Vestibular system

Question 1

What is labyrinth of inner ear composed of?

Answer 1

Cochlea
Vestibule
semicircular canals

Question 2

What does vestibular system function in?

Answer 2

Maintenance of posture, muscle tone, and eye position with respect to head motion.

Question 3

Where are vestibular nuclei located?

Answer 3

In lateral aspect of floor of medullary and pontine part of 4th ventricle - underlying vestibular area

Question 4

Where do axons from vestibular nuclei project to?

Answer 4

Flocculonodular lobe and fastigial nucleus of cerebellum
Spinal cord in VST
Brain stem nuclei of CN III, IV, and VI bilaterally via MLF
Fibers from vestibular nuclei ascend to ventral posterior thalami’s nucelus and to other parietal association areas of cortex

Question 5

What is internuclear opthalmoplegia?

Answer 5

Failure of CN III, IV, and VI to carry out synchronous horizontal gaze due to MLF lesion.

Question 6

What is barany chair vestibular exam?

Answer 6

Rotate 10x in 20 seconds where pt flexes forward 30 degrees and rotation stops abruptly. Intact system produces nystagmus opposite of rotation.

Question 7

what is caloric testing vestibular exam?

Answer 7

Warm or cold water in external acoustic meatus. Cold = nystagmus to opposite side of irrigation.
Warm water= nystagmus to same side in intact vestibular system

Question 8

What does vestibule of inner ear labyrinth composed of?

Answer 8

Utricle
Saccule

Question 9

What is vestibular system subdivided into?

Answer 9

Static labyrinth and kinetic labyrinth

Question 10

What is kinetic labrynith composed of?

Answer 10

Semicircular canals
Crista ampullaris
Cupula

Question 11

What do semicircular canals do in the kinetic labrynith?

Answer 11

Orthogonally oriented to detect all possible directions of motion.

Question 12

What are the crista ampullaris?

Answer 12

The specialized hair cells in the semicircular canals in the ampullae

Question 13

What is the cupula?

Answer 13

Gelatinous mass that the hair cells in the crista ampullaris are embedded in

Question 14

What do the utricle and saccule do in the static labrynith?

Answer 14

Detect static orientation of head with respect to gravity.

Question 15

What are the specialized hair cells in the static labrynith called?

Answer 15

Macula utricle and macula succuli

Question 16

What are hair cells in maculae embedded in?

Answer 16

A gelatinous mass, the otolithic membrane which contains. CaCO3 crystals

Question 17

What are symptoms of vestibular lesions?

Answer 17

Vertigo, nystagmus, and dysequlibrium.

Question 18

Central lesions may produce what?

Answer 18

Nystagmus in various directions in absence of vertigo during positional testing

Question 19

Peripheral lesion causes what?

Answer 19

Horizontal nystagmus only in prescence of vertigo

Question 20

What is an acoustic neuroma or schwannoma?

Answer 20

A relatively common benign slow growing Schwann cell tumor of vestibular nerve. Typically found in region of internal acoustic meatus or cerebellopontine angle.
Can affect facial and trigeminal nerves.

Question 21

What is Ménière’s disease?

Answer 21

Vestibular symptoms such as equilibrium loss, nystagmus and vertigo accompany progressive loss of hearing and tinnitus. Onsets 20-30 years of age

Question 22

What causes hair cell depolarization?

Answer 22

Potassium influx

Question 23

What happens when microvilli bend toward kinocilium?

Answer 23

The cell will depolarize

Question 24

When the microvilli move away what happens to the cell?

Answer 24

The cell will hyperpolarize

Question 25

Describe hair cells

Answer 25

Have microvilli on one end with a longer kinocilium on the opposite end