The vestibulocochlear nerve, known as the eighth cranial nerve, transmits
sound and equilibrium information from the inner ear to the brain.
Structure 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. Processes from
the organ of Corti conduct afferent transmission to the spiral ganglia. It
is the inner hair cells of the organ of Corti that are responsible for
activation of afferent receptors in response to pressure waves reaching the
basilar membrane through the transduction of sound. The exact
mechanism by which sound is transmitted by the neurons of the cochlear nerve is
uncertain; the two competing theories are place theory and temporal theory.
The vestibular nerve travels from the vestibular system of the inner ear. The
vestibular ganglion houses the cell bodies of the bipolar neurons and
extends processes to five sensory organs. Three of these are the cristae
located in the ampullae of the semicircular canals. Hair cells of the
cristae activate afferent receptors in response to rotational acceleration. The
other two sensory organs supplied by the vestibular neurons are the maculae of
the saccule and utricle. Hair cells of the maculae in the utricle activate
afferent receptors in response to linear acceleration while hair cells of the
maculae in the saccule respond to vertically directed linear force.
= Development = The vestibulocochlear nerve is derived
from the embryonic otic placode. Function
This is the nerve along which the sensory cells of the inner ear transmit
information to the brain. It consists of the cochlear nerve, carrying information
about hearing, and the vestibular nerve, carrying information about balance. It
emerges from the pontomedullary junction and exits the inner skull via the
internal acoustic meatus in the temporal bone.
The vestibulocochlear nerve carries axons of type SSA, special somatic
afferent, which carry the modalities of hearing and equilibrium.
Clinical significance = Symptoms of damage =
Damage to the vestibulocochlear nerve may cause the following symptoms:
hearing loss vertigo
false sense of motion loss of equilibrium
nystagmus motion sickness
gaze-evoked tinnitus. = Examination =
History = Etymology =
Some older texts call the nerve the acoustic or auditory nerve, but these
terms have fallen out of widespread use because they fail to recognize the
nerve's role in the vestibular system. Vestibulocochlear nerve is therefore
preferred by most. See also
Auditory system References
Additional images External links
MedEd at Loyola GrossAnatomycncn8.htm cranialnerves at The Anatomy Lesson by
Wesley Norman Notes on Vestibulocochlear Nerve