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Encyclopedia > Auditory system

The auditory system is the sensory system for the sense of hearing. The human eye is the first element of a sensory system: in this case, vision, for the visual system. ... Hearing (or audition) is one of the traditional five senses, and refers to the ability to detect sound. ...

Contents

Ear

Anatomy of the human ear. (The length of the auditory canal is exaggerated in this image)
Anatomy of the human ear. (The length of the auditory canal is exaggerated in this image)
Main article: Ear

... ... For other uses, see Ear (disambiguation). ...

Outer ear

Main article: Outer ear

The folds of cartilage surrounding the ear canal are called the pinna. Sound waves are reflected and attenuated when they hit the pinna, and these changes provide additional information that will help the brain determine the direction from which the sounds came. The outer ear is the external portion of the ear. ...


The sound waves enter the auditory canal, a deceptively simple tube. The ear canal amplifies sounds that are between 3 and 12 kHz. At the far end of the ear canal is the eardrum (or tympanic membrane), which marks the beginning of the middle ear. Anatomy of the human ear. ... A kilohertz (kHz) is a unit of frequency equal to 1,000 hertz (1,000 cycles per second). ... The tympanic membrane, colloquially known as the eardrum, is a thin membrane that separates the external ear from the middle ear. ... The middle ear is the portion of the ear internal to the eardrum, and external to the oval window of the cochlea. ...


Middle ear

Main article: Middle ear

Sound waves traveling through the ear canal will hit the tympanum, or eardrum. This wave information travels across the air-filled middle ear cavity via a series of delicate bones: the malleus (hammer), incus (anvil) and stapes (stirrup). These ossicles act as a lever and a teletype, converting the lower-pressure eardrum sound vibrations into higher-pressure sound vibrations at another, smaller membrane called the oval (or elliptical) window. Higher pressure is necessary because the inner ear beyond the oval window contains liquid rather than air. The sound is not amplified uniformly across the ossicular chain. The auditory reflex of the middle ear muscles helps protect the inner ear from damage. The middle ear still contains the sound information in wave form; it is converted to nerve impulses in the cochlea. The middle ear is the portion of the ear internal to the eardrum, and external to the oval window of the cochlea. ... The tympanic membrane, colloquially known as the eardrum, is a thin membrane that separates the external ear from the middle ear. ... The malleus is hammer-shaped small bone or ossicle of the middle ear which connects with the incus and is attached to the inner surface of the eardrum. ... This article refers to a bone in the mammalian ear. ... The stapes or stirrup is the stirrup-shaped small bone or ossicle in the middle ear which attaches the incus to the fenestra ovalis, the oval window which is adjacent to the vestibule of the inner ear. ... The ossicles (also called auditory ossicles) are the three smallest bones in the human body. ...


Inner ear

Cochlea
Diagrammatic longitudinal section of the cochlea. Scala media is labeled as ductus cochlearis at right.
Main article: Inner ear

The inner ear consists of the cochlea and several non-auditory structures. The cochlea has three fluid-filled sections, and supports a fluid wave driven by pressure across the basilar membrane separating two of the sections. Strikingly, one section, called the cochlear duct or scala media, contains an extracellular fluid similar in composition to endolymph, which is usually found inside of cells. The organ of Corti is located at this duct, and transforms mechanical waves to electric signals in neurons. Image File history File links Gray928. ... Scala media is a endolymph filled cavity inside the cochlea, located in between the scala tympani and the scala vestibuli, separated by the basilar membrane and Reissners membrane(the vestibular membrane) respectively. ... Inner ear The inner ear is the bony labyrinth, a system of passages comprising two main functional parts: the organ of hearing, or cochlea and the vestibular apparatus, the organ of balance that consists of three semicircular canals and the vestibule. ... The cochlea is the auditory portion of the inner ear. ... Cross section of the cochlea. ... Scala media is a endolymph filled cavity inside the cochlea, located in between the scala tympani and the scala vestibuli, separated by the basilar membrane and Reissners membrane(the vestibular membrane) respectively. ... Endolymph is the fluid contained in the membranous labyrinth of the inner ear. ...


