Vestibular System Flashcards

1
Q

Peripheral Vestibular System

A

-Vestibular Apparatus
-Semicircular Canals
-Otolithic Organs

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2
Q

Central Vestibular System

A

Pathways: vestib ganglion < vestib nuclei
-Medial longitudinal fasciculus
-Vestibulospinal tracts (med/lat)
-Vestibulocolic
-Vestibulothalamocortical
-Vestibulocerebellar
-Vestibulorecticular

Vestibulocerebellum

Vestibulocortex

Vestibib Nuc

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3
Q

Vestibular Apparatus

A

Semicircular Canals: ant, pos, horizontal
-each with an ampulla

Otolithic Organs: utricle, Saccule

Membranous Labyrinth
-separated by perilymph fluid
-filled with endolymph
-hair receptor cells bend with mmt

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4
Q

Semicircular Canals

A

-Ampulla that contains a crista with a cupula (gelatanous structure containing hair)
-hairs constanly fire AP when at rest and with head mmts to give information about the body in space
-only actively move during rotation of head

Horizontal: head rotation (no)
Ant and Post: pitch and roll (yes)

-R and L Posterior and anterior work in same plane

Ex: Turn to the L, L endolymph shifts toward kinocilium (activating), R endolymph shifts away froom kinocilium

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5
Q

Otolith Organs

A

Urtricle and Saccule: membranous sac that responds to linear acceleration/decceleration
-have a macula that contains hair cells embedded in a gelatinous mass with microscopic cristals (otoliths) on top
-displacement of otoliths sttimulate neurons

Uricle: Horizontal mmt
Saccule: vertical mmt

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6
Q

Cervical-Ocular Reflex

A

-postural adjustments of head in response to SCC
-substitution for VOR when absent

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7
Q

Vestibulo-Spinal Reflex

A

-postural tone and adjustments of the body for balance while maintaining equilibrium

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8
Q

Medial Longitudinal Fasciculus

A

-Bilateral connections to extraocular eye muscles and superior colliculus

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9
Q

Cerebello-Thalamocortical Pathways

A

-ascending pathway
-lateral and superior vestib colliculi < thalamus < posterior parietal cortex

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10
Q

Vestibular System Function

A

-provides CNS info of head and body
-stable visiono while head is moving
-internal refernce to determine appropriateness of sensory info

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11
Q

Vestibulo Occular Reflex

A

-head and eyes move in diff direction to maintain view
-opp lateral rectus activate to move eyes in same direction

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12
Q

Activation of hair cells

A

-movement that bends hair toward kinocilium causes depolarization and activation
-movement that bends hair away from kinocilium causes hyperpolarization and deactiviation

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13
Q

Otolith Ocular Reflex

A

-input from otoliths
-output to eye muscles
-controls horizoontal and vertical eye mmts
-via linear VOR

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14
Q

Benign Parooxysmal Positional Vertigo

A

-BPPV
-most common
-crystals from utricle or saccule (MC) fall into SCC (PSCC MC)
-cause change