The structure and functions of the human ear. What memory is the basis of sound knowledge? What is thinking

Satisfactory explanation of the phenomenon of hearing turned out to be extraordinary challenging task. A person who presented a theory explaining the perception of pitch and loudness of sound would almost certainly guarantee himself Nobel Prize.

original text(English)

Explaining hearing adequately has proven a singularly difficult task. One would almost ensure oneself a Nobel prize by presenting a theory explaining satisfactorily no more than the perception of pitch and loudness.

A. S. Reber, E. S. Reber

Hearing- ability biological organisms perceive sounds with the organs of hearing; special function of the hearing aid, excited by sound vibrations environment such as air or water. One of the biological distant sensations, also called acoustic perception. Provided by the auditory sensory system.

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General information

A person is able to hear sound ranging from 16 Hz to 20 kHz when transmitting vibrations through the air, and up to 220 kHz when transmitting sound through the bones of the skull. These waves are important biological significance, for example, sound waves in the range of 300-4000 Hz correspond to human voice. Sounds above 20,000 Hz are of little practical value, as they are quickly decelerated; vibrations below 60 Hz are perceived through the vibrational sense. The range of frequencies that humans can hear is called auditory or sound range ; higher frequencies are called ultrasonic, while lower frequencies are called infrasound.

Physiology of hearing

At the beginning of 2011, there were short message on the joint work of two Israeli institutions. IN human brain specialized neurons have been identified that allow assessing the pitch of a sound up to 0.1 tone. Animals, except for bats, do not possess such a device, and for different types accuracy is limited to 1/2 to 1/3 octaves. (Attention! This information requires clarification!)

Theories of the physiology of hearing

To date, there is no single reliable theory that explains all aspects of human perception of sound. Here are some of them:

• string theory by Helmholtz;
• Bekesy's theory of traveling wave;
• microphone theory;
• electromechanical theory.

Since a reliable theory of hearing has not been developed, psychoacoustic models based on data from studies conducted on various people are used in practice.

Hearing traces, fusion of auditory sensations

Experience shows that the sensation caused by a short sound impulse continues for some time after the sound stops. Therefore, two fairly fast successive sounds give a single auditory sensation, which is the result of their merging. As in visual perception, when individual images, replacing each other with a frequency of ≈ 16 frames / sec and higher, merge into a smoothly flowing movement, a sinusoidal pure sound is obtained as a result of the merging of individual oscillations with a repetition rate equal to the lower threshold of hearing sensitivity, that is, ≈ 16 Hz. The fusion of auditory sensations has great value for clarity of perception of sounds and in matters of consonance and dissonance, which play a huge role in music.

Projection of auditory sensations

No matter how they arise auditory sensations, we usually relate them to the external world, and therefore we always look for the reason for the excitation of our hearing in the vibrations received from the outside from one distance or another. This feature is much less pronounced in the sphere of hearing than in the sphere of visual sensations, which are distinguished by their objectivity and strict spatial localization and are probably also acquired through long experience and control of other senses. With auditory sensations, the ability to project, objectify, and spatially localize cannot reach such high degrees as with visual sensations. This is due to such features of the structure of the auditory apparatus, such as, for example, the lack of muscular mechanisms, depriving it of the possibility of accurate spatial determinations. We know the great importance that the muscular feeling has in all spatial definitions.

Judgments about the distance and direction of sounds

Our judgments about the distance at which sounds are emitted are very inaccurate, especially if a person's eyes are closed and he does not see the source of sounds and surrounding objects, by which one can judge the "acoustics environment" based on life experience, or the acoustics of the environment is atypical: for example, in an acoustic anechoic chamber, the voice of a person who is only a meter away from the listener seems to the latter many times and even tens of times more distant. Also, familiar sounds seem closer to us the louder they are, and vice versa. Experience shows that we are less mistaken in determining the distance of noises than musical tones. A person’s ability to judge the direction of sounds is very limited: not having movable and easy-to-collect sounds of the ear shells, in cases of doubt, he resorts to head movements and puts it in a position in which sounds are distinguished in the best way, that is, the sound is localized by a person in that direction , from which it is heard stronger and "clearer".

