Hearing and balance: The eighth cranial nerve (Chapter 14)

Question 1

What is the eighth cranial nerve?

Answer 1

CNVIII = vestibulocochlear nerve.

Question 2

Where are auditory and vestibular receptors found?

Answer 2

In the membraneous labyrinth of the ear

Question 3

What is the cochlear division’s function and what is it sensitive to?

Answer 3

Hearing; air-borne vibration

Question 4

What is the vestibular division’s function and what is it sensitive to?

Answer 4

Balance; head acceleration (linear, angular)

Question 5

What type of fibers are contained in the vestibulocochlear nerve?

Answer 5

Special sensory fibers

Question 6

Where is the membraneous labyrinth located?

Answer 6

The membraneous labyrinth is suspended within the bony labyrinth.

Question 7

Where is the bony labyrinth located?

Answer 7

It is part of the petrous portion of the temporal bone.

Question 8

Name the parts of the bony labyrinth.

Answer 8

Cochlea, vestibule, oval window, round window, endolymphatic sac, semicircular canals (anterior, posterior, horizontal).

Question 9

Where are hair cells located in the membraneous labyrinth?

Answer 9

Hair cells are located in the cochlear duct, the vestibule (saccule, utricle), and the semicircular ducts (anterior, horizontal, posterior, ampulla of the posterior)

Question 10

Describe the flow of endolymph through the membraneous labyrinth.

Answer 10

The endolymph system has a system of production, circulation, and absorption, like the CSF in ventricles.
Flows from the cochlea to the saccule, from the ducts to the utricle, to the endolymphatic duct and into the endolymphatic sac where it is reabsorbed.

Question 11

Swelling of of the membraneous membrane (endolymphatic hydrops) can cause transient attacks of vertigo, nausea, and hearing loss/tinnitus. What is the name of this syndrome?

Answer 11

Ménière’s disease

Question 12

Perilymph :: ____ as Endolymph :: _____.

Answer 12

Perilymph :: CSF as Endolymph :: intracellular fluid.

Question 13

Hair cells are ______receptors.

Answer 13

Hair cells are mechanoreceptors.

Question 14

Hair cell microvillae are known as the…

Answer 14

Stereocilia

Question 15

The _____ of the hair cell is the tallest, and single true cilium is known as the…

Answer 15

Kinocilium

Question 16

The ________ space is continuous with the ______ via a small canal in the temporal bone,

Answer 16

Subarachnoid space; perilymph

Question 17

How do hair cells produce receptor potentials?

Answer 17

Stereocilia are rigid and embedded in gelatinous material. They pivot (not bend) in concert in response to mechanical deformation.

Question 18

How do hair cells produce receptor potentials (generally speaking)?

Answer 18

Stereocilia are rigid and embedded in gelatinous masses. They pivot (not bend) in concert at their junction with the cell, in response to mechanical deformation. Movement of the gelatinous mass relative to the hair cells causes deflection of stereocilia, which in turn causes a receptor potential.

Question 19

What is the critical variable determining which type of stimuli hair cells are most sensitive to (sound, head movement, or head position)?

Answer 19

The critical variable determining whether hair cells are sensitive to sound, head movement, or head position is variation in the physical coupling of the gelatinous mass and stereocilia.

Question 20

Hair cells that are sensitive to SOUND are located in the ______ in the _____ (part of the labyrinth), and their gelatinous material is _______.

Answer 20

Hair cells that are sensitive to SOUND are located in the Organ of Corti in the cochlea, and their gelatinous material is tectorial membrane.

Question 21

Hair cells that are sensitive to ANGULAR ACCELERATION are located in the ______ in the _____ (part of the labyrinth), and their gelatinous material is _______.

Answer 21

Hair cells that are sensitive to ANGULAR ACCELERATION are located in the cristae in the semicircular ducts, and their gelatinous material is cupula.

Question 22

Hair cells that are sensitive to LINEAR ACCELERATION are located in the ______ in the _____ and ______ (part of the labyrinth), and their gelatinous material is _______.

Answer 22

Hair cells that are sensitive to LINEAR ACCELERATION are located in the maculae in the utricle and saccule, and their gelatinous material is otolithic membrane.

Question 23

Hair cells share a common mechanism of transduction. What is it?

Answer 23

Deflection of the stereocilium,
> Cation channels open,
>> K+ goes in,
>>> CA^2 goes out,
>>>> Glutamate is released,
>>>>> Increased firing rate.

Question 24

How is sound transduced (generally speaking)?

Answer 24

The outer and middle ear convey air-borne vibrations to the fluid filled inner ear via middle ear ossicles (malleus, incus, and stapes).