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Neuro > Vestibular System (CN VIII) > Flashcards

Vestibular System (CN VIII) Flashcards

1
Q

What are the three roles of the vestibular system?

A

1) Sensory- regulates eye movement and focus during head movement
2) Influences muscle tone in axial and appendicular skeleton for control of postural support and balance
3) Provide conscious awareness of spatial orientation

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2
Q

What separates the temporal bone cavity from the membranous labyrinth?

A

Fluid called perilymph

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3
Q

Each bony labyrithn contains and end organ which contains…

A

membranous labyrinth, series of tubes made from membranes that contain hair cells.

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4
Q

The five sites that contain hair cells are…

A

each of the 3 semicircular canals, the utricle, the saccule.

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5
Q

The horizontal canal is horizontal when head is… and is activated when head rotates…

A

flexed 30 degrees; around body axis

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6
Q

Anterior and posterior canals are activated with rotation in…

A

oblique orientation between frontal and sagittal planes

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7
Q

What is the dynamic function of the semicircular canals?

A

To detect angular velocity of the head in all 3 planes which is especially important for stabilizing the eyes during head movement

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8
Q

What are hair cells in the ampulla called

A

Crista

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9
Q

What innervates the hair cells?

A

Peripheral end of the vestibular nerve

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10
Q

Hair cells protrude upwards into a gelatinous material called the…

A

cupula

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11
Q

What is the resting discharge rate of hair cells?

A

100-300 spikes per second

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12
Q

Depolarization occurs when the stereo cilium bend towards the…

A

kinocilium

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13
Q

Depolarization causes an increase in … of already tonically active nerve when the stereo cilium bend toward the kinocilium.

A

firing

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14
Q

What restored the resting position of the hair cells?

A

Spring-like action of the cupula

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15
Q

Semi circular canals are fast/slow adapting receptors with a low/high threshold and produce a graded/tonic response

A

Fast; low; graded

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16
Q

The otholitic organ is made of the … and the …

A

saccule; utricle

17
Q

Function of the otoliths?

A

detect liner acceleration and deceleration of the head and encoding static position of head. Maintain head upright and modulate muscle tone to hold head upright

18
Q

Are BOTH ends of the semicircular canals continuous with the utricle?

A

Yes, but not the saccule

19
Q

Overproduction of endolymph causes what symptoms?

A

Auditory disturbances, severe vertigo, nausea, nystagmus (Menieres dz)

20
Q

What is a macula?

A

Sensory organ on wall of utricle and saccule

21
Q

What covers the macula?

A

Gelatinous layer with embedded small crystals calcium carbonate called OTOCONIA.

22
Q

What do the macula synapse with?

A

Sensory axons of vestibular nerve

23
Q

The macula of the utricle is positioned ho/vert while the macula of the saccule is positioned ho/vert

A

ho; vert

24
Q

What type of movement causes discharge in specific parts of the macula?

A

Head tilt

25
Q

Are the macula fast adapting or non adapting? The they fire constantly?

A

Non-adapting, the respond at all times

26
Q

What is benign paroxysmal positional vertigo (BPPV)?

A

Otoconio from macula dislodge and float into semicircular canal, usually posterior semicircular. The floating debris stimulates the hair cells and causes vertigo, nystagmus and nausea.

27
Q

What type of nerve is CN VII Vestibulocochlear?

A

Bipolar

28
Q

What do the cell bodies of CN VII Vestibulocochlear form?

A

Scarpa’s ganglion, located near internal auditory meatus

29
Q

What happens after these nerve fibers join the cochlear fibers? Where do they enter the brainstem?

A

Travel in internal auditory canal with facial nerve, pass through temporal bone into posterior fossa, enter brainstem at pontomedullary junction

Neuro (2 decks)

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