the auditory analyzer, we can name its three sections. They are called peripheral, conduction and central. All sensory systems have such a structure.

The peripheral section is represented by receptors. These are sensitive formations that perceive various types of irritations and convert them into impulses. Nerve fibers, which represent the conduction section, transmit information to the brain. Here it is analyzed and a response to irritation is formed.

Structure and functions of the auditory analyzer: briefly

How do we perceive sound vibrations? The structure of the auditory analyzer is similar to all others. Its peripheral section is represented by the ear. The conduction nerve is the auditory nerve. Along it, nerve impulses move to the central part. This is the auditory area of ​​the cerebral cortex.

Adaptability

A common property for all sensory systems is their ability to adapt the level of their sensitivity to the intensity of the stimulus. This property is also called adaptation. And the structure of the human auditory analyzer is no exception.

What is the essence of the adaptation process? The fact is that the sensitivity of auditory receptors can be adjusted depending on the degree of exposure to the stimulus. If the signal is strong, the level of perception decreases, and vice versa. For example, remember how we gradually begin to distinguish quiet sounds after a certain time.

For the human body, adaptation has a protective significance. It also improves the functionality of the analyzers through long repetitions. This is how professional musicians train their ears. People who work in conditions of intense noise for a long time or live next to a railway stop noticing it after a certain period. This is also a manifestation of adaptation.

Like all sensory systems, the auditory system is compensated by the functioning of the others. A striking example of this is the greatest composer Ludwig Beethoven. He was a recognized master already in at a young age, and by the age of thirty his deafness began to progress rapidly. But even when Beethoven completely lost his hearing, he continued to compose musical masterpieces. He placed a small wooden stick in his mouth and pressed it against the musical instrument. In this way, the tactile sensory system compensated for the auditory analyzer. And the lack of vision is partially replaced by developed hearing and smell.

The meaning of hearing

Is it possible to live deaf? Naturally, there are a huge number of people with hearing impairments. Despite the fact that a person perceives most information through vision, the perception of sounds is also of great importance.

The basic principles of the structure of the auditory analyzer make its operation continuous. We hear even during sleep. Hearing allows you to perceive information at a distance, transfer experience across generations, and is a means of communication.

What is sound pressure

Are we able to perceive all sounds? Far from it. In the process of evolution, sensory systems have adapted to analyze information only in a certain range. This protects the brain from overload.

Sounds are formed from air vibrations. The structure of the auditory analyzer ensures their transformation into nerve impulses, which are analyzed in the brain. The amplitude of such oscillations is called sound pressure. Its unit of measurement is decibel. During a normal conversation, this value is 60 dB.

The frequency of sound vibrations is measured in hertz. We perceive a very narrow range - from 16 to 20 kHz. We are unable to hear other vibrations. If the vibration frequency is below 16 Hz, it is called infrasound. In nature, it is used for communication by whales and elephants.

Ultrasound occurs at vibration frequencies greater than 20 kHz. Bats use it for orientation at night. They make sounds that are reflected from objects. This method is called echolocation.

Hearing organ

The auditory analyzer, the structure and functions of which we discuss in our article, consists of three sections. The peripheral is represented by the ear. Or more correctly, the organ of hearing. Next comes the wiring department. This is the auditory nerve. It transmits information to central department, represented by the auditory cortex of the telencephalon.

Outer ear

What are the features of the anatomical structure of the peripheral part of the auditory analyzer? First of all, it also consists of three parts. These are the outer, middle and inner ear.

The elements of the first part are the auricle and the external auditory canal. They capture and direct sound vibrations to internal departments. The auricle is formed by elastic cartilage tissue, which forms characteristic curls.

The external auditory canal is about 2.5 cm long, ending at the eardrum. His skin is rich in modified sweat glands. They secrete a special substance - earwax. Together with hairs, it traps dust and microorganisms.

Auditory ossicles

The structure of the hearing organ and auditory analyzer continues with the middle ear. Sound vibrations are transmitted to the eardrum, causing it to vibrate. The higher the sound, the more intense the vibrations.