Three mechanisms are known by which the direction of sound can be distinguished:

• Difference in average amplitude (historically the first principle discovered): For frequencies above 1 kHz, i.e., those with a wavelength smaller than the size of the listener's head, the sound reaching the near ear has a greater intensity.
• Phase difference: branching neurons are able to distinguish between a phase shift of up to 10-15 degrees between the arrival of sound waves in the right and left ear for frequencies in the approximate range of 1 to 4 kHz (corresponding to an accuracy of 10 µs in determining the time of arrival).
• The difference in the spectrum: the folds of the auricle, the head and even the shoulders introduce small frequency distortions into the perceived sound, absorbing various harmonics in different ways, which is interpreted by the brain as Additional Information about horizontal and vertical localization of sound.

The ability of the brain to perceive the described differences in sound heard by the right and left ear led to the creation of binaural recording technology.

The described mechanisms do not work in water: determining the direction by the difference in loudness and spectrum is impossible, since the sound from the water passes almost without loss directly to the head, and therefore to both ears, which is why the volume and spectrum of sound in both ears at any location of the source sound with high fidelity are the same; determining the direction of the sound source by phase shift is impossible, because due to the much higher speed of sound in water, the wavelength increases several times, which means that the phase shift decreases many times.

From the description of the above mechanisms, the reason for the impossibility of determining the location of low-frequency sound sources is also clear.

Hearing study

Hearing is tested using a special device or computer program called an "audiometer".

It is possible to determine the leading ear using special tests. For example, different audio signals (words) are fed into the headphones, and a person fixes them on paper. From which ear there are more correctly recognized words, then the leading [ ] .

Define and frequency characteristics hearing, which is important when staging speech in hearing-impaired children.

Norm

Perception frequency range 16 Hz - 20 kHz changes with age - high frequencies are no longer perceived. The reduction in the range of audible frequencies is associated with changes in inner ear(cochlea) and the development of sensorineural hearing loss with age.

hearing threshold

hearing threshold- the minimum sound pressure at which the sound of a given frequency is perceived by the human ear. The threshold of hearing is expressed in decibels. The sound pressure of 2 10 −5 Pa at a frequency of 1 kHz was taken as the zero level. The hearing threshold for a particular person depends on individual properties, age, and physiological state.

Threshold of pain

auditory pain threshold- the value of sound pressure at which pain occurs in the auditory organ (which is associated, in particular, with the achievement of the stretch limit eardrum). Exceeding this threshold results in acoustic trauma. pain sensation defines the limit of the dynamic range of human hearing, which averages 140 dB for a tone signal and 120 dB for continuous spectrum noise.

When transmitting vibrations through the air, and up to 220 kHz when transmitting sound through the bones of the skull. These waves have important biological significance, for example, sound waves in the range of 300-4000 Hz correspond to the human voice. Sounds above 20,000 Hz are of little practical value, as they are quickly decelerated; vibrations below 60 Hz are perceived through the vibrational sense. The range of frequencies that humans can hear is called auditory or sound range; higher frequencies are called ultrasonic, while lower frequencies are called infrasound.

Physiology of hearing

The ability to distinguish sound frequencies is highly dependent on a particular person: his age, gender, susceptibility to auditory diseases, training and hearing fatigue. Individuals are able to perceive sound up to 22 kHz, and possibly even higher.

Some animals can hear sounds that are not audible to humans (ultrasound or infrasound). Bats use ultrasound for echolocation during flight. Dogs are able to hear ultrasound, which is the basis for the work of silent whistles. There is evidence that whales and elephants can use infrasound to communicate.

A person can distinguish several sounds at the same time due to the fact that there can be several standing waves in the cochlea at the same time.

