(Auditory sensory system)
Lecture questions:
1. Structural and functional characteristics of the auditory analyzer:
a. Outer ear
b. Middle ear
c. Inner ear
2. Divisions of the auditory analyzer: peripheral, conductive, cortical.
3. Perception of height, sound intensity and sound source location:
a. Basic electrical phenomena in the cochlea
b. Perception of sounds of different pitches
c. Perception of sounds of varying intensities
d. Identifying the sound source (binaural hearing)
e. Auditory adaptation
1. The auditory sensory system is the second most important distant human analyzer; it plays an important role in humans in connection with the emergence of articulate speech.
Hearing analyzer function: transformation sound waves into the energy of nervous excitation and auditory sensation.
Like any analyzer, the auditory analyzer consists of a peripheral, conductive and cortical section.
PERIPHERAL DEPARTMENT
Converts the energy of sound waves into energy nervous excitation – receptor potential (RP). This department includes:
· inner ear (sound-receiving apparatus);
· middle ear (sound-conducting apparatus);
· outer ear (sound-collecting apparatus).
The components of this department are combined into the concept organ of hearing.
Functions of the organs of hearing
Outer ear:
a) collecting sound (auricle) and directing the sound wave into the external auditory canal;
b) carrying out sound wave through the ear canal to the eardrum;
c) mechanical protection and protection from environmental temperature influences of all other parts of the hearing organ.
Middle ear(sound-conducting section) is the tympanic cavity with 3 auditory ossicles: the malleus, the incus and the stapes.
The eardrum separates the external auditory canal from the tympanic cavity. The handle of the malleus is woven into the eardrum, its other end is articulated with the incus, which, in turn, is articulated with the stapes. The stapes is adjacent to the membrane of the oval window. The pressure in the tympanic cavity is equal to atmospheric pressure, which is very important for adequate perception of sounds. This function is performed by the Eustachian tube, which connects the middle ear cavity to the pharynx. When swallowing, the tube opens, resulting in ventilation of the tympanic cavity and equalization of the pressure in it with atmospheric pressure. If external pressure changes rapidly (rapid rise to altitude), and swallowing does not occur, then the pressure difference between atmospheric air and air in the tympanic cavity leads to tension of the eardrum and the occurrence of unpleasant sensations (“stuck ears”), and a decrease in the perception of sounds.
The area of the tympanic membrane (70 mm2) is significantly larger than the area of the oval window (3.2 mm2), due to which gain the pressure of sound waves on the membrane of the oval window is 25 times. Lever mechanism of bones reduces the amplitude of sound waves is 2 times, so the same amplification of sound waves occurs at the oval window of the tympanic cavity. Consequently, the middle ear amplifies sound by about 60-70 times, and if we take into account the amplifying effect of the outer ear, then this value increases by 180-200 times. In this regard, during strong sound vibrations, in order to prevent the destructive effect of sound on the receptor apparatus of the inner ear, the middle ear reflexively turns on “ defense mechanism" It consists of the following: in the middle ear there are 2 muscles, one of them stretches the eardrum, the other fixes the stapes. Under strong sound impacts, these muscles, when contracting, limit the amplitude of vibration of the eardrum and fix the stapes. This “quenches” the sound wave and prevents excessive stimulation and destruction of the phonoreceptors of the organ of Corti.
Inner ear: represented by the cochlea - a spirally twisted bone canal (2.5 turns in humans). This channel is divided along its entire length into three narrow parts (ladders) with two membranes: the main membrane and the vestibular membrane (Reisner).
On the main membrane there is a spiral organ - the organ of Corti (organ of Corti) - this is the actual sound-receiving apparatus with receptor cells - this is the peripheral section of the auditory analyzer.
The helicotrema (orifice) connects the superior and inferior canals at the apex of the cochlea. The middle channel is separate.
Above the organ of Corti is a tectorial membrane, one end of which is fixed and the other remains free. The hairs of the outer and inner hair cells of the organ of Corti come into contact with the tectorial membrane, which is accompanied by their excitation, i.e. the energy of sound vibrations is transformed into the energy of the excitation process.
Structure of the organ of Corti
The transformation process begins with sound waves entering the outer ear; they move the eardrum. Vibrations of the tympanic membrane through the system of auditory ossicles of the middle ear are transmitted to the membrane of the oval window, which causes vibrations of the perilymph of the scala vestibularis. These vibrations are transmitted through the helicotrema to the perilymph of the scala tympani and reach the round window, protruding it towards the middle ear (this prevents the sound wave from dying out when passing through the vestibular and tympanic canal of the cochlea). Vibrations of the perilymph are transmitted to the endolymph, which causes vibrations of the main membrane. The fibers of the basilar membrane begin to vibrate together with the receptor cells (outer and inner hair cells) of the organ of Corti. In this case, the phonoreceptor hairs come into contact with the tectorial membrane. The cilia of the hair cells are deformed, this causes the formation of a receptor potential, and on its basis an action potential (nerve impulse), which is carried along the auditory nerve and transmitted to the next section of the auditory analyzer.
CONDUCTING DEPARTMENT OF THE HEARING ANALYZER
The conductive section of the hearing analyzer is presented auditory nerve. It is formed by the axons of neurons of the spiral ganglion (1st neuron of the pathway). The dendrites of these neurons innervate the hair cells of the organ of Corti (afferent link), the axons form the fibers of the auditory nerve. The auditory nerve fibers end on the neurons of the nuclei of the cochlear body (VIII pair of h.m.n.) (second neuron). Then, after partial decussation, the fibers of the auditory pathway go to the medial geniculate body of the thalamus, where switching occurs again (third neuron). From here, excitation enters the cortex (temporal lobe, superior temporal gyrus, transverse gyri of Heschl) - this is the projection auditory zone of the cortex.
CORTICAL DIVISION OF THE AUDITORY ANALYZER
Presented in the temporal lobe of the cerebral cortex - superior temporal gyrus, transverse temporal gyri of Heschl. Cortical gnostic auditory zones are associated with this projection zone of the cortex - Wernicke's sensory speech area and praxial zone – Broca's speech motor center(inferior frontal gyrus). The cooperative activity of the three cortical zones ensures the development and function of speech.
The auditory sensory system has feedbacks, which provide regulation of the activity of all levels of the auditory analyzer with the participation of descending pathways that start from the neurons of the “auditory” cortex and sequentially switch in the medial geniculate bodies thalamus, inferior colliculi of the midbrain with the formation of tectospinal descending tracts and on the nuclei of the cochlear body of the medulla oblongata with the formation of vestibulospinal tracts. This ensures, in response to the action of a sound stimulus, the formation of a motor reaction: turning the head and eyes (and in animals, the ears) towards the stimulus, as well as increasing the tone of the flexor muscles (flexion of the limbs in the joints, i.e. readiness to jump or run ).
