Vestibulocochlear Nerve(redirected from eighth cranial nerve)
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vestibulocochlear nerve[və¦stib·yə·lə′käk·lē·ər ‚nərv]
in man, the eighth pair of cranial nerves.
The nerve copsists of two functional parts— the vestibular, which is the conductor of the impulses from the organ of equilibrium, and the cochlear, which perceives auditory stimuli. The vestibular part begins from the vestibular ganglion, which lies on the floor of the internal auditory canal. The peripheral processes of the nerve cells of that ganglion approach the receptor elements of the sacculus, utriculus, and ampulla of the membranous semicircular canals of the inner ear. The cochlear part originates from the spiral ganglion at the base of the bony plate of the cochlea. The peripheral processes of the cells of that ganglion enter into close contact with the receptor apparatus of the spiral organ (organ of Corti), which is located along the entire length of the cochlear canal of the membranous labyrinth. The central processes of the vestibular and spiral ganglia emerge from the inner ear and, as the corresponding parts of the nerve, are directed to the base of the brain. Outside the olivary nucleus of the medulla oblongata the central processes enter the base of the brain and, after uniting, reach their nuclei, which are localized in the corners of the rhomboid fossa.
With infectious or traumatic disorders of the fibers of the cochlear portion of the vestibulocochlear nerve, hearing disorders and even deafness may result. When there are disturbances of the vestibular portion, there is disruption of equilibrium and dizziness.