To satisfactorily explain the phenomenon of hearing has proved to be an extraordinarily difficult task. A person who came up with a theory that would explain the perception of pitch and loudness of sound would almost certainly guarantee himself a Nobel Prize.

original text(English)

Explaining hearing adequately has proven a singularly difficult task. One would almost ensure oneself a Nobel prize by presenting a theory explaining satisfactorily no more than the perception of pitch and loudness.

- Reber, Arthur S., Reber (Roberts), Emily S. The Penguin Dictionary of Psychology. - 3rd edition. - London: Penguin Books Ltd, . - 880 p. - ISBN 0-14-051451-1, ISBN 978-0-14-051451-3

At the beginning of 2011, a brief report about the joint work of the two Israeli institutes was published in separate scientific media. In the human brain, specialized neurons have been isolated that allow one to estimate the pitch of a sound, up to 0.1 tone. Animals other than bats do not possess such a device, and for different species the accuracy is limited from 1/2 to 1/3 octaves. (Attention! This information requires clarification!)

Psychophysiology of hearing

Projection of auditory sensations

No matter how auditory sensations arise, we usually refer them to the external world, and therefore we always look for the reason for the excitation of our hearing in vibrations received from the outside from one distance or another. This feature is much less pronounced in the sphere of hearing than in the sphere of visual sensations, which are distinguished by their objectivity and strict spatial localization and are probably also acquired through long experience and control of other senses. With auditory sensations, the ability to project, objectify and spatially localize cannot reach such high degrees as with visual sensations. This is due to such features of the structure of the auditory apparatus, such as, for example, the lack of muscular mechanisms, depriving it of the possibility of accurate spatial determinations. We know the great importance muscle feeling in all spatial definitions.

Judgments about the distance and direction of sounds

Our judgments about the distance at which sounds are emitted are very inaccurate, especially if the person's eyes are closed and he does not see the source of the sounds and the surrounding objects, by which one can judge the "acoustics of the environment" based on life experience, or the acoustics of the environment are atypical: so , for example, in an acoustic anechoic chamber, the voice of a person who is only a meter away from the listener seems to the latter many times and even tens of times more distant. Also, familiar sounds seem closer to us the louder they are, and vice versa. Experience shows that we are less mistaken in determining the distance of noises than musical tones. A person’s ability to judge the direction of sounds is very limited: not having auricles that are mobile and convenient for collecting sounds, in cases of doubt, he resorts to head movements and puts it in a position in which sounds differ in the best way, that is, the sound is localized by a person in that direction , from which it is heard stronger and "clearer".

Three mechanisms are known by which the direction of sound can be distinguished:

• Difference in average amplitude (historically the first principle to be discovered): For frequencies above 1 kHz, that is, those with a wavelength smaller than the size of the listener's head, the sound reaching the near ear has a greater intensity.
• Phase Difference: Branching neurons are able to distinguish phase shifts of up to 10-15 degrees between the arrival of sound waves in the right and left ear for frequencies in the approximate range of 1 to 4 kHz (corresponding to an accuracy of 10 µs in timing of arrival).
• The difference in the spectrum: the folds of the auricle, the head and even the shoulders introduce small frequency distortions into the perceived sound, absorbing different harmonics in different ways, which is interpreted by the brain as additional information about the horizontal and vertical localization of the sound.

The ability of the brain to perceive the described differences in the sound heard by the right and left ear led to the creation of binaural recording technology.

The described mechanisms do not work in water: determining the direction by the difference in loudness and spectrum is impossible, since the sound from the water passes almost without loss directly to the head, and therefore to both ears, which is why the volume and spectrum of sound in both ears at any location of the source sound with high fidelity are the same; determining the direction of the sound source by phase shift is impossible, because due to the much higher speed of sound in water, the wavelength increases several times, which means that the phase shift decreases many times.

From the description of the above mechanisms, the reason for the impossibility of determining the location of low-frequency sound sources is also clear.