Auditory cortex
PHYSICAL CHARACTERISTICS OF SOUND WAVES THAT ARE PERCEIVED BY THE HEARING ORGAN
1. The first characteristic of sound waves is their frequency and amplitude.
The frequency of sound waves determines the pitch of the sound!
A person distinguishes sound waves with a frequency from 16 to 20,000 Hz (this corresponds to 10-11 octaves). Sounds whose frequency is below 20 Hz (infrasounds) and above 20,000 Hz (ultrasounds) by humans not felt!
Sound that consists of sinusoidal or harmonic vibrations is called tone(high frequency - high tone, low frequency - low tone). A sound consisting of unrelated frequencies is called noise.
2. The second characteristic of sound that the auditory sensory system distinguishes is its strength or intensity.
The strength of sound (its intensity) together with the frequency (tone of sound) is perceived as volume. The unit of loudness measurement is bel = lg I/I 0, but in practice it is more often used decibel (dB)(0.1 bel). A decibel is 0.1 decimal logarithm of the ratio of sound intensity to its threshold intensity: dB = 0.1 log I/I 0. The maximum volume level when sound causes pain is 130-140 dB.
The sensitivity of the auditory analyzer is determined by the minimum sound intensity that causes auditory sensations.
In the range of sound vibrations from 1000 to 3000 Hz, which corresponds to human speech, the ear has the greatest sensitivity. This set of frequencies is called speech zone(1000-3000 Hz). Absolute sound sensitivity in this range is 1*10 -12 W/m2. For sounds above 20,000 Hz and below 20 Hz, absolute hearing sensitivity decreases sharply - 1*10 -3 W/m2. In the speech range, sounds are perceived that have a pressure of less than 1/1000 of a bar (a bar is equal to 1/1,000,000 of normal atmospheric pressure). Based on this, in transmitting devices, in order to ensure adequate understanding of speech, information must be transmitted in the speech frequency range.
MECHANISM OF PERCEPTION OF HEIGHT (FREQUENCY), INTENSITY (STRENGTH) AND LOCALIZATION OF SOUND SOURCE (BINAURAL HEARING)
Perception of sound wave frequency
The receptive part of the auditory analyzer is the ear, the conductive part is the auditory nerve, and the central part is the auditory zone of the cerebral cortex. The hearing organ consists of three sections: the outer, middle and inner ear. The ear includes not only the organ of hearing itself, with the help of 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 pinna and the external auditory canal. The shell is formed by cartilage covered on both sides by skin. With the help of a shell, a person catches the direction of sound. The muscles that move the auricle are rudimentary in humans. The external auditory canal looks like a tube 30 mm long, lined with skin, in which there are special glands that secrete earwax. In the depths, the ear canal is covered with a thin oval-shaped eardrum. On the side of the middle ear, in the middle of the eardrum, the handle of the hammer is strengthened. The membrane is elastic; when struck by sound waves, it repeats these vibrations without distortion.
The middle ear is represented by the tympanic cavity, which communicates with the nasopharynx through the auditory (Eustachian) tube; It is delimited from the outer ear by the eardrum. The components of this department are: hammer, anvil And stapes. With its handle, the malleus fuses with the eardrum, while the anvil is articulated with both the malleus and the stirrup, which covers the oval hole leading to the inner ear. In the wall separating the middle ear from the inner ear, in addition to the oval window, there is also a round window covered with a membrane.
Structure of the hearing organ:
1 -
auricle, 2 - external auditory canal,
3 - eardrum, 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 temporal bone and has double walls: membranous labyrinth as if inserted into bone, repeating its shape. The gap-like space between them is filled clear liquid - perilymph, cavity of the membranous labyrinth - endolymph. Labyrinth presented the threshold anterior to it is the cochlea, posteriorly - semicircular canals. The cochlea communicates with the middle ear cavity through a round window covered by a membrane, and the vestibule communicates through the oval window.
The organ of hearing is the cochlea, its remaining parts make up the organs of balance. The cochlea is a spirally twisted 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, which includes about 24 thousand special fibers (auditory strings) of different lengths and located transversely along the entire course of the cochlea: the longest are at its apex, and the shortest at the base. Overhanging these fibers are 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 in the eardrum and are transmitted to the auditory ossicles, and from them to the membrane of the oval window leading to the vestibule of the cochlea. The resulting vibration 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 vibration frequency are perceived by short fibers located at the base of the cochlea and transmitted to the hairs of the cells of the organ of Corti. In this case, not all cells are excited, but only those located 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 of the auditory nerve is transmitted to the auditory center of the cerebral cortex in the temporal lobe, where their qualitative assessment occurs.
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, located in three mutually perpendicular planes. The semicircular canals are filled with endolymph. In the endolymph of the vestibule there are two sacs - round And oval with special lime stones - statolites, adjacent to the hair receptor cells of the sacs.
In normal body position, the statoliths irritate the hairs of the lower cells with their pressure; when the body position 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, muscle tone and body position in space reflexively change. Three semicircular canals extend from the oval sac, which initially have extensions - ampoules, in which hair cells - receptors are located. Since the channels are located in three mutually perpendicular planes, the endolymph in them, when the body position changes, irritates certain receptors, and the excitation is transmitted to the corresponding parts of the brain. The body reflexively responds with the necessary change in body position.
Hearing hygiene. Earwax accumulates in the external auditory canal and traps dust and microorganisms, so it is necessary to regularly wash your ears with warm soapy water; Under no circumstances should you remove sulfur with hard objects. Overfatigue of the nervous system and overstrain of hearing can cause sharp sounds and noises. Prolonged noise is especially harmful, causing hearing loss and even deafness. Loud noise reduces labor productivity by up to 40-60%. To combat noise in industrial environments, walls and ceilings are lined with special materials that absorb sound, and individual noise-reducing headphones are used. Motors and machines are installed on foundations that muffle the noise from the shaking of the mechanisms.
Human hearing is designed to capture a wide range of sound waves and transform them into electrical impulses to be sent to the brain for analysis. Unlike the vestibular apparatus associated with the organ of hearing, which functions normally almost from birth, hearing takes a long time to develop. The formation of the auditory analyzer ends no earlier than at 12 years of age, and the greatest hearing acuity is achieved by the age of 14-19 years. the auditory analyzer has three sections: the peripheral or organ of hearing (ear); conductive, including nerve pathways; cortical, located in the temporal lobe of the brain. Moreover, there are several auditory centers in the cerebral cortex. Some of them (the inferior temporal gyri) are designed to perceive simpler sounds - tones and noises, others are associated with the most complex sound sensations that arise when a person speaks, listens to speech or music.
