Vestibular System Flashcards by Catherine Parkhurst

What are the tasks of the vestibular system? (2)

1 Which was is up?

2 Where am I going?

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What is the dynamic function of the vestibular system?

Sensing movement through space

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What is the static function of the vestibular system?

Sensing head position

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What two types of acceleration can the vestibular system detect?

Angular/rotational

Linear

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What is the function of the vestibulo-ocular reflex?

Keep the eyes still when the head moves

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What is the function of the vestibulospinal reflex?

Enable the skeletomotor system to compensate for head movements

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What are symptoms of disease of vestibular system?

Vertigo
Nausea/vomiting/perspiration
Difficulty walking
Spinning
Nystagmus: horizontal eye mvmt
Oscillopsia: spinning world/room

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Which fluid, endolymph or perilymph, is rich in K+?

Endolymph

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What happens when volumes of endolymph or perilymph get too large?

Vestibular and auditory symptoms

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What is Meniere’s Disease?

excessive endolymph production in the inner ear

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How do we treat Meniere’s disease?

Shunts to drain, steroids

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How does a labyrinthine infarction occur?

Thrombotic narrowing of AICA or basilar artery

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What is a labyrinthine infarction associated with?

infarction of the brainstem/cerebellum

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What do the semicircular canals detect?

Angular acceleration

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What do the otolithic organs detect?

linear acceleration (dynamic)
position of the head (static)

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How do the semicircular canals work in pairs?

Horizontal together

Superior/Posterior together

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What does the ampulla contain?

ampullary crest: thickened epithelium of hair cells

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What is the cupula?

a gelatinous mass that covers the ampullary crest, weighs it down!

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What is the function of the ampulla?

To detect angular acceleration

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How are hair cells organized?

All kinociliums face the same direction

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What happens when the stereocilia move away vs. toward the kinocilium?

Toward: depol
Away: hyperpol

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What is the function of the utricle?

Detect movement in the horizontal plane

What is the macula of the utricle?

thickened epithelium oriented in the horiz. plane containing hair cells

What special item is embedded in the macula? What is their function?

Calcium carbonate crystals that bend the stereocilia

What does the utricle/macula respond best to?

Linear acceleration

What is the macula of the saccule?

Thickened epithelium oriented in the vertical plane

What does the saccule/macula respond best to?

linear acceleration in vertical plane

How are hair cells oriented in the utricle?

Hair cells polarized to the striola

What determines hair cell activation in the utricle?

Pattern of neuronal activity, not a given head position

What are the otolithic organs responsible for?

Head position | Linear acceleration

How are hair cells oriented in the saccule?

Hair cells polarized AWAY from the striola

What is benign paroxysmal positional vertigo?

Otoconia (Ca carbonate crystals) detach from otolithic membrane of utricle and get stuck in semicicular canal. May disrupt fluid flow and cause vertigo

What is the function of the lateral vestibular nucleus?

control posture and vestibulospinal reflexes

What is the function of the medial and superior vestibular nuclei?

Vestibulo-ocular reflexes | Vestibulo-cervical reflexes

What is the the function of the inferior vestibular nucleus?

Integration of inputs from the vestibular labyrinth and the cerebellum

How do the vestibular system and the cerebellum interact?

Afferents travel Via the flocculonodular lobe to the cerebellum to help with cerebellar control of posture

What is the function of the lateral vestibulospinal tract?

Principal pathway by which otolithic organs can regulate bodies extensor organs

How does the lateral vestibulospinal tract project?

Ipsilaterally

What is the function of the medial vestibulospinal tract?

Determine head position relative to the body

How does the vestibulospinal tract innervate?

Bilaterally

What is a tumor of VIII called?

Schwannoma

What nerves can a Schwannoma compress?

VIII (where it grows) VII V

How is a Schwannoma treated?

Surgical removal

What is nystagmus?

Involuntary rhythmic movement of the eyes - rapid movement in one direction, slow movement in the other

How is nystagmus named?

For the fast component = the opposite side of the damage

What 3 tests can we use to test for nystagmus?

Optokinetic effect Rotation test Caloric Test

How do we visualize optokinetic effects?

Look at lines - fast component is in opposite direction of moving lines

What is the rotation test?

Spin someone around in a chair - if their eyes are moving in the opposite of the direction of the spin, it is nystagmus

What is the caloric test?

Irrigate external auditory meatus with warm or cold water to set up convection currents + displace ampulla.

What is nystagmus with the caloric test?

Toward warm water, away from cold (COWS)

Who does not respond to caloric stimulation? What is this called?

Dysfunctional labyrinth of nerve, canal paresis

What test to use when a patient has canal paresis?

Close eyes, patient drifts to the side of dysfunctional apparatus/nerve

What is gaze nystagmus?

Have patient gaze no more than 30 degrees from front. If there is a problem, nystagmus is CONTRALATERAL to dysfunctional side