Hearing study

Hearing is tested using a special device or computer program called an "audiometer".

The frequency characteristics of hearing are also determined, which is important when staging speech in hearing-impaired children.

Norm

The perception of the frequency range 16 Hz - 22 kHz changes with age - high frequencies are no longer perceived. A decrease in the range of audible frequencies is associated with changes in the inner ear (cochlea) and with the development of sensorineural hearing loss with age.

hearing threshold

hearing threshold- the minimum sound pressure at which the sound of a given frequency is perceived by the human ear. The threshold of hearing is expressed in decibels. The sound pressure of 2 10 −5 Pa at a frequency of 1 kHz was taken as the zero level. The hearing threshold for a particular person depends on individual properties, age, and physiological state.

Threshold of pain

auditory pain threshold- the value of sound pressure at which pain occurs in the auditory organ (which is associated, in particular, with the achievement of the tympanic membrane extensibility limit). Exceeding this threshold results in acoustic trauma. The sensation of pain defines the limit of the dynamic range of human audibility, which averages 140 dB for a tone signal and 120 dB for noise with a continuous spectrum.

Pathology

see also

• auditory hallucination
• Auditory nerve

Literature

Physical Encyclopedic Dictionary / Ch. ed. A. M. Prokhorov. Ed. collegium D. M. Alekseev, A. M. Bonch-Bruevich, A. S. Borovik-Romanov and others - M .: Sov. Encycl., 1983. - 928 p., p. 579

Links

• Video lecture Auditory perception

Wikimedia Foundation. 2010 .

See what "Hearing" is in other dictionaries:

hearing- hearing, and ... Russian spelling dictionary

hearing- hearing / ... Morphemic spelling dictionary

Exist., m., use. often Morphology: (no) what? hearing and hearing, what? hearing, (seeing) what? hearing what? hearing about what? about hearing; pl. What? rumors, (no) what? rumors for what? rumors, (see) what? rumors what? rumors about what? about rumors perception by organs ... ... Dictionary Dmitrieva

Husband. one of the five senses by which sounds are recognized; instrument is his ear. Hearing dull, thin. In deaf and deaf animals, hearing is replaced by a sense of concussion. Go by ear, seek by ear. | A musical ear, an inner feeling that comprehends mutual ... ... Dahl's Explanatory Dictionary

Hearing, m. 1. only units. One of the five external senses, giving the ability to perceive sounds, the ability to hear. The ear is the organ of hearing. Acute hearing. A hoarse cry reached his ears. Turgenev. “I wish glory, so that your hearing will be amazed by my name ... Explanatory Dictionary of Ushakov

Despite the fact that we receive most of the information about the world around us through vision, it was hearing that played the most important role in the formation of centers of perception, analysis and speech synthesis. human language. If a person were deaf, then our civilization would not exist, since all of it is based on previously accumulated knowledge. At present, this knowledge is transmitted using written information, but we forget that without language it would be impossible to create any alphabet and writing. And language, in turn, is impossible without the work of the organ of hearing. After all, the temporal cortex, the higher and subcortical hearing centers perceive their own spoken words. And in this sense, the meaning of hearing is much more than just a person's orientation in nature. What is the structure of the organ of hearing?

There is a simple example: at the sudden sound of a shot, a person always blinks involuntarily. There is no other way to explain this reflex, as by direct switching of sensory neurons from the subcortical center of hearing analysis to motor neurons leading to the nuclei facial nerve, which innervates the mimic muscles of the face, as well as the circular muscle of the eye, which protects the eyes from possible damage. But this example refers to the anatomy of the central nervous system. How is the human ear structured?

The human hearing organ is a structure that reflects the external sense. It is represented by three sections: the outer (periphery), middle, and inner (labyrinth) ear. The boundaries of these three departments are clearly marked, and each of the departments has its own function. Let's briefly describe anatomical structure each of the departments.