Structure human ear The human auditory analyzer perceives sound waves with an oscillation frequency of 16 to 20 thousand per second (16-20000 hertz, Hz). The upper sound threshold for an adult is 20,000 Hz; lower threshold – ranging from 12 to 24 Hz. Children have a higher upper limit of hearing around 22,000 Hz; in older people, on the contrary, it is usually lower - about 15,000 Hz. The ear is most sensitive to sounds with frequencies ranging from 1000 to 4000 Hz. Below 1000 Hz and above 4000 Hz, the excitability of the hearing organ is greatly reduced. The ear is a complex vestibular-auditory organ. Like all our sense organs, the human hearing organ performs two functions. It perceives sound waves and is responsible for the position of the body in space and the ability to maintain balance. This is a paired organ that is located in the temporal bones of the skull, limited externally by the auricles. The receptor apparatus of the auditory and vestibular systems are located in the inner ear. The structure of the vestibular system can be viewed separately, but now let’s move on to a description of the structure of the parts of the hearing organ.
The organ of hearing consists of 3 parts: the outer, middle and inner ear, with the outer and middle ear playing the role of a sound-conducting apparatus, and the inner ear - a sound-receiving apparatus. The process begins with sound - the oscillatory movement of air or vibration in which sound waves travel towards the listener, eventually reaching the eardrum. At the same time, our ear is extremely sensitive and can sense pressure changes of only 1-10 atmospheres.
Structure of the external ear The external ear consists of the auricle and the external auditory canal. First, sound reaches the ears, which act as receivers of sound waves. The auricle is formed by elastic cartilage, covered on the outside with skin. Determining the direction of sound in a person is associated with binaural hearing, that is, hearing with two ears. Any lateral sound reaches one ear before the other. The difference in time (several fractions of a millisecond) of arrival of sound waves perceived by the left and right ears makes it possible to determine the direction of the sound. In other words, our natural perception of sound is stereophonic.
The human auricle has its own unique relief of convexities, concavities and grooves. This is necessary for the finest acoustic analysis, also allowing you to recognize the direction and source of sound. The folds of the human auricle introduce small frequency distortions into the sound entering the ear canal, depending on the horizontal and vertical localization of the sound source. Thus, the brain receives additional information to clarify the location of the sound source. This effect is sometimes used in acoustics, including to create a sense of surround sound when designing speakers and headphones. The auricle also amplifies sound waves, which then enter the external auditory canal - the space from the concha to the eardrum about 2.5 cm long and about 0.7 cm in diameter. The auditory canal has a weak resonance at a frequency of about 3000 Hz.
Another interesting characteristic of the external auditory canal is the presence of earwax, which is constantly secreted from the glands. Earwax is a waxy secretion of 4000 sebaceous and sulfur glands of the ear canal. Its function is to protect the skin of this passage from bacterial infection and foreign particles or, for example, insects that may get into the ear. U different people the amount of sulfur varies. If there is an excessive accumulation of sulfur, a sulfur plug may form. If the ear canal is completely blocked, there is a feeling of ear congestion and decreased hearing, including the resonance of one’s own voice in the blocked ear. These disorders develop suddenly, most often when water gets into the external auditory canal while swimming.
The outer and middle ears are separated by the eardrum, which is a thin connective tissue plate. The thickness of the eardrum is about 0.1 mm, and the diameter is about 9 millimeters. On the outside it is covered with epithelium, and on the inside with mucous membrane. The eardrum is located obliquely and begins to vibrate when sound waves hit it. The eardrum is extremely sensitive, but once vibration is detected and transmitted, the eardrum returns to its original position in just 0.005 seconds.
The structure of the middle ear In our ear, sound moves to the sensitive cells that perceive sound signals through a matching and amplifying device - the middle ear. The middle ear is a tympanic cavity, which has the shape of a small flat drum with a tightly stretched vibrating membrane and an auditory (Eustachian) tube. In the cavity of the middle ear there are auditory ossicles that articulate with each other - the hammer, incus and stapes. Tiny muscles help transmit sound by regulating the movement of these ossicles. When the sound reaches the eardrum, it vibrates. The handle of the hammer is woven into the eardrum and, by swaying, it sets the hammer in motion. The other end of the malleus is connected to the incus, and the latter is movably articulated with the stapes using a joint. Attached to the stapes is the stapedius muscle, which holds it against the membrane of the oval window (vestibulary window), which separates the middle ear from the inner ear, which is filled with fluid. As a result of the transmission of movement, the stapes, the base of which resembles a piston, is constantly pushed into the membrane of the oval window of the inner ear.
The function of the auditory ossicles is to provide an increase in the pressure of the sound wave when transmitted from the eardrum to the membrane of the oval window. This amplifier (about 30-40 times) helps weak sound waves incident on the eardrum overcome the resistance of the oval window membrane and transmit vibrations to the inner ear. When a sound wave passes from air to liquid, a significant part of the sound energy is lost and, therefore, a sound amplification mechanism is necessary. However, with a loud sound, the same mechanism reduces the sensitivity of the entire system so as not to damage it.
The air pressure inside the middle ear must be the same as the pressure outside the eardrum to ensure normal vibration conditions. To equalize pressure, the tympanic cavity is connected to the nasopharynx using the auditory (Eustachian) tube, 3.5 cm long and about 2 mm in diameter. When swallowing, yawning, and chewing, the Eustachian tube opens to let in outside air. When it changes external pressure sometimes the ears become blocked, which is usually solved by yawning reflexively. Experience shows that ear congestion is solved even more effectively by swallowing movements. Malfunction of the tube leads to pain and even bleeding in the ear.
Structure of the inner ear. The mechanical movements of the bones in the inner ear are converted into electrical signals. The inner ear is a hollow bone formation in the temporal bone, divided into bone canals and cavities containing the receptor apparatus of the auditory analyzer and the organ of balance. Because of its intricate shape, this section of the organ of hearing and balance is called the labyrinth. The bony labyrinth consists of the vestibule, cochlea and semicircular canals, but only the cochlea is directly related to hearing. The cochlea is a canal about 32 mm long, coiled and filled with lymphatic fluids. Having received vibration from the eardrum, the stapes, with its movement, presses on the membrane of the vestibule window and creates pressure fluctuations inside the cochlear fluid. This vibration travels through the fluid of the cochlea and reaches the organ of hearing itself, the spiral or organ of Corti. It turns the vibrations of the liquid into electrical signals that go through the nerves to the brain. In order for the stapes to transmit pressure through the fluid, in the central part of the labyrinth, the vestibule, there is a round window of the cochlea, covered with a flexible membrane. When the piston of the stapes enters the oval window of the vestibule, the membrane of the cochlear window bulges under the pressure of the cochlear fluid. Oscillations in a closed cavity are possible only in the presence of recoil. The role of such return is performed by the membrane of the round window.