Organ of Corti

Main article: Organ of Corti

The organ of Corti forms a ribbon of sensory epithelium which runs lengthwise down the entire cochlea. The hair cells of the organ of Corti transform the fluid waves into nerve signals. The journey of a billion nerves begins with this first step; from here further processing leads to a panoply of auditory reactions and sensations. The organ of Corti is the organ in the inner ear of mammals that contains auditory sensory cells, or hair cells. // Structure and function It has highly specialized structures that respond to fluid-borne vibrations in the cochlea with a shearing vector in the hairs of some cochlear hair cells. ...

The organ of Corti located at the scala media.
The organ of Corti located at the scala media.

made in inkscape File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... made in inkscape File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... The organ of Corti is the organ in the inner ear of mammals that contains auditory sensory cells, or hair cells. // Structure and function It has highly specialized structures that respond to fluid-borne vibrations in the cochlea with a shearing vector in the hairs of some cochlear hair cells. ... Scala media is a endolymph filled cavity inside the cochlea, located in between the scala tympani and the scala vestibuli, separated by the basilar membrane and Reissners membrane(the vestibular membrane) respectively. ...

Hair cell

Main article: Hair cell

Hair cells are columnar cells, each with a bundle of 100-200 specialized cilia at the top, for which they are named. These cilia are the mechanosensors for hearing. Lightly resting atop the longest cilia is the tectorial membrane, which moves back and forth with each cycle of sound, tilting the cilia and allowing electric current into the hair cell. Hair cells are the sensory cells of both the auditory system and the vestibular system in all vertebrates. ... cross-section of two cilia, showing 9+2 structure A cilium (plural cilia) is a fine projection from a eukaryotic cell that constantly beats in one direction. ...


Hair cells, like the photoreceptors of the eye, show a graded response, instead of the spikes typical of other neurons. These graded potentials are not bound by the “all or none” properties of an action potential. A. A schematic view of an idealized action potential illustrates its various phases as the action potential passes a point on a cell membrane. ...


At this point, one may ask how such a wiggle of a hair bundle triggers a difference in membrane potential. The current model is that cilia are attached to one another by “tip links”, structures which link the tips of one cilium to another. Stretching and compressing the tip links may open an ion channel and produce the receptor potential in the hair cell. Recently it has been shown that cdh23 and pchh15 are the adhesion molecules associated with these tip links. It is thought that a calcium driven motor causes a shortening of these links to regenerate tensions. This regeneration of tension allows for apprehension of prolonged auditory stimulation.


Neurons

Main article: Hair cell neural connection

Afferent neurons innervate cochlear inner hair cells, at synapses where the neurotransmitter glutamate communicates signals from the hair cells to the dendrites of the primary auditory neurons. Hair cells are the sensory cells of both the auditory system and the vestibular system in all vertebrates. ... Glutamate is the anion of glutamic acid. ...


There are far fewer inner hair cells in the cochlea than afferent nerve fibers. The neural dendrites belong to neurons of the auditory nerve, which in turn joins the vestibular nerve to form the vestibulocochlear nerve, or cranial nerve number VIII.[1] The auditory nerve is the nerve along which the sensory cells (the hair cells) of the inner ear transmit information to the brain. ... The vestibular nerve is one of the two branches of the Vestibulocochlear nerve (the cochlear nerve is the other. ... The vestibulocochlear nerve (also known as the auditory or acoustic nerve) is the eighth of twelve cranial nerves, and is responsible for transmitting sound and equilibrium (balance) information from the inner ear to the brain. ...


Efferent projections from the brain to the cochlea also play a role in the perception of sound. Efferent synapses occur on outer hair cells and on afferent (towards the brain) dendrites under inner hair cells.