Outer parts of the ear

The structure of the organ of hearing usually begins to be studied from the outer ear. The outer ear is the outer part of the auditory organ, and is represented by:

• the auricle, which is cartilage covered with skin on top;
• external auditory meatus, which has cartilaginous outer and bone tissue.

The peripheral (outer) ear ends with a kind of barrier that captures sounds. It resembles a membrane and is called the tympanic membrane. This structure is the lateral or lateral border of the tympanic space, or cavity, located inside the pyramid of the temporal bone. It is a barrier that separates the outer and middle ear.

Middle ear

The middle ear lies completely within the temporal bone. This is a tympanic cavity, which occupies a small volume. It contains a chain of miniature auditory ossicles. The structures of this department also include auditory tube. It is also called Eustachian, and it serves to ensure that the air from oral cavity freely penetrated into the cavity of the middle ear, and equalized the pressure indicators outside and inside. In the event that the pressure is different, then the conduction of sound vibrations along the chain of bones to the inner ear will be disturbed.

The chain of auditory ossicles is located in the direction from the membrane to the cochlea, and they are the smallest bones in the human body. They are named according to their shape:

• hammer;
• anvil;
• stapes.

The structure of the auditory ossicles is such that they form the two smallest joints in human body that have flexible mobility. In addition to the chain of bones, in the cavity of the middle ear, which is no more than one cubic centimeter in volume, there are two small muscles.

They maintain the desired tension of the tympanic membrane, create a tone in the sound ossicles chain, help the sound-conducting apparatus to adapt to fluctuations of different loudness and protect the cochlea from excessive stimuli. The meaning of the existence of the auditory ossicles is the transmission of vibration from the tympanic membrane from the outside to the inside, to the oval window of the vestibule. This is the entrance to the cochlea where sound waves are analyzed (a labyrinth located in the structure of the inner ear).

inner ear

The inner ear, or labyrinth, is otherwise called the vestibulocochlear organ. The structure of the hearing organ in this section is more complex: it is a peripheral analyzer of attraction, or gravity, together with balance, and a cochlea, or an analyzer of sounds. In humans, they are represented by two separate structures, but at the same time they are interconnected.

The direct structure that perceives elastic sound waves propagating in the air is a spiral organ. Inside the spiral organ there are about 24,000 different auditory strings, which are very small, and are stretched around the inside of the cochlea. Those that resonate in response to low vibrations are longer and thicker, while those that resonate in response to high frequencies are shorter and thinner. Such anatomy is characteristic of all mammals, and differs only in the location, number and gauge of the strings. All auditory strings are located inside the endolymph, a special, transparent fluid, to which the vibrations of the chain of auditory ossicles are transmitted. As a result of the vibration of the strings, a weak electricity Thus, the cochlea functions as a microphone that recognizes various vibrations.

Functions of the organ of hearing

What are the functions of the human ear? The simplest function is in the outer ear. This design is nothing more than a device for passively capturing sound waves and transmitting them to an elastic membrane called the eardrum. The ear also protects the ear canal. Inside it, a special exocrine secret is produced, which is called earwax. Earwax protects the eardrum, it must not become moist and swell, otherwise it will not conduct sound well. Therefore, sulfur prevents its wetting during washing.

The middle ear appeared only when life on earth came to land, and the air became the main medium for the propagation of sound. The function of the middle ear is to transmit sound waves from the elastic membrane, or tympanic membrane, to the chain of ossicles - transmitters, and then to the cochlea. In other words, the middle ear is designed to ensure that the signal from the air, caught by the outer ear and falling on the membrane, is already transmitted through a reliable system of bones, that is, it passes into a dense (bone) environment. Sound waves propagate faster in the ossicular chain than in air.

The function of the labyrinth is the transmission of sound to the elastic fluid, or endolymph, the analysis of vibrations, and the excitation of an electric current. This electrical current is an afferent nerve impulse that ascends into the central nervous system as part of a special nerve.