The bony labyrinth of the cochlea is wrapped in the shape of a spiral with 2.5 turns and contains inside a membranous labyrinth of the same shape. In some places, the membranous labyrinth is attached to the periosteum of the bony labyrinth by connecting cords. Between the bony and membranous labyrinth there is a fluid - perilymph. The sound wave, amplified by 30-40 dB using the eardrum - auditory ossicles system, reaches the window of the vestibule, and its vibrations are transmitted to the perilymph. The sound wave first passes through the perilymph to the top of the spiral, where through the hole the vibrations propagate to the window of the cochlea. Inside, the membranous labyrinth is filled with another fluid - endolymph. The fluid inside the membranous labyrinth (cochlear duct) is separated from the perilymph above by a flexible covering plate, and below by an elastic main membrane, which together make up the membranous labyrinth. On the main membrane there is a sound-receiving apparatus, the organ of Corti. The main membrane consists of large quantity(24,000) fibrous fibers of various lengths, stretched like strings. These fibers form an elastic network, which as a whole resonates in strictly graded vibrations.
Nerve cells of the organ of Corti convert the oscillatory movements of the plates into electrical signals. They are called hair cells. Inner hair cells are arranged in one row, there are 3.5 thousand of them. Outer hair cells are arranged in three to four rows, there are 12–20 thousand of them. Each hair cell has an elongated shape, it has 60–70 tiny hairs (stereocilia) 4–5 µm long.
All sound energy is concentrated in the space limited by the wall of the bony cochlea and the main membrane (the only pliable place). The fibers of the main membrane have different lengths and, accordingly, different resonant frequencies. The shortest fibers are located near the oval window, their resonant frequency is about 20,000 Hz. The longest ones are at the top of the spiral and have a resonant frequency of about 16 Hz. It turns out that each hair cell, depending on its location on the main membrane, is tuned to a certain sound frequency, and cells tuned to low frequencies, are located in the upper part of the cochlea, and high frequencies are picked up by cells in the lower part of the cochlea. When hair cells die for some reason, a person loses the ability to perceive sounds of the corresponding frequencies.
The sound wave propagates through the perilymph from the window of the vestibule to the window of the cochlea almost instantly, in about 4 * 10-5 seconds. The hydrostatic pressure caused by this wave shifts the covering plate relative to the surface of the organ of Corti. As a result, the integumentary plate deforms the bundles of stereocilia of the hair cells, which leads to their excitation, which is transmitted to the endings of the primary sensory neurons.
Differences in the ionic composition of endolymph and perilymph create a potential difference. And between the endolymph and the intracellular environment of the receptor cells, the potential difference reaches approximately 0.16 volts. Such a significant potential difference contributes to the excitation of hair cells even under the influence of weak sound signals, causing slight vibrations of the main membrane. When the stereocilia of hair cells are deformed, a receptor potential arises in them, which leads to the release of a regulator that acts on the endings of the auditory nerve fibers and thereby excites them.
Hair cells are connected to the endings of nerve fibers that, upon exiting the organ of Corti, form the auditory nerve (cochlear branch of the vestibulocochlear nerve). Sound waves converted into electrical impulses are transmitted along the auditory nerve to temporal zone cerebral cortex.
The auditory nerve consists of thousands of tiny nerve fibers. Each of them starts from a certain part of the cochlea and, thereby, transmits a certain sound frequency. Each fiber of the auditory nerve is associated with several hair cells, so that the central nervous system about 10,000 fibers arrive. Impulses from low-frequency sounds are transmitted through fibers emanating from the top of the cochlea, and from high-frequency sounds - through fibers connected to its base. Thus, the function of the inner ear is to convert mechanical vibrations into electrical ones, since the brain can only perceive electrical signals.
The organ of hearing is the apparatus through which we receive sound information. But we hear the way our brain perceives, processes and remembers. Sound ideas or images are created in the brain. And, if music sounds in our head or someone’s voice is remembered, then due to the fact that the brain has input filters, a storage device and a sound card, it can be both a boring speaker and a convenient music center for us.
Analyzers– a set of nervous formations that provide awareness and assessment of stimuli acting on the body. The analyzer consists of receptors that perceive irritation, a conductive part and a central part - a certain area of \u200b\u200bthe cerebral cortex where sensations are formed.
Receptors– sensitive endings that perceive irritation and convert external signals into nerve impulses. Conductor part The analyzer consists of the corresponding nerve and pathways. The central part of the analyzer is one of the sections of the central nervous system.
Visual analyzerprovides visual information from the environment and consists of
of three parts: peripheral - the eyes, conductive - the optic nerve and central - the subcortical and visual zones of the cerebral cortex.
Eye comprises eyeball and auxiliary apparatus, which includes the eyelids, eyelashes, lacrimal glands and muscles of the eyeball.
Eyeball located in the orbit and has a spherical shape and 3 shells: fibrous, the posterior part of which is formed by an opaque protein shell ( sclera),vascular And mesh. The part of the choroid supplied with pigments is called iris. At the center of the iris is pupil, which can change the diameter of its opening due to contraction of the eye muscles. Rear end retina perceives light irritation. Its front part is blind and does not contain photosensitive elements. The photosensitive elements of the retina are sticks(provide vision in twilight and darkness) and cones(color vision receptors that work in high light). Cones are located closer to the center of the retina (macula macula), and rods are concentrated at its periphery. The exit point of the optic nerve is called blind spot.
The eyeball cavity is filled vitreous. The lens has the shape of a biconvex lens. It is able to change its curvature when the ciliary muscle contracts. When viewing close objects, the lens contracts, and when viewing distant objects, it expands. This ability of the lens is called accommodation. Between the cornea and the iris is the anterior chamber of the eye, and between the iris and the lens is the posterior chamber. Both chambers are filled with a clear liquid. Rays of light, reflected from objects, pass through the cornea, moist chambers, lens, vitreous body and, thanks to refraction in the lens, fall on yellow spot The retina is the place of best vision. In this case, there arises real, inverse, reduced image of an object. From the retina, along the optic nerve, impulses enter the central part of the analyzer - the visual zone of the cerebral cortex, located in the occipital lobe. In the cortex, information received from retinal receptors is processed and a person perceives the natural reflection of an object.
Normal visual perception is due to:
– sufficient luminous flux;
– focusing the image on the retina (focusing in front of the retina means myopia, and behind the retina means farsightedness);
– implementation of the accommodative reflex.
The most important indicator of vision is its acuity, i.e. the ultimate ability of the eye to distinguish small objects.
Organ of hearing and balance.
Hearing analyzer ensures the perception of sound information and its processing in the central parts of the cerebral cortex. The peripheral part of the analyzer is formed by the inner ear and the auditory nerve. The central part is formed by the subcortical centers of the midbrain and diencephalon and the temporal zone of the cortex.