Central auditory system

This sound information, now re-encoded, travels down the vestibulocochlear nerve, through parts of the brainstem (for example, the cochlear nucleus and inferior colliculus), further processed at each waypoint. The information eventually reaches the thalamus, and from there it is relayed to the cortex. In the human brain, the primary auditory cortex is located in the temporal lobe. The vestibulocochlear nerve (also known as the auditory or acoustic nerve) is the eighth of twelve cranial nerves, and is responsible for transmitting sound and equilibrium (balance) information from the inner ear to the brain. ... The brain stem is the stalk of the brain below the cerebral hemispheres. ... The cochlear nuclei consist of: (a) the lateral cochlear nucleus, corresponding to the tuberculum acusticum on the dorso-lateral surface of the inferior peduncle; and (b) the ventral or accessory cochlear nucleus, placed between the two divisions of the nerve, on the ventral aspect of the inferior peduncle. ... The paired inferior colliculi together with the superior colliculi form the eminences of the corpora quadrigemina. ... The thalamus (from Greek θάλαμος = bedroom, chamber, IPA= /ˈθæləməs/) is a pair and symmetric part of the brain. ... A human brain. ... The primary auditory cortex is the region of the brain that is responsible for processing of auditory (sound) information. ... The temporal lobes are part of the cerebrum. ...


Associated anatomical structures include:

Image File history File links No higher resolution available. ...

Cochlear nucleus

Main article: Cochlear nucleus

The cochlear nucleus is the first site of the neuronal processing of the newly converted “digital” data from the inner ear. This region is anatomically and physiologically split into two regions, the dorsal cochlear nucleus (DCN), and ventral cochlear nucleus (VCN). The cochlear nuclei consist of: (a) the lateral cochlear nucleus, corresponding to the tuberculum acusticum on the dorso-lateral surface of the inferior peduncle; and (b) the ventral or accessory cochlear nucleus, placed between the two divisions of the nerve, on the ventral aspect of the inferior peduncle. ... The cochlear nuclei consist of: (a) the lateral cochlear nucleus, corresponding to the tuberculum acusticum on the dorso-lateral surface of the inferior peduncle; and (b) the ventral or accessory cochlear nucleus, placed between the two divisions of the nerve, on the ventral aspect of the inferior peduncle. ... The dorsal cochlear nucleus (DCN, also known as the tuberculum acousticum) differs from the ventral portion of the CN as it not only projects to the Inferior Colliculus (IC) but also receives efferent innervation from auditory cortex, superior olivary complex and inferior colliculus. ...


Trapezoid body

Main article: Trapezoid body

The Trapezoid body is a bundle of decussating fibers in the ventral pons that carry information used for binaural computations in the brainstem. The trapezoid body is part of the acoustic pathway. ... The trapezoid body is part of the acoustic pathway. ...


Superior olivary complex

The superior olivary complex is located in the pons, and receives projections predominantly from the ventral cochlear nucleus, although the posterior cochlear nucleus projects there as well, via the ventral acoustic stria. Within the superior olivary complex lays the lateral superior olive (LSO) and the medial superior olive (MSO). The former is important in detecting interaural intensity differences while the latter is important in distinguishing interaural time difference. For the cerebellar structure, see Dentate nucleus. ... For the cerebellar structure, see Dentate nucleus. ... For other uses, see Pons (disambiguation). ... For the cerebellar structure, see Dentate nucleus. ...

Lateral lemniscus in red, as it connects the cochlear nucleus, superior olivary nucleus and the inferior colliculus. Seen from behind.
Lateral lemniscus in red, as it connects the cochlear nucleus, superior olivary nucleus and the inferior colliculus. Seen from behind.

The cochlear nuclei consist of: (a) the lateral cochlear nucleus, corresponding to the tuberculum acusticum on the dorso-lateral surface of the inferior peduncle; and (b) the ventral or accessory cochlear nucleus, placed between the two divisions of the nerve, on the ventral aspect of the inferior peduncle. ... For the cerebellar structure, see Dentate nucleus. ... The paired inferior colliculi together with the superior colliculi form the eminences of the corpora quadrigemina. ...