Diseases of the organ of hearing

The complex function of the auditory organ can be disturbed in its different departments. The most common are purulent-inflammatory and dystrophic degenerative diseases. An example inflammatory diseases are otitis media, for example, acute purulent otitis media, and an example of a dystrophic degenerative process is sensorineural hearing loss.

Modern man is often in an aggressive sound environment. Various industrial sounds, the noise of subway trains and aircraft engines, loud music, low frequency sources such as subwoofers can cause not only hearing damage, but also neurological diseases. Therefore, to avoid increased load on the human hearing organ, you need to check it regularly. To do this, you can simply visit an ENT - a doctor who, using the test of whispered speech and special tables, will determine the acuity of hearing, and the ability to distinguish between different frequencies. IN doubtful cases apply more serious methods such as audiometry.

Human hearing

Hearing- the ability of biological organisms to perceive sounds with the organs of hearing; a special function of the hearing aid that is excited by the sound vibrations of the environment, such as air or water. One of the biological distant sensations, also called acoustic perception. Provided by the auditory sensory system.

Human hearing is able to hear sound ranging from 16 Hz to 22 kHz when transmitting vibrations through the air, and up to 220 kHz when transmitting sound through the bones of the skull. These waves have important biological significance, for example, sound waves in the range of 300-4000 Hz correspond to the human voice. Sounds above 20,000 Hz are of little practical value, as they are quickly decelerated; vibrations below 60 Hz are perceived through the vibrational sense. The range of frequencies that a person is able to hear is called the auditory or sound range; higher frequencies are called ultrasound and lower frequencies are called infrasound.

The ability to distinguish audio frequencies strongly depends on a particular person: his age, gender, heredity, susceptibility to diseases of the organ of hearing, fitness and hearing fatigue. Some people are able to perceive sounds relatively high frequency- up to 22 kHz, and possibly higher.
In humans, as in most mammals, the organ of hearing is the ear. In a number of animals, auditory perception is carried out through a combination of various organs, which may differ significantly in their structure from the ear of mammals. Some animals are able to perceive acoustic vibrations that are not audible to humans (ultrasound or infrasound). The bats During flight, they use ultrasound for echolocation. Dogs are able to hear ultrasound, which is the basis for the work of silent whistles. There is evidence that whales and elephants can use infrasound to communicate.
A person can distinguish several sounds at the same time due to the fact that there can be several sounds in the cochlea at the same time. standing waves.

The mechanism of the auditory system:

An audio signal of any nature can be described by a certain set of physical characteristics:
frequency, intensity, duration, temporal structure, spectrum, etc.

They correspond to certain subjective sensations arising from the perception of sounds by the auditory system: loudness, pitch, timbre, beats, consonances-dissonances, masking, localization-stereoeffect, etc.
Auditory sensations are associated with physical characteristics in an ambiguous and non-linear way, for example, the loudness depends on the intensity of the sound, on its frequency, on the spectrum, etc. Even in the last century, Fechner's law was established, which confirmed that this relationship is non-linear: "Sensations
proportional to the ratio of the logarithms of the stimulus. "For example, the sensations of a change in loudness are primarily associated with a change in the logarithm of intensity, pitch - with a change in the logarithm of frequency, etc.

All sound information that a person receives from the outside world (it is approximately 25% of the total), he recognizes with the help of the auditory system and work higher departments brain, translates into the world of its sensations, and decides how to respond to it.
Before proceeding to the study of the problem of how the auditory system perceives pitch, let us briefly dwell on the mechanism of the auditory system.
Many new and very interesting results have now been obtained in this direction.
The auditory system is a kind of receiver of information and consists of the peripheral part and the higher parts of the auditory system. The most studied transformation processes sound signals in the peripheral part of the auditory analyzer.

peripheral part

This is an acoustic antenna that receives, localizes, focuses and amplifies the sound signal;
- microphone;
- frequency and time analyzer;
- analog-to-digital converter that converts analog signal into binary nerve impulses - electrical discharges.