The location of the middle ear is the skull. Its boundaries are two membranes - the tympanic membrane and the oval window. Here the vibrations are transmitted to the auditory ossicles. They have characteristic shape, which determines their names: hammer, stirrup and incus. The auditory ossicles are anatomically connected to each other. The narrow part of the hammer is attached to the anvil. The latter is movably connected to the stirrup. Vibrations from the eardrum travel through the auditory ossicles to the membrane of the oval window.

In this section, the middle ear is anatomically connected to the nasopharynx using the eustachian, or auditory tube. This structure allows air from the environment to penetrate here. Therefore, the pressure on the eardrum is equal on both sides.

Inner ear

Much has already been said about the structure and functions of the auditory analyzer, but not a word about the receptors themselves. This is not a mistake. They are contained by the inner ear. Its location is the temporal bone. It is a complex system of convoluted tubules and cavities. They are filled with a special liquid.

From the oval window, the structure of the auditory analyzer continues with a canal consisting of 2.5 turns. This is the cochlea, which contains the auditory receptors, or hair cells. In the cochlea, there are main and integumentary membranes. The first is formed from transverse fibers having different lengths. There are a lot of them - up to 24 thousand. The integumentary membrane overhangs the hair cells. As a result, a sound-receiving apparatus is formed, which is called the organ of Corti. It consists of membranes and auditory receptors.

Mechanism of action

When the membrane of the oval window begins to vibrate, this irritation is transmitted to the cochlear fluid. As a result, the phenomenon of resonance occurs. Vibrations of fibers of different lengths and auditory receptors begin.

This process has its own laws. A strong sound causes a large sweep oscillatory movements fibers At high pitches, short fibers begin to resonate.

Next, the mechanical energy of the oscillatory movements is converted into electrical energy. This is how nerve impulses arise. Their further movement occurs with the help of neurons and their processes. They enter the auditory cortex of the telencephalon, which is located in the temporal lobe.

Sound analysis - also important function auditory analyzer. The brain determines the strength of sound, its character, height, direction in space. The intonation of words is also perceived. As a result, a sound image is formed.

Even with our eyes closed, we can determine from which direction the signal is heard. What makes this possible? If sound enters both ears, we perceive the sound in the middle. Or rather, front and back. If sound enters one ear earlier than the other, then the sound is perceived from the right or left.

Have you ever noticed that people perceive the same sound differently? For one, the TV is too quiet, while the other cannot hear anything. It turns out that each person has his own threshold of auditory sensitivity. What does this indicator depend on? It is determined not only by the structure, functions and age characteristics of the auditory analyzer. People aged 15 to 20 years have the most acute perception of sounds. Further, hearing acuity gradually decreases.

There is also such a thing as the threshold of hearing. This is the smallest sound strength at which it begins to be perceived. This indicator is also determined by individual characteristics.

The process of forming an auditory analyzer

When does a person begin to perceive sounds? Immediately after birth. The response to sounds during this period is the manifestation of conditioned reflexes. This continues for about two months. Now the body already reacts conditionally. For example, a mother's voice becomes a sign of feeding.

By the third month, the baby can already distinguish the tone, timbre, pitch and direction of sounds. By the age of one year, as a rule, the child already understands the semantic meaning of words.

Hearing hygiene

The structure of the auditory analyzer, although completely natural, requires constant attention. The most basic rules of hygiene will allow you to maintain the ability to perceive sounds for a long time.

The simplest reason for sound deterioration is the accumulation of wax in the external auditory canal. If this substance is not removed, so-called plugs may form. To prevent this, sulfur must be removed periodically.

We also need to take the consequences of viral diseases seriously. The most basic rhinitis, sore throat or flu can lead to inflammation in the middle ear. This disease is called otitis media. Dangerous microorganisms enter the middle ear from the nasopharynx through the auditory tube.

Hearing loss can also be caused by purely mechanical reasons. One of them is damage to the eardrum. It can also be caused by the action sharp object, and excessively loud sound. For example, an explosion. If you expect this to happen, you need to open your mouth. This action makes the pressure on both sides of the eardrum equal.

But let's get back to everyday life. We do not think that the systematic use of headphones, constant household and traffic noise gradually reduce the elasticity of the ear drum. As a result, hearing acuity decreases significantly. But this process is irreversible. Just imagine that a pneumatic drill operates with a sound intensity of up to 100 decibels, and a disco - 110!

