498
UNIT 3
Regulation and Integration of the Body
13
Temporal
Zygomatic
Buccal
Mandibular
Cervical
(c) A simple way to remember the courses of the five
major branches of the facial nerve
Vestibulocochlear nerve (VIII)
Pons
Cochlear nerve
Vestibular nerve
Internal acoustic
meatus
Vestibular
ganglia
Semicircular
canals
Vestibule
Cochlea
(containing
spiral ganglion)
VII Facial Nerves
(continued)
VIII Vestibulocochlear Nerves
(ves-tib
0
u-lo-kok
9
le-ar)
Origin and course:
Fibers arise from
hearing and equilibrium apparatus
located within inner ear of temporal
bone and pass through internal
acoustic meatus to enter brain stem
at pons-medulla border. Afferent
fibers from hearing receptors in
cochlea form the
cochlear division
;
those from equilibrium receptors
in semicircular canals and vestibule
form the
vestibular division
(vestibular nerve). The two divisions
merge to form vestibulocochlear
nerve. See also Figure 15.26.
Function:
Mostly sensory. Vestibular
branch transmits afferent impulses
for sense of equilibrium, and sensory
nerve cell bodies are located in
vestibular ganglia
. Cochlear branch
transmits afferent impulses for sense of
hearing, and sensory nerve cell bodies
are located in
spiral ganglion
within
cochlea. Small motor component
adjusts the sensitivity of sensory
receptors. See also Figure 15.27.
Clinical testing:
Check hearing by air
and bone conduction using tuning
fork.
Homeostatic
Imbalance
Lesions of cochlear
nerve or cochlear receptors result in
central
, or
nerve
,
deafness
. Damage to
vestibular division produces dizziness,
rapid involuntary eye movements, loss of
balance, nausea, and vomiting.
Table 13.2
Cranial Nerves
(continued)
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