A general view of the peripheral auditory system is shown in the first figure. The peripheral auditory system is usually divided into three parts: external, middle, and inner ear.

outer ear consists of the auricle and auditory canal ending in a thin membrane called the tympanic membrane.
The external ears and head are components of the external acoustic antenna that connects (matches) the eardrum to the external sound field.
The main functions of the outer ears are binaural (spatial) perception, localization of a sound source and amplification of sound energy, especially in the medium and high frequencies.

auditory canal is a curved cylindrical tube 22.5 mm long, which has a first resonant frequency of about 2.6 kHz, so in this frequency range it significantly amplifies the sound signal, and it is here that the region of maximum hearing sensitivity is located.

Eardrum - a thin film with a thickness of 74 microns, has the form of a cone facing the tip towards the middle ear.
At low frequencies, it moves like a piston, at higher frequencies, it forms a complex system nodal lines, which is also important for sound amplification.

Middle ear- an air-filled cavity connected to the nasopharynx by the Eustachian tube to equalize atmospheric pressure.
When atmospheric pressure changes, air can enter or exit the middle ear, so the eardrum does not respond to slow changes in static pressure - up and down, etc. There are three small auditory ossicles in the middle ear:
hammer, anvil and stirrup.
The malleus is attached to the tympanic membrane at one end, the other end is in contact with the anvil, which is connected to the stirrup by a small ligament. The base of the stirrup is connected to the oval window into the inner ear.

Middle ear performs the following functions:
impedance matching air environment with the liquid medium of the cochlea of ​​the inner ear; defence from loud sounds(acoustic reflex); amplification (lever mechanism), due to which the sound pressure transmitted to the inner ear is increased by almost 38 dB compared to that which enters the eardrum.

inner ear located in the labyrinth of canals in the temporal bone, and includes the organ of balance ( vestibular apparatus) and a snail.

Snail(cochlea) plays a major role in auditory perception. It is a tube of variable cross section, folded three times like a snake's tail. In the unfolded state, it has a length of 3.5 cm. Inside, the snail has an extremely complex structure. Along its entire length, it is divided by two membranes into three cavities: the scala vestibuli, the median cavity and the scala tympani.

Conversion of mechanical oscillations of the membrane into discrete electrical impulses nerve fibers occur in the organ of Corti. When the basilar membrane vibrates, the cilia on the hair cells flex and this generates an electrical potential, which causes a flow of electrical nerve impulses carrying all necessary information about the incoming sound signal to the brain for further processing and response.

The higher parts of the auditory system (including the auditory cortex) can be considered as a logical processor that extracts (decodes) useful sound signals against the background of noise, groups them according to certain characteristics, compares them with the images in memory, determines their informational value and decides on response actions.

The receptive part of the auditory analyzer is the ear, the conductive part is the auditory nerve, the central part is the auditory zone of the cerebral cortex. The organ of hearing consists of three sections: the outer, middle and inner ear. The ear includes not only the actual organ of hearing, through which auditory sensations are perceived, but also the organ of balance, due to which the body is held in a certain position.

The outer ear consists of the auricle and the external auditory meatus. The shell is formed by cartilage covered on both sides with skin. With the help of a shell, a person picks up the direction of the sound. The muscles that move the auricle are rudimentary in humans. The external auditory meatus looks like a tube 30 mm long, lined with skin, in which there are special glands that secrete earwax. In depth, the ear canal is tightened by a thin tympanic membrane oval shape. On the side of the middle ear, in the middle of the tympanic membrane, the handle of the malleus is strengthened. The membrane is elastic; when sound waves strike, it repeats these vibrations without distortion.