Lateral lemniscus

Main article: lateral lemniscus

The lateral lemniscus is a tract of axons in the brainstem that carries information about sound from the cochlear nucleus to various brainstem nuclei and ultimately the contralateral inferior colliculus of the midbrain. The lateral lemniscus is a tract of axons in the brainstem that carries information about sound from the cochlear nucleus to various brainstem nuclei and ultimately the contralateral inferior colliculus of the midbrain. ... An axon or nerve fiber, is a long, slender projection of a nerve cell, or neuron, that conducts electrical impulses away from the neurons cell body or soma. ... The brain stem is the stalk of the brain below the cerebral hemispheres. ... The cochlear nuclei consist of: (a) the lateral cochlear nucleus, corresponding to the tuberculum acusticum on the dorso-lateral surface of the inferior peduncle; and (b) the ventral or accessory cochlear nucleus, placed between the two divisions of the nerve, on the ventral aspect of the inferior peduncle. ... The paired inferior colliculi together with the superior colliculi form the eminences of the corpora quadrigemina. ... In biological anatomy, the mesencephalon (or midbrain) is the middle of three vesicles that arise from the neural tube that forms the brain of developing animals. ...


Inferior colliculi

Main article: inferior colliculus

The IC are located just below the visual processing centers known as the superior colliculi. The central nucleus of the IC is a nearly obligatory relay in the ascending auditory system, and most likely acts to integrate information (specifically regarding sound source localization from the superior olivary complex and dorsal cochlear nucleus) before sending it to the thalamus and cortex. The paired inferior colliculi together with the superior colliculi form the eminences of the corpora quadrigemina. ... The paired inferior colliculi together with the superior colliculi form the eminences of the corpora quadrigemina. ... For the cerebellar structure, see Dentate nucleus. ... The dorsal cochlear nucleus (DCN, also known as the tuberculum acousticum) differs from the ventral portion of the CN as it not only projects to the Inferior Colliculus (IC) but also receives efferent innervation from auditory cortex, superior olivary complex and inferior colliculus. ...


Medial Geniculate Nucleus

The Medial Geniculate Nucleus is part of the thalamic relay system. The medial geniculate nucleus is a nucleus of the thalamus that acts as a relay for auditory information. ... The medial geniculate nucleus is a nucleus of the thalamus that acts as a relay for auditory information. ...


Primary auditory cortex

Primary Auditory Cortex is the first region of cerebral cortex to receive auditory input. The primary auditory cortex is the region of the brain that is responsible for processing of auditory (sound) information. ... The primary auditory cortex is the region of the brain that is responsible for processing of auditory (sound) information. ... For other uses, see Cortex. ...


Perception of sound is associated with the right posterior superior temporal gyrus (STG). The superior temporal gyrus contains several important structures of the brain, including Brodmann areas 41 and 42, marking the location of the primary auditory cortex, the cortical region responsible for the sensation of basic characteristics of sound such as pitch and rhythm. Superior temporal gyrus of the human brain. ... A Brodmann area is a region in the brain cortex defined by its cytoarchitectonic characteristics. ... The primary auditory cortex is the region of the brain that is responsible for processing of auditory (sound) information. ...


The auditory association area is located within the temporal lobe of the brain, in an area called the Wernicke's area, or area 22. This area, near the lateral cerebral sulcus, is an important region for the processing of acoustic signals so that they can be distinguished as speech, music, or noise. The temporal lobes are part of the cerebrum. ... Wernickes area is a part of the human brain that forms part of the cortex, on the left posterior section of the superior temporal gyrus, encircling the auditory cortex, on the Sylvian fissure (part of the brain where the temporal lobe and parietal lobe meet). ...


Bibliography

Kandel, et al Principles of Neuroscience. Fourth ed. pp 591-624. Copyright 2000, by McGraw-Hill Co.


See also

Sounds and noises are only separated by the experience of the listener. ... Roadway noise is the main source of exposure Noise health effects, the collection of health consequences of elevated sound levels, constitute one of the most widespread public health threats in industrialized countries. ... This article is about audible acoustic waves. ... Tinnitus (pronounced or ,[1] from the Latin word for ringing[2]) is the perception of sound in the human ear in the absence of corresponding external sound(s). ... Auditory Brainstem Response or Auditory Brainstem Response Audiometry is a screening test to monitor for hearing loss or deafness in newborn infants. ...