So, the human auditory sensory system consists of three sections, such as:

  • Peripheral. Represented by the organ of hearing: the outer, middle and inner ear. The curls of the auricle direct air vibrations into the external auditory canal, from there to specialized bones (the malleus, stem and incus), the membrane of the oval window and the cochlea. The last structure contains hair cells. These are auditory receptors that convert mechanical vibrations into nerve impulses.
  • Conductive. This is the auditory nerve through which impulses are transmitted.
  • Central. Found in the cortex big brain. Here the information is analyzed, resulting in the formation of sound sensations.

Sound waves are vibrations transmitted at a certain frequency in all three media: liquid, solid and gaseous. For human perception and analysis, there is an organ of hearing - the ear, which consists of outer, middle and inner parts, capable of receiving information and transmitting it to the brain for processing. This principle of operation in the human body is similar to that characteristic of the eyes. The structure and functions of the visual and auditory analyzers are similar to each other, the difference is that the ear does not mix sound frequencies, perceives them separately, rather, even separating different voices and sounds. In turn, the eyes connect light waves, while receiving different colors and shades.

Hearing analyzer, structure and functions

Photos of the main departments human ear you can see in this article. The ear is the main organ of hearing in humans; it receives sound and transmits it further to the brain. The structure and functions of the auditory analyzer are much broader than the capabilities of the ear alone; it is a coordinated work of transmitting impulses from the eardrum to the stem and cortical parts of the brain responsible for processing the received data.

The organ responsible for the mechanical perception of sounds consists of three main sections. The structure and functions of the sections of the auditory analyzer are different from each other, but they perform one common job - the perception of sounds and their transmission to the brain for further analysis.

Outer ear, its features and anatomy

The first thing that sound waves encounter on the way to the perception of their semantic load is its anatomy is quite simple: this is the auricle and the external auditory canal, which is the connecting link between it and the middle ear. The auricle itself consists of a cartilaginous plate 1 mm thick, covered with perichondrium and skin; it is devoid of muscle tissue and cannot move.

The lower part of the shell is the earlobe, it is fatty tissue, covered with skin and penetrated by many nerve endings. The concha smoothly and funnel-shaped passes into the auditory canal, bounded by the tragus in front and the antitragus in the back. In an adult, the passage is 2.5 cm in length and 0.7-0.9 cm in diameter; it consists of internal and membranous cartilaginous sections. It is limited by the eardrum, behind which the middle ear begins.

The membrane is an oval-shaped fibrous plate, on the surface of which elements such as the malleus, posterior and anterior folds, umbilicus and short process can be distinguished. The structure and functions of the auditory analyzer, represented by such parts as the outer ear and the eardrum, are responsible for capturing sounds, their primary processing and transmission further to the middle part.

Middle ear, its features and anatomy

The structure and functions of the sections of the auditory analyzer are radically different from each other, and if everyone is familiar with the anatomy of the outer part firsthand, then more attention should be paid to studying information about the middle and inner ear. The middle ear consists of four air cavities connected to each other and an incus.

The main part that performs the main functions of the ear is the auditory tube, combined with the nasopharynx, through which the entire system is ventilated. The cavity itself consists of three chambers, six walls and which, in turn, is represented by the hammer, anvil and stirrup. The structure and functions of the auditory analyzer in the middle ear transform the sound waves received from the outer part into mechanical vibrations, after which they transmit them to the fluid, which fills the cavity of the inner part of the ear.

Inner ear, its features and anatomy

The inner ear is the most complex system of all three parts of the hearing system. It looks like a labyrinth, which is located in the thickness of the temporal bone, and is a bone capsule and a membranous formation included in it, which completely repeats the structure of the bone labyrinth. Conventionally, the entire ear is divided into three main parts:

  • the middle labyrinth is the vestibule;
  • anterior labyrinth - cochlea;
  • posterior labyrinth - three semicircular canals.

The labyrinth completely repeats the structure of the bone part, and the cavity between these two systems is filled with perilymph, reminiscent in its composition of plasma and cerebrospinal fluid. In turn, the cavities in the cell itself are filled with endolymph, which is similar in composition to intracellular fluid.