The middle ear is represented tympanic cavity, which communicates with the nasopharynx with the help of the auditory (Eustachian) tube; it is delimited from the outer ear by the tympanic membrane. The components of this department are hammer, anvil And stapes. With its handle, the hammer fuses with the eardrum, while the anvil is articulated with both the hammer and the stirrup, which covers oval hole leading to the inner ear. In the wall separating the middle ear from the inner ear, except oval window there is also a round window covered with a membrane.
The structure of the organ of hearing:
1 - Auricle, 2 - external auditory meatus,
3 - tympanic membrane, 4 - middle ear cavity, 5 - auditory tube, 6 - cochlea, 7 - semicircular canals, 8 - anvil, 9 - hammer, 10 - stapes

The inner ear, or labyrinth, is located in the thickness of the temporal bone and has double walls: membranous labyrinth as if inserted into bone, repeating its shape. The gap between them is filled clear liquid - perilymph, cavity of the membranous labyrinth endolymph. Labyrinth Presented the threshold anterior to it is the cochlea, posterior - semicircular canals. The cochlea communicates with the middle ear cavity through a round window covered with a membrane, and the vestibule through the oval window.

The organ of hearing is the cochlea, the rest of its parts are the organs of balance. The cochlea is a spiral canal of 2 3/4 turns, separated by a thin membranous septum. This membrane is spirally curled and is called basic. It consists of fibrous tissue, including about 24 thousand special fibers (auditory strings) different lengths and located across along the entire course of the cochlea: the longest - at its top, at the base - the most shortened. Above these fibers hang auditory hair cells - receptors. This is the peripheral end of the auditory analyzer, or organ of Corti. The hairs of the receptor cells face the cavity of the cochlea - the endolymph, and the auditory nerve originates from the cells themselves.

Perception of sound stimuli. sound waves, passing through the external auditory canal, cause vibrations of the eardrum and are transmitted auditory ossicles, and from them - to the membrane of the oval window leading to the vestibule of the cochlea. The resulting oscillation sets in motion the perilymph and endolymph of the inner ear and is perceived by the fibers of the main membrane, which carries the cells of the organ of Corti. High-pitched sounds with a high oscillation frequency are perceived by short fibers located at the base of the cochlea and are transmitted to the hairs of the cells of the organ of Corti. In this case, not all cells are excited, but only those that are on fibers of a certain length. Consequently, the primary analysis of sound signals begins already in the organ of Corti, from which excitation along the fibers auditory nerve transmitted to the auditory center of the cerebral cortex in the temporal lobe, where their qualitative assessment takes place.

vestibular apparatus. The vestibular apparatus plays an important role in determining the position of the body in space, its movement and speed of movement. It is located in the inner ear and consists of vestibule and three semicircular canals placed in three mutually perpendicular planes. The semicircular canals are filled with endolymph. There are two sacs in the endolymph of the vestibule - round And oval with special lime stones - statoliths, adjacent to hair sac receptor cells.

In the normal position of the body, the statoliths irritate the hairs of the lower cells with their pressure; when the position of the body changes, the statoliths also move and irritate other cells with their pressure; the received impulses are transmitted to the cerebral cortex. In response to irritation of the vestibular receptors associated with the cerebellum and the motor zone of the cerebral hemispheres, the muscle tone and position of the body in space reflexively change. Three semicircular canals depart from the oval sac, which initially have extensions - ampoules, in which there are hair cells - receptors. Since the channels are located in three mutually perpendicular planes, the endolymph in them, when the position of the body changes, irritates certain receptors, and the excitation is transmitted to the corresponding parts of the brain. The body reflexively responds necessary change body position.

Hearing hygiene. In outdoor ear canal accumulates earwax, dust and microorganisms linger on it, so you need to regularly wash your ears with warm soapy water; under no circumstances should sulfur be removed hard objects. Overwork of the nervous system and overstrain of hearing can cause harsh sounds and noises. Prolonged noise is especially harmful, and hearing loss and even deafness occur. Loud noise reduces labor productivity up to 40-60%. To combat noise in production conditions, wall and ceiling cladding with special sound-absorbing materials, individual anti-noise headphones are used. Motors and machine tools are installed on foundations that muffle the noise from the shaking of mechanisms.