References

  1. ^ Meddean - CN VIII. Vestibulocochlear Nerve

External links

  • Promenade 'round the cochlea
  • Washington University Neuroscience Tutorial - Auditory system
The organ of Corti is the organ in the inner ear of mammals that contains auditory sensory cells, or hair cells. // Structure and function It has highly specialized structures that respond to fluid-borne vibrations in the cochlea with a shearing vector in the hairs of some cochlear hair cells. ... Section through the spiral organ of Corti. ... The basilar crest gives attachment to the outer edge of the basilar membrane; immediately above the crest is a concavity, the sulcus spiralis externus. ... On the upper plate of that part of the lamina which is outside the vestibular membrane, the periosteum is thickened to form the limbus laminæ spiralis, this ends externally in a concavity, the sulcus spiralis internus, which represents, on section, the form of the letter C. Histology at uc. ... The osseous spiral lamina consists of two plates of bone, and between these are the canals for the transmission of the filaments of the acoustic nerve. ... For other uses, see Brain (disambiguation). ... Covering the sulcus spiralis internus and the spiral organ of Corti is the tectorial membrane, which is attached to the limbus laminae spiralis close to the inner edge of the vestibular membrane. ... Hair cells are the sensory cells of both the auditory system and the vestibular system in all vertebrates. ... The spiral ganglion is the group of nerve cells that serve the sense of hearing by sending a representation of sound from the cochlea to the brain. ... The Cochlear nerve (n. ... The vestibulocochlear nerve (also known as the auditory or acoustic nerve) is the eighth of twelve cranial nerves, and is responsible for transmitting sound and equilibrium (balance) information from the inner ear to the brain. ... The cochlear nuclei consist of: (a) the dorsal cochlear nucleus, corresponding to the tuberculum acusticum on the dorso-lateral surface of the inferior peduncle; and (b) the ventral or accessory cochlear nucleus, placed between the two divisions of the nerve, on the ventral aspect of the inferior peduncle. ... The trapezoid body is part of the acoustic pathway. ... For the cerebellar structure, see Dentate nucleus. ... The lateral lemniscus is a tract of axons in the brainstem that carries information about sound from the cochlear nucleus to various brainstem nuclei and ultimately the contralateral inferior colliculus of the midbrain. ... The paired inferior colliculi together with the superior colliculi form the eminences of the corpora quadrigemina. ... The medial geniculate nucleus is a nucleus of the thalamus that acts as a relay for auditory information. ... The primary auditory cortex is the region of the brain that is responsible for processing of auditory (sound) information. ... The vestibular system, or balance system, is the sensory system that provides the dominant input about movement and equilibrioception. ... The utricle, larger than the saccule, is of an oblong form, compressed transversely, and occupies the upper and back part of the vestibule, lying in contact with the recessus ellipticus and the part below it. ... The portion of the utricle which is lodged in the recess forms a sort of pouch or cul-de-sac, the floor and anterior wall of which are thickened, and form the macula of utricle, which receives the utricular filaments of the acoustic nerve. ... Categories: Stub ... The saccule is the smaller of the two vestibular sacs; it is globular in form, and lies in the recessus sphæricus near the opening of the scala vestibuli of the cochlea. ... From the posterior wall of the saccule a canal, the ductus endolymphaticus, is given off; this duct is joined by the ductus utriculosaccularis, and then passes along the aquaeductus vestibuli and ends in a blind pouch, the endolymphatic sac, on the posterior surface of the petrous portion of the temporal... From the posterior wall of the saccule a canal, the endolymphatic duct, is given off; this duct is joined by the ductus utriculosaccularis, and then passes along the aquaeductus vestibuli and ends in a blind pouch (saccus endolymphaticus) on the posterior surface of the petrous portion of the temporal bone... A kinocilium is a special structure connected to the hair cells of the inner ears cochlea. ... An otolith, (oto-, ear + lithos, a stone), also called statoconium[1] or otoconium is a structure in the saccule or utricle of the inner ear, specifically in the vestibular labyrinth. ... inner ear illustration showing semicircular canal, hair cells, ampulla, cupula, vestibular nerve, & fluid The semicircular canals are three half-circular, interconnected tubes located inside each ear that are