Ear– a paired organ consisting of the outer, middle and inner ears
Outer ear includes the auricle, external auditory canal and eardrum.
Middle ear consists of the tympanic cavity, a chain of auditory ossicles and an auditory (Eustachian) tube. The auditory tube connects the tympanic cavity with the nasopharynx cavity. This ensures equalization of pressure on both sides of the eardrum. The auditory ossicles - the hammer, incus and stapes - connect the eardrum with the membrane of the oval window leading to the cochlea. The middle ear transmits sound waves from a low-density environment (air) to a high-density environment (endolymph), which contains the receptor cells of the inner ear. Inner ear located in the thickness of the temporal bone and consists of a bony labyrinth and a membranous labyrinth located in it. The space between them is filled with perilymph, and the cavity of the membranous labyrinth is filled with endolymph. The bony labyrinth is divided into three sections: vestibule, cochlea and semicircular canals. The organ of hearing includes the cochlea - a spiral canal of 2.5 turns. The cochlear cavity is divided by a membranous main membrane consisting of fibers of different lengths. On the main membrane there are receptor hair cells. Vibrations of the eardrum are transmitted to the auditory ossicles. They amplify these vibrations almost 50 times and through oval window are transmitted to the cochlear fluid, where they are perceived by the fibers of the main membrane. The receptor cells of the cochlea perceive irritation coming from the fibers and transmit it along the auditory nerve to the temporal zone of the cerebral cortex. The human ear perceives sounds with a frequency from 16 to 20,000 Hz.
Organ of balance, or vestibular apparatus ,
formed by two bags, filled with liquid, and three semicircular canals. Receptor hair cells located on the bottom and inside of the bags. Adjacent to them is a membrane with crystals - otoliths containing calcium ions. The semicircular canals are located in three mutually perpendicular planes. At the base of the canals are hair cells. Receptors of the otolithic apparatus respond to acceleration or deceleration of rectilinear movement. The semicircular canal receptors are stimulated by changes in rotational movements. Impulses from the vestibular apparatus travel through the vestibular nerve to the central nervous system. Impulses from receptors in muscles, tendons, and soles also come here. Functionally, the vestibular apparatus is connected with the cerebellum, which is responsible for coordination of movements and orientation of a person in space.
Taste analyzer
consists of receptors located in the taste buds of the tongue, a nerve that conducts impulses to the central section of the analyzer, which is located on the inner surfaces of the temporal and frontal lobes.
Olfactory analyzer
represented by olfactory receptors located in the nasal mucosa. Along the olfactory nerve, the signal from the receptors enters the olfactory zone of the cerebral cortex, located next to the taste zone.
Skin analyzer consists of receptors that perceive pressure, pain, temperature, touch, pathways and zones skin sensitivity located in the posterior central gyrus.
Introduction
Conclusion
Bibliography
Introduction
The society in which we live is Information society, where the main factor of production is knowledge, the main product of production is services, and the characteristic features of society are computerization, as well as a sharp increase in creativity in work. The role of connections with other countries is increasing, and the process of globalization is taking place in all spheres of society.
A key role in communication between states is played by professions related to foreign languages, linguistics, social sciences. There is an increasing need to study speech recognition systems for automated translation, which will help increase labor productivity in areas of the economy related to intercultural communication. Therefore, it is important to study the physiology and mechanisms of functioning of the auditory analyzer as a means of perceiving and transmitting speech to the corresponding part of the brain for subsequent processing and synthesis of new speech units.
The auditory analyzer is a set of mechanical, receptor and nervous structures, the activity of which ensures the perception of sound vibrations by humans and animals. From an anatomical point of view auditory system can be divided into the outer, middle and inner ear, auditory nerve and central auditory pathways. From the point of view of the processes that ultimately lead to the perception of hearing, the auditory system is divided into sound-conducting and sound-perceiving.
IN different conditions environment, under the influence of many factors, the sensitivity of the hearing analyzer may change. To study these factors there are various methods hearing research.
auditory analyzer physiology sensitivity
1. The importance of studying human analyzers from the point of view of modern information technologies
Already several decades ago, people made attempts to create speech synthesis and recognition systems in modern information technologies. Of course, all these attempts began with the study of the anatomy and principles of operation of the human speech and auditory organs, in the hope of simulating them using a computer and special electronic devices.
What are the features of the human auditory analyzer? The auditory analyzer captures the shape of the sound wave, the frequency spectrum of pure tones and noises, carries out, within certain limits, the analysis and synthesis of the frequency components of sound stimuli, detects and identifies sounds in a wide range of intensities and frequencies. The auditory analyzer allows you to differentiate sound stimuli and determine the direction of the sound, as well as the distance of its source. The ears sense vibrations in the air and convert them into electrical signals that travel to the brain. As a result of processing by the human brain, these signals turn into images. Creation of such information processing algorithms for computer technology and there is a scientific problem, the solution of which is necessary to develop the most error-free speech recognition systems.
Many users dictate the text of documents using speech recognition programs. This opportunity is relevant, for example, for doctors conducting an examination (during which their hands are usually busy) and at the same time recording its results. PC users can use speech recognition programs to enter commands, meaning the spoken word will be perceived by the system as a mouse click. The user commands: “Open file”, “Send mail” or “New window”, and the computer performs the corresponding actions. This is especially true for people with disabilities - instead of a mouse and keyboard, they will be able to control the computer using their voice.
Studying the inner ear helps researchers understand the mechanisms by which humans are able to recognize speech, although it is not that simple. Man “spies” on many inventions from nature, and such attempts are also made by specialists in the field of speech synthesis and recognition.
2. Types of human analyzers and their a brief description of
Analyzers (from the Greek analysis - decomposition, dismemberment) are a system of sensitive nervous formations that analyze and synthesize phenomena in the external and internal environment of the body. The term was introduced into the neurological literature by I.P. Pavlov, according to whose ideas each analyzer consists of specific perceptive formations (receptors, sensory organs) that make up the peripheral part of the analyzer, the corresponding nerves connecting these receptors with different floors of the central nervous system (conductive part), and the brain end, which is represented in higher animals in the cortex of the large cerebral hemispheres.
Depending on the receptor function, analyzers of the external and internal environment are distinguished. The first receptors are directed towards external environment and are adapted to analyze phenomena occurring in the surrounding world. Such analyzers include visual analyzer, hearing analyzer, skin, olfactory, gustatory. Analyzers of the internal environment are afferent nervous devices, the receptor apparatus of which is located in internal organs and are adapted to analyze what is happening in the body itself. Such analyzers also include a motor analyzer (its receptor apparatus is represented by muscle spindles and Golgi receptors), which provides the possibility of precise control of the musculoskeletal system. Another internal analyzer, the vestibular one, closely interacts with the movement analyzer, also plays a significant role in the mechanisms of statokinetic coordination. The human motor analyzer also includes a special section that ensures the transmission of signals from the receptors of the speech organs to the higher levels of the central nervous system. Due to the importance of this section in the activity of the human brain, it is sometimes considered a “speech-motor analyzer.”
