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Anatomy of the VIII Nerve
Study for Exam 2
46
Audiology
Undergraduate 3
10/24/2009

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Term
The VIIIth Cranial Nerve is AKA...
Definition
The Vestibulocochlear Nerve
Term
What are the two portions of the VIIIth Cranial Nerve?
Definition
The Cochlear Portion and the Vestibular Portion
Term
The cochlear portion of the VIIIth Cranial Nerve comes from...
Definition
the sensory cells of the cochlea.
Term
The vestibular portion of the VIIIth Cranial Nerve comes from...
Definition
The sensory cells of the vestibular system.
Term
Which portion of the VIIth cochlear nerve travels as the Spiral Ganglion cells from the Organ of Corti to the modiolus?
Definition
The cochlear portion.
Term
The cochlear portion of the VIIIth Cranial Nerve travels...
Definition
as the spiral ganglion cells from the Organ of Corti to the modiolus joining the vestibular portion as it enters the IAM.
Term
Which portion of the VIIIth Cranial Nerve travels from the sensory cells of all vestibular organs (Ampulla and Macula)
Definition
The Vestibular portion
Term
Where do the Cochlear and Vestibular portions of he VIIIth Nerve meet?
Definition
At the entrance of the Internal Auditory Meatus (IAM).
Term
The Vestibular portion is also known as...
Definition
Scarpa's Ganglion
Term
The vestibular portion of the VIIIth nerve travels...
Definition
from the sensory cells of all vestibular organs (Ampulla and Macula), and joins the cochlear portion of the VIIIth nerve and enters the Internal Auditory Meatus.
Term
Which other nerve also travels with the VIIIth cranial nerve in the IAM?
Definition
The Facial Nerve (VIIth Cranial Nerve)
Term
VIIIth Nerve Spiral
Definition
Auditory fibers spiral through the internal auditory meatus. It is a cable or bundle of fibers in which the basal or high frequency fibers are found on the outside of the bundle, and the low frequency or apical fibers are found on the inside of the bundle
Term
Approximately how long is the internal auditory meatus in adults?
Definition
10mm
Term
Through what does the VIIth nerve spiral travel?
Definition
The Internal Auditory Meatus
Term
Aside from the VIII auditry nerve spiral what else does the IAM carry?
Definition
The Internal Auditory Artery
Term
The VIIIth nerve extends 17 to 19mm beyond the internal auditory canal, where it attaches to...
Definition
the brainstem at a juncture of the cerebellum, medulla oblongata and the pons called the CEREBELLOPONTINE ANGLE
Term
CEREBELLOPONTINE ANGLE
Definition
on the brainstem, a juncture of the cerebellum the medulla oblongata and the pons where the VIII Nerve attaches.
Term
The nerve fibers that innervate the Outer
Hair Cells and Inner Hair Cells of the Organ of
Corti are both...
Definition
Afferent (sensory) and Efferent
(motor)
Term
The function of Afferent (sensory) Fibers?
Definition
to take sensory information from the periphery into the CNS
Term
The function of efferent auditory nerve fibers is to...
Definition
provide motor innervation from the CNS out to the periphery
Term
What do we mean when we say that Afferent auditory verve fibers are bipolar?
Definition
they have a peripheral and a central
axon
Term
AXON
Definition
An axon or nerve fiber is a long, slender projection of a nerve cell, or neuron, that conducts electrical impulses away from the neuron's cell body or soma.
Term
Dendrite
Definition
the branched projections of a neuron that act to conduct the electrochemical stimulation received from other neural cells to the cell body, or soma, of the neuron from which the dendrites project
Term
The more peripheral axon of a bipolar auditory fiber can also be called?
Definition
A Dendrite.
Term
Unlike dendrites both peripheral and central axons are...
Definition
myelinated
Term
The dendrite conducts...
Definition
action
potentials, which move across the cell body,
and continue to propagate along the central
axon
Term
How many types of afferent bipolar spiral ganglion cells are there?
Definition
TWO: Type I and Type II
Term
Type I account for what percentage of the spiral ganglion cells?
Definition
90%
Term
Type I Cells
Definition
account for 90% of the spiral ganglion cells. They are large, myelinated, and primarily attach to the IHCs; central axon attaches to the cochlear nucleus.
Term
Cochlear Modiolus
Definition
a conical shaped central axis in the cochlea. The Modiolus consists of spongy bone and the cochlea turns approximately 2.75 times around the modiolus The spiral ganglion is situated inside the bony modiolus.
Term
The spiral ganglion is situated inside the
Definition
cochlear modiolus
Term
Spiral ganglion
Definition
he group of nerve cells that serve the sense of hearing by sending a representation of sound from the cochlea to the brain.

ound in the spiral ganglion are strung along the bony core of the cochlea, and send projections into the central nervous system (CNS).
Term
The internal auditory canal begins at the____ and ends at the _____
Definition
cochlear modiolus
base of the brain
Term
Type II neurons account for what percentage of the spiral ganglion cells/
Definition
10%
Term
Type II Neurons
Definition
are small, unmyelinated, and connect to OHCs; central axon attaches to cochlear nucleus.
Term
The majority of the nerve fibers of the VIII nerve are what type of fibers/
Definition
Afferent/Sensory aprox. 30,000
Term
There are aprox how many efferent (motor) cochlear fibers that travel primarily from the brainstem to the OHC's
Definition
1200
Term
Afferent fibers enter the cochlea through...
Definition
the habenula perforata
Term
Type I Fibers synapse on each IHC in what type of pattern?
Definition
a many-to -one pattern
Term
Type II fibers cross the tunnel of corti to the OHC's in what type of pattern
Definition
one-to-many pattern
Term
The cell bodies of efferent fibers are located in the brainstem primarily at...
Definition
the level of the contralateral superior olivary complex.
Term
The efferent fibers travel as a group called the
Definition
Olivocochlear bundle
Term
Efferent fibers connect primarily to which type of hair cell?
Definition
OHC's
Term
For IHC's the efferent fibers primarily contact the...
Definition
afferent fiber dendrites, not he IHC's directly.
Term
For OHC's efferent and afferent fibers both contact...
Definition
The OHC's directly
Term
[image]
Definition
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