the equivalent of three gyroscopes located in three planes perpendicular (at right angles) to each other. ... The introduction to this article provides insufficient context for those unfamiliar with the subject matter. ... The posterior semicircular canal, vertical like the superior, is directed backward, nearly parallel to the posterior surface of the petrous bone; it is the longest of the three canals, measuring from 18 to 22 mm. ... The lateral or horizontal canal (external semicircular canal) is the shortest of the three canals. ... The cupula forms the apex of the cochlea. ... The bony semicircular canals are three in number, superior, posterior, and lateral, and are situated above and behind the vestibule. ... This article does not cite any references or sources. ... For other uses, see Brain (disambiguation). ... The vestibular nerve is one of the two branches of the Vestibulocochlear nerve (the cochlear nerve is the other. ... The vestibulocochlear nerve (also known as the auditory or acoustic nerve) is the eighth of twelve cranial nerves, and is responsible for transmitting sound and equilibrium (balance) information from the inner ear to the brain. ... The nuclei of the vestibular nerve. ... Figure 1a: A human brain, with the cerebellum in purple. ... The nuclei of the vestibular nerve. ... The vestibulospinal tract is one of the descending spinal tracts of the ventromedial pathway. ... The ventral posterolateral nucleus (VPL) is a nucleus of the thalamus which projects to the postcentral gyrus and receives information from the medial lemniscus. ... The nervous system is a highly specialized network whose principal components are nerves called neurons. ... The human eye is the first element of a sensory system: in this case, vision, for the visual system. ... This article is about the senses of living organisms (vision, taste, etc. ... The traditional five senses in human kind are the senses of vision, hearing, taste, and smell, and touch. ... The visual system is the part of the nervous system which allows organisms to see. ... In psychology, visual perception is the ability to interpret information from visible light reaching the eyes. ... Hearing (or audition) is one of the traditional five senses, and refers to the ability to detect sound. ... A Chemosensor, also known as chemoreceptor, is a cell or group of cells that transduce a chemical signal into an action potential. ... The olfactory system is the sensory system used for olfaction. ... Olfaction (also known as olfactics) refers to the sense of smell. ... The gustatory system is the sensory system that uses taste buds (or lingual papillae) on the upper surface of the tongue to provide information about the taste of food being eaten. ... Taste (or, more formally, gustation) is a form of direct chemoreception and is one of the traditional five senses. ... Touch redirects here. ... A nociceptor is a sensory receptor that sends signals that cause the perception of pain in response to potentially damaging stimulus. ... A thermoreceptor is a sensory receptor that responds to temperature, primarily within the innocuous range. ... The vestibular system, or balance system, is the sensory system that provides the dominant input about movement and equilibrioception. ... A mechanoreceptor is a sensory receptor that responds to mechanical pressure or distortion. ... This article is about pressure in the physical sciences. ... Oscillation is the variation, typically in time, of some measure about a central value (often a point of equilibrium) or between two or more different states. ... // Proprioception (PRO-pree-o-SEP-shun (IPA pronunciation: ); from Latin proprius, meaning ones own and perception) is the sense of the relative position of neighbouring parts of the body. ... In a sensory system, a sensory receptor is a structure that recognizes a stimulus in the internal or external environment of an organism. ...

  Results from FactBites:
 
ScienceDaily: Auditory system (1400 words)
The auditory system is the sensory system for the sense of hearing.
Auditory system -- The auditory system is the sensory system for the sense of hearing.
A sensory system consists of sensory receptors, neural pathways, and parts of the brain involved in...
Auditory System (1861 words)
Nerve impulses are transmitted from the ear to the brain via the auditory nerves, one of the several sensory nerves that exists in the group of nerves known as cranial nerves.
The auditory nerves connect the nerve impulses of the ears to the upper "temporal lobe" of the "cerebral cortex".
Auditory cognition analyzes such issues as attending to auditory events, remembering and recognizing sound sources and events, and perceptions of acoustic sequences.
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