The receptor apparatus of each analyzer is adapted to transform a certain type of energy into nervous excitation. Thus, sound receptors selectively react to sound stimulation, light - to light, taste - to chemical, skin - to tactile-temperature, etc. The specialization of receptors ensures the analysis of external world phenomena into their individual elements already at the level of the peripheral part of the analyzer.
Biological role analyzers is that they are specialized tracking systems that inform the body about all events occurring in environment and inside it. From the huge flow of signals continuously entering the brain through external and internal analyzers, that useful information is selected that turns out to be essential in the processes of self-regulation (maintaining an optimal, constant level of functioning of the body) and active behavior of animals in the environment. Experiments show that the complex analytical and synthetic activity of the brain, determined by factors of the external and internal environment, is carried out according to the polyanalyzer principle. This means that the entire complex neurodynamics of cortical processes, which forms the integral activity of the brain, consists of a complex interaction of analyzers. But this concerns a different topic. Let's move directly to the auditory analyzer and look at it in more detail.
3. Auditory analyzer as a means of human perception of sound information
3.1 Physiology of the auditory analyzer
The peripheral section of the auditory analyzer (the auditory analyzer with the organ of balance - the ear (auris)) is a very complex sensory organ. The endings of its nerve are located deep in the ear, due to which they are protected from the action of all kinds of extraneous irritants, but at the same time are easily accessible to sound stimulation. The organ of hearing contains three types of receptors:
a) receptors that perceive sound vibrations (vibrations of air waves), which we perceive as sound;
b) receptors that enable us to determine the position of our body in space;
c) receptors that perceive changes in the direction and speed of movement.
The ear is usually divided into three sections: the outer, middle and inner ear.
Outer earconsists of the auricle and the external auditory canal. The auricle is built of elastic elastic cartilage, covered with a thin, inactive layer of skin. She is a collector of sound waves; in humans it is motionless and does not play an important role, unlike animals; even with her complete absence There is no noticeable hearing impairment.
The external auditory canal is a slightly curved canal about 2.5 cm in length. This canal is lined with skin with small hairs and contains special glands, similar to large apocrine glands of the skin, secreting earwax, which, together with the hairs, protects the outer ear from clogging with dust. It consists of an outer section, the cartilaginous external auditory canal, and an internal section, the bony auditory canal, located in the temporal bone. Its inner end is closed by a thin elastic eardrum, which is a continuation of the skin of the external auditory canal and separates it from the cavity of the middle ear. The outer ear plays only a supporting role in the organ of hearing, participating in the collection and conduction of sounds.
Middle ear, or tympanic cavity (Fig. 1), is located inside the temporal bone between the external auditory canal, from which it is separated by the tympanic membrane, and the inner ear; it is a very small, irregularly shaped cavity with a capacity of up to 0.75 ml, which communicates with the accessory cavities - the cells of the mastoid process and the pharyngeal cavity (see below).
Rice. 1. Sectional view of the hearing organ. 1 - geniculate ganglion of the facial nerve; 2 - facial nerve; 3 - hammer; 4 - superior semicircular canal; 5 - posterior semicircular canal; 6 - anvil; 7 - bony part of the external auditory canal; 8 - cartilaginous part of the external auditory canal; 9 - eardrum; 10 - bone part auditory tube; 11 - cartilaginous part of the auditory tube; 12 - greater superficial petrosal nerve; 13 - top of the pyramid.
On the medial wall of the tympanic cavity, facing the inner ear, there are two openings: the oval window of the vestibule and the round window of the cochlea; the first is covered by the stirrup plate. The tympanic cavity communicates with the auditory (Eustachian) tube (tuba auditiva) through a small (4 cm long) upper section pharynx - nasopharynx. The opening of the pipe opens on the side wall of the pharynx and in this way communicates with the outside air. Every time the auditory tube opens (which happens with every swallowing movement), the air in the tympanic cavity is renewed. Thanks to it, the pressure on the eardrum from the side of the tympanic cavity is always maintained at the level of outside air pressure, and thus, the outside and inside of the eardrum is exposed to the same atmospheric pressure.
This balancing of pressure on both sides of the eardrum is very important, since normal fluctuations are possible only when the pressure of the outside air is equal to the pressure in the cavity of the middle ear. When there is a difference between atmospheric air pressure and the pressure of the tympanic cavity, hearing acuity is impaired. Thus, the auditory tube is a kind of safety valve that equalizes the pressure in the middle ear.
The walls of the tympanic cavity and especially the auditory tube are lined with epithelium, and the mucous tubes are lined with ciliated epithelium; the vibration of its hairs is directed towards the pharynx.
The pharyngeal end of the auditory tube is rich in mucous glands and lymph nodes.
On the lateral side of the cavity is the eardrum. The eardrum (membrana tympani) (Fig. 2) perceives sound vibrations in the air and transmits them to the sound conducting system of the middle ear. It has the shape of a circle or ellipse with a diameter of 9 and 11 mm and consists of an elastic connective tissue, the fibers of which are arranged radially on the outer surface, and circularly on the inner surface; its thickness is only 0.1 mm; it is stretched somewhat obliquely: from top to bottom and from back to front, it is slightly concave inward, since the mentioned muscle stretches from the walls of the tympanic cavity to the handle of the malleus, stretching the eardrum (it pulls the membrane inward). The chain of auditory ossicles serves to transmit air vibrations from the eardrum to the fluid filling the inner ear. The eardrum is not very stretched and does not produce its own tone, but transmits only the sound waves it receives. Due to the fact that vibrations of the eardrum decay very quickly, it is an excellent transmitter of pressure and almost does not distort the shape of the sound wave. On the outside, the eardrum is covered with thinned skin, and on the surface facing the tympanic cavity - with a mucous membrane lined with a flat stratified epithelium.
Between the eardrum and the oval window there is a system of small auditory ossicles that transmit vibrations of the eardrum to the inner ear: the malleus, incus and stapes, connected by joints and ligaments that are driven by two small muscles. The hammer is incremented to inner surface the eardrum with its handle, and the head is articulated with the anvil. The anvil, with one of its processes, is connected to the stirrup, which is located horizontally and with its wide base (plate) inserted into the oval window, tightly adjacent to its membrane.
