cochlear nerve

(noun)

A sensory nerve that conducts information about the environment to the brain, in this case acoustic energy impinging on the tympanic membrane (sound waves reaching the ear drum). The cochlear nerve arises from within the cochlea and extends to the brainstem where its fibers make contact with the cochlear nucleus, the next stage of neural processing in the auditory system.

Related Terms

Examples of cochlear nerve in the following topics:

  • Vestibulocochlear (VIII) Nerve

    • The vestibulocochlear nerve (cranial nerve VIII) carries information about hearing and balance.
    • The vestibulocochlear nerve (also known as the auditory vestibular nerve and cranial nerve VIII) has axons that carry the modalities of hearing and equilibrium.
    • It consists of the cochlear nerve that carries information about hearing, and the vestibular nerve that carries information about balance.
    • The vestibulocochlear nerve consists mostly of bipolar neurons and splits into two large divisions: the cochlear nerve and the vestibular nerve.
    • The cochlear nerve travels away from the cochlea of the inner ear where it starts as the spiral ganglia.

  • Transduction and Perception

    • When a sound causes the stereocilia to move, mechanosensitive ion channels transduce the signal to the cochlear nerve.

  • Pons

    • The alar plate produces sensory neuroblasts, which will give rise to the solitary nucleus and its special visceral afferent column, the cochlear and vestibular nuclei (which form the special somatic afferent fibers of the vestibulocochlear nerve), the spinal and principal trigeminal nerve nuclei (which form the general somatic afferent column of the trigeminal nerve), and the pontine nuclei, which is involved in motor activity.
    • Basal plate neuroblasts give rise to the abducens nucleus (forms the general somatic efferent fibers), the facial and motor trigeminal nuclei (form the special visceral efferent column), and the superior salivatory nucleus, which forms the general visceral efferent fibers of the facial nerve.
    • A number of cranial nerve nuclei are present in the pons:
    • The chief or pontine nucleus of the trigeminal nerve sensory nucleus (V)- mid-pons
    • The functions of the four nerves of the pons include sensory roles in hearing, equilibrium, taste, and facial sensations such as touch and pain.

  • Transduction of Sound

    • When sound waves reach the ear, the ear transduces this mechanical stimulus (pressure) into a nerve impulse (electrical signal) that the brain perceives as sound.
    • When the sound waves in the cochlear fluid contact the basilar membrane, it flexes back and forth in a wave-like fashion.
    • As a result, the hair cell membrane is depolarized, and a signal is transmitted to the chochlear nerve.
    • The cochlear branch of the vestibulocochlear cranial nerve sends information on hearing.
    • Movement of stereocilia on hair cells results in an action potential that travels along the auditory nerve.

  • Development of Hearing and Balance

    • The vestibular wall will separate the cochlear duct from the perilymphatic scala vestibuli, a cavity inside the cochlea.
    • The basilar membrane separates the cochlear duct from the scala tympani, a cavity within the cochlear labyrinth.
    • The lateral wall of the cochlear duct is formed by the spiral ligament and the stria vascularis, which produces the endolymph.
    • The hair cells develop from the lateral and medial ridges of the cochlear duct, which together with the tectorial membrane make up the organ of Corti.
    • First reports on critical periods came from studies of deaf children and animals that received a cochlear implant to restore hearing.

  • The Vestibular System

    • It is the vestibular branch of the vestibulocochlear cranial nerve that deals with balance.
    • Hair cells from the utricle, saccule, and semicircular canals also communicate through bipolar neurons to the cochlear nucleus in the medulla.
    • Cochlear neurons send descending projections to the spinal cord and ascending projections to the pons, thalamus, and cerebellum.

  • Trochlear (IV) Nerve

    • The trochlear nerve (cranial nerve IV) is a motor nerve that innervates a single muscle: the superior oblique muscle of the eye.
    • The trochlear nerve (cranial nerve IV) is a motor nerve that innervates a single muscle: the superior oblique muscle of the eye.
    • The trochlear nerve is unique among the cranial nerves in several respects.
    • Other than the optic nerve (cranial nerve II), it is the only cranial nerve that decussates (crosses to the other side) before innervating its target.
    • Lesions of all other cranial nuclei affect the ipsilateral side (except of course the optic nerve, cranial nerve II, which innervates both eyes).

  • Accessory (XI) Nerve

    • The accessory nerve (cranial nerve XI) controls the muscles of the shoulder and neck.
    • The accessory nerve (cranial nerve XI) controls the sternocleidomastoid and trapezius muscles of the shoulder and neck.
    • Unlike the other 11 cranial nerves, the accessory nerve begins outside the skull.
    • Due to its unusual course, the accessory nerve is the only nerve that enters and exits the skull.
    • However, more modern characterizations of the nerve regard the cranial component as separate and part of the vagus nerve.

  • Brief Overview of Cranial Nerves

    • Cranial nerves are the nerves that emerge directly from the brain (including the brainstem).
    • The terminal nerves, olfactory nerves (I) and optic nerves (II) emerge from the cerebrum or forebrain, and the remaining ten pairs arise from the brainstem, which is the lower part of the brain.
    • The optic nerve (II): This nerve carries visual information from the retina of the eye to the brain.
    • The abducens nerve (VI): A motor nerve that innervates the lateral rectus muscle of the eye, which controls lateral movement.
    • The hypoglossal nerve (XII): This nerve controls the tongue movements of speech, food manipulation, and swallowing.

  • Olfactory (I) Nerve

    • The olfactory nerve, or cranial nerve I, is the first of 12 cranial nerves and is responsible for the sense of smell.
    • The olfactory nerve, or cranial nerve I, is the first of the 12 cranial nerves.
    • The olfactory nerve is the shortest of the 12 cranial nerves and only one of two cranial nerves (the other being the optic nerve) that do not join with the brainstem.
    • The specialized olfactory receptor neurons of the olfactory nerve are located in the olfactory mucosa of the upper parts of the nasal cavity.
    • The olfactory nerves consist of a collection of many sensory nerve fibers that extend from the olfactory epithelium to the olfactory bulb, passing through the many openings of the cribriform plate of the ethmoid bone.