Hearing analyzer, inner ear receptor function

Functionally, the work of the inner ear is divided into two main functions: transmitting sound frequencies to the brain and coordinating human movements. The main role in transmitting sound to parts of the brain is played by the cochlea, different parts of which perceive vibrations with different frequencies. All these vibrations are absorbed by the basilar membrane, covered with hair cells with bundles of stereolicia at the top. It is these cells that convert vibrations into electrical impulses that travel to the brain along the auditory nerve. Each hair of the membrane has a different size and receives sound only at a strictly defined frequency.

The principle of operation of the vestibular apparatus

The structure and functions of the auditory analyzer are not limited to the perception and processing of sounds; it plays important role throughout motor activity person. The fluids that fill part of the inner ear are responsible for the functioning of the vestibular apparatus, on which coordination of movements depends. The main role here is played by the endolymph; it works on the principle of a gyroscope. The slightest tilt of the head causes it to move, which, in turn, causes the otoliths to move, which irritate the hairs of the ciliated epithelium. With the help of complex neural connections, all this information is transmitted to parts of the brain, and then its work begins to coordinate and stabilize movements and balance.

The principle of coordinated operation of all chambers of the ear and brain, the transformation of sound vibrations into information

The structure and functions of the auditory analyzer, which can be briefly studied above, are aimed not just at capturing sounds of a certain frequency, but at converting them into information understandable by the human consciousness. All transformation work consists of the following main stages:

  1. Catching sounds and moving them along the ear canal, stimulating the eardrum to vibrate.
  2. Vibration of the three auditory ossicles of the inner ear caused by vibrations of the eardrum.
  3. Fluid movement in the inner ear and vibrations of hair cells.
  4. Converting vibrations into electrical impulses for their further transmission along the auditory nerves.
  5. Promotion of impulses along the auditory nerve to parts of the brain and converting them into information.

Auditory cortex and information analysis

No matter how well-functioning and ideal the work of all parts of the ear would be, everything would be meaningless without the functions and work of the brain, which converts all sound waves into information and guidance for action. The first thing a sound encounters on its way is the auditory cortex, located in the superior temporal gyrus of the brain. Here are the neurons that are responsible for the perception and separation of all ranges of sound. If, due to any brain damage, such as a stroke, these parts are damaged, the person may become hard of hearing or completely lose hearing and the ability to perceive speech.

Age-related changes and features in the functioning of the auditory analyzer

As a person ages, the operation of all systems, structure, functions and age characteristics auditory analyzers are no exception. Older people often experience hearing loss, which is considered physiological, i.e. normal. This is not considered a disease, but only age-related changes called persbycusis, which does not need to be treated, but can only be corrected with the help of special hearing aids.

Highlight a whole series reasons why hearing loss is possible in people who have reached a certain age threshold:

  1. Changes in the outer ear - thinning and sagging of the auricle, narrowing and curvature of the ear canal, loss of its ability to transmit sound waves.
  2. Thickening and clouding of the eardrum.
  3. Reduced mobility of the ossicular system of the inner ear, stiffness of their joints.
  4. Changes in the parts of the brain responsible for processing and perceiving sounds.

In addition to the usual functional changes at healthy person, problems can be aggravated by complications and consequences of previous otitis media; they can leave scars on the eardrum, which provoke problems in the future.

After medical scientists studied this important organ, as the auditory analyzer (structure and function), age-related deafness has ceased to be a global problem. Hearing aids, aimed at improving and optimizing the functioning of each department of the system, help older people live a full life.

Hygiene and care of human hearing organs

To keep your ears healthy, they, like the rest of your body, need timely and careful care. But, paradoxically, in half the cases problems arise precisely because of excessive care, and not because of its lack. The main reason is inept equipment ear sticks or other means for mechanical cleaning of accumulated sulfur, touching the tympanic septum, scratching it and the possibility of accidental perforation. To avoid such injuries, only clean the outside of the passage without using sharp objects.

To preserve your hearing in the future, it is better to follow the safety rules:

  • Limited listening to music using headphones.
  • Using special headphones and earplugs when working in noisy workplaces.
  • Protection against water getting into your ears while swimming in pools and ponds.
  • Prevention of otitis and colds ears in the cold season.

Understanding the operating principles of a hearing analyzer and following hygiene and safety rules at home or at work will help you preserve your hearing and not face the problem of hearing loss in the future.