Rice. 2. Eardrum and auditory ossicles from the inside. 1 - head of the hammer; 2 - its upper ligament; 3 - cave of the tympanic cavity; 4 - anvil; 5 - a bunch of it; 6 - drum string; 7 - pyramidal elevation; 8 - stirrup; 9 - hammer handle; 10 - eardrum; 11 - Eustachian tube; 12 - partition between the half-channels for the pipe and for the muscle; 13 - muscle that strains the tympanic membrane; 14 - anterior process of the malleus
The muscles of the tympanic cavity deserve a lot of attention. One of them is m. tensor tympani - attached to the neck of the malleus. When it contracts, the articulation between the malleus and the incus is fixed and the tension of the eardrum increases, which occurs with strong sound vibrations. At the same time, the base of the stapes is slightly pressed into the oval window.
The second muscle is m. stapedius (the smallest striated muscle in the human body) - attaches to the head of the stapes. When this muscle contracts, the articulation between the incus and the stapes is pulled downward and limits the movement of the stapes in the oval window.
Inner ear.The inner ear is the most important and most complex arranged part hearing aid, called the labyrinth. The labyrinth of the inner ear is located deep in the pyramid of the temporal bone, as if in a bone case between the middle ear and the internal auditory canal. The size of the bony ear labyrinth along its long axis does not exceed 2 cm. It is separated from the middle ear by the oval and round windows. The opening of the internal auditory canal on the surface of the pyramid of the temporal bone, through which the auditory nerve exits the labyrinth, is closed by a thin bone plate with small holes for the auditory nerve fibers to exit the inner ear. Inside the bone labyrinth there is a closed connective tissue membranous labyrinth, which exactly repeats the shape of the bone labyrinth, but is somewhat smaller in size. The narrow space between the bony and membranous labyrinths is filled with a fluid similar in composition to lymph and called perilimph. All internal cavity The membranous labyrinth is also filled with a fluid called endolymph. The membranous labyrinth is connected in many places to the walls of the bony labyrinth by dense cords running through the perilymphatic space. Thanks to this arrangement, the membranous labyrinth is suspended inside the bony labyrinth, just as the brain is suspended (inside the skull on its meninges.
The labyrinth (Fig. 3 and 4) consists of three sections: the vestibule of the labyrinth, the semicircular canals and the cochlea.
Rice. 3. Diagram of the relationship of the membranous labyrinth to the bony labyrinth. 1 - duct connecting the utricle with the sac; 2 - superior membranous ampulla; 3 - endolymphatic duct; 4 - endolymphatic sac; 5 - translymphatic space; 6 - pyramid of the temporal bone: 7 - apex of the membranous cochlear duct; 8 - communication between both staircases (helicotrema); 9 - cochlear membranous passage; 10 - staircase vestibule; 11 - drum ladder; 12 - bag; 13 - connecting stroke; 14 - perilymphatic duct; 15 - round window of the cochlea; 16 - oval window of the vestibule; 17 - tympanic cavity; 18 - blind end of the cochlear duct; 19 - posterior membranous ampulla; 20 - utricle; 21 - semicircular canal; 22 - upper semicircular course
Rice. 4. Transverse section through the cochlea. 1 - staircase vestibule; 2 - Reissner's membrane; 3 - integumentary membrane; 4 - cochlear canal, in which the organ of Corti is located (between the integumentary and main membranes); 5 and 16 - auditory cells with cilia; 6 - supporting cells; 7 - spiral ligament; 8 and 14 - bone snails; 9 - supporting cell; 10 and 15 - special supporting cells (the so-called Corti cells - pillars); 11 - scala tympani; 12 - main membrane; 13 - nerve cells of the spiral cochlear ganglion
The membranous vestibule (vestibulum) is a small oval cavity occupying middle part labyrinth and consisting of two vesicles-sacs connected to each other by a narrow tubule; one of them, the posterior one, the so-called utricle (utriculus), communicates with the membranous semicircular canals by five openings, and the anterior sac (sacculus) communicates with the membranous cochlea. Each of the sacs of the vestibule apparatus is filled with endolymph. The walls of the sacs are lined flat epithelium, with the exception of one area - the so-called spot (macula), where there is a cylindrical epithelium containing supporting and hair cells bearing thin processes on their surface facing the cavity of the sac. Higher animals have small lime crystals (otoliths), glued into one lump together with the hairs of neuroepithelial cells, in which the nerve fibers of the vestibular nerve (ramus vestibularis - branch of the auditory nerve) end.
Behind the vestibule there are three mutually perpendicular semicircular canals (canales semicirculares) - one in the horizontal plane and two in the vertical. The semicircular canals are very narrow tubes filled with endolymph. Each of the canals forms an extension at one of its ends - an ampulla, where the endings of the vestibular nerve are located, distributed in the cells of the sensitive epithelium, concentrated in the so-called auditory crest (crista acustica). The cells of the sensitive epithelium of the auditory comb are very similar to those present in the speck - on the surface facing the cavity of the ampulla, they bear hairs that are glued together and form a kind of brush (cupula). The free surface of the brush reaches the opposite (upper) wall of the canal, leaving an insignificant lumen of its cavity free, preventing the movement of endolymph.
In front of the vestibule is the cochlea, which is a membranous, spirally convoluted canal, also located inside the bone. The cochlear spiral in humans makes 2 3/4revolution around the central bone axis and ends blind. The bony axis of the cochlea with its apex faces the middle ear, and its base closes the internal auditory canal.
Into the cavity of the spiral canal of the cochlea along its entire length, a spiral bone plate also extends and protrudes from the bony axis - a septum that divides the spiral cavity of the cochlea into two passages: the upper one, communicating with the vestibule of the labyrinth, the so-called staircase of the vestibule (scala vestibuli), and the lower one, abutting one end into the membrane of the round window of the tympanic cavity and therefore called the scala tympani (scala tympani). These passages are called staircases because, curling in a spiral, they resemble a staircase with an obliquely rising strip, but without steps. At the end of the cochlea, both passages are connected by a hole about 0.03 mm in diameter.
This longitudinal bone plate blocking the cavity of the cochlea, extending from the concave wall, does not reach the opposite side, and its continuation is a connective tissue membranous spiral plate, called the main membrane, or the main membrane (membrana basilaris), which is already closely adjacent to the convex opposite wall along the the entire length of the common cavity of the cochlea.
Another membrane (Reisner’s) extends from the edge of the bone plate at an angle above the main one, which limits a small middle passage between the first two passages (scales). This passage is called the cochlear canal (ductus cochlearis) and communicates with the vestibule sac; it is the organ of hearing in the proper sense of the word. The canal of the cochlea in a cross section has the shape of a triangle and, in turn, is divided (but not completely) into two floors by a third membrane - the integumentary membrane (membrana tectoria), which apparently plays a large role in the process of perception of sensations. In the lower floor of this last canal, on the main membrane in the form of a protrusion of the neuroepithelium, there is a very complex device, the actual perceptive apparatus of the auditory analyzer - the spiral (organon spirale Cortii) (Fig. 5), washed together with the main membrane by the intralabyrinthine fluid and playing in relation to to hearing the same role as the retina in relation to vision.
Rice. 5. Microscopic structure of the organ of Corti. 1 - main membrane; 2 - cover membrane; 3 - auditory cells; 4 - auditory ganglion cells
The spiral organ consists of numerous diverse supporting and epithelial cells located on the main membrane. The elongated cells are arranged in two rows and are called pillars of Corti. The cells of both rows are slightly inclined towards each other and form up to 4000 arcs of Corti throughout the cochlea. In this case, a so-called internal tunnel is formed in the cochlear canal, filled with intercellular substance. On the inner surface of the Corti columns there is a number of cylindrical epithelial cells, on the free surface of which there are 15-20 hairs - these are sensitive, perceptive, so-called hair cells. Thin and long fibers - auditory hairs, sticking together, form delicate brushes on each such cell. Adjacent to the outer side of these auditory cells are the supporting Deiters cells. Thus, the hair cells are anchored to the main membrane. Thin nerve fibers without pulp approach them and form an extremely delicate fibrillar network in them. The auditory nerve (its branch - ramus cochlearis) penetrates the middle of the cochlea and runs along its axis, giving off numerous branches. Here, each pulpy nerve fiber loses its myelin and becomes a nerve cell, which, like the cells of the spiral ganglia, has a connective tissue sheath and glial meningeal cells. The whole amount of these nerve cells as a whole and forms a spiral ganglion (ganglion spirale), occupying the entire periphery of the cochlear axis. From this nerve ganglion, nerve fibers are already sent to the perceptive apparatus - the spiral organ.
The main membrane itself, on which the spiral organ is located, consists of the thinnest, dense and tightly stretched fibers (“strings”) (about 30,000), which, starting from the base of the cochlea (near the oval window), gradually lengthen to its upper curl, ranging from 50 to 500 ?(more precisely, from 0.04125 to 0.495 mm), i.e. short near the oval window, they become increasingly longer towards the apex of the cochlea, increasing by about 10-12 times. The length of the main membrane from the base to the apex of the cochlea is approximately 33.5 mm.
Helmholtz, who created the theory of hearing at the end of the last century, compared the main membrane of the cochlea with its fibers of different lengths with musical instrument- a harp, only in this living harp a huge number of “strings” are stretched.
The perceiving apparatus of auditory stimuli is the spiral (Corti) organ of the cochlea. The vestibule and semicircular canals play the role of balance organs. True, the perception of the position and movement of the body in space depends on the joint function of many senses: vision, touch, muscle sense, etc., i.e. reflex activity necessary to maintain balance is provided by impulses in various organs. But the main role in this belongs to the vestibule and semicircular canals.
3.2 Sensitivity of the hearing analyzer
The human ear perceives air vibrations from 16 to 20,000 Hz as sound. The upper limit of perceived sounds depends on age: the older the person, the lower it is; Often older people cannot hear high tones, such as the sound made by a cricket. In many animals upper limit lies above; In dogs, for example, it is possible to form a whole series of conditioned reflexes to sounds inaudible to humans.
With fluctuations up to 300 Hz and above 3000 Hz, the sensitivity decreases sharply: for example, at 20 Hz, as well as at 20,000 Hz. With age, the sensitivity of the auditory analyzer, as a rule, decreases significantly, but mainly to high-frequency sounds, while to low-frequency sounds (up to 1000 vibrations per second) it remains almost unchanged until old age.
This means that to improve the quality of speech recognition, computer systems can exclude from analysis frequencies that lie outside the range of 300-3000 Hz or even outside the range of 300-2400 Hz.
In conditions of complete silence, hearing sensitivity increases. If the tone begins to sound certain height and constant intensity, then, due to adaptation to it, the sensation of loudness decreases, first quickly, and then more and more slowly. However, although to a lesser extent, sensitivity to sounds that are more or less close in vibration frequency to the sounding tone decreases. However, adaptation usually does not extend to the entire range of perceived sounds. After the sound stops, due to adaptation to silence, the previous level of sensitivity is restored within 10-15 seconds.
Adaptation partly depends on the peripheral part of the analyzer, namely on changes in both the amplifying function of the sound apparatus and the excitability of the hair cells of the organ of Corti. Central department The analyzer also takes part in adaptation phenomena, as evidenced by the fact that when sound is applied to only one ear, shifts in sensitivity are observed in both ears.
Sensitivity also changes with the simultaneous action of two tones of different heights. In the latter case, a weak sound is drowned out by a stronger one, mainly because the focus of excitation, which arises in the cortex under the influence of a strong sound, reduces, due to negative induction, the excitability of other parts of the cortical section of the same analyzer.
Prolonged exposure to strong sounds can cause prohibitive inhibition of cortical cells. As a result, the sensitivity of the auditory analyzer sharply decreases. This condition persists for some time after the irritation has stopped.
Conclusion
The complex structure of the auditory analyzer system is due to a multi-stage signal transmission algorithm temporal region brain The outer and middle ears transmit sound vibrations to the cochlea, located in the inner ear. Sensitive hairs located in the cochlea convert vibrations into electrical signals that travel along nerves to the auditory area of the brain.
When considering the functioning of an auditory analyzer for further application of knowledge when creating speech recognition programs, one should also take into account the sensitivity limits of the hearing organ. The frequency range of sound vibrations perceived by humans is 16-20,000 Hz. However, the frequency range of speech is already 300-4000 Hz. Speech remains intelligible when the frequency range is further narrowed to 300-2400 Hz. This fact can be used in speech recognition systems to reduce the influence of interference.
Bibliography
1.P.A. Baranov, A.V. Vorontsov, S.V. Shevchenko. Social science: complete guide. Moscow 2013
2.Big Soviet Encyclopedia, 3rd edition (1969-1978), volume 23.
.A.V. Frolov, G.V. Frolov. Speech synthesis and recognition. Modern solutions.
.Dushkov B.A., Korolev A.V., Smirnov B.A. encyclopedic Dictionary: Labor psychology, management, engineering psychology and ergonomics. Moscow, 2005
.Kucherov A.G. Anatomy, physiology and methods of studying the organ of hearing and balance. Moscow, 2002
.Stankov A.G. Human anatomy. Moscow, 1959
7.http://ioi-911. ucoz.ru/publ/1-1-0-47
.
Tutoring
Need help studying a topic?
Our specialists will advise or provide tutoring services on topics that interest you.
Submit your application indicating the topic right now to find out about the possibility of obtaining a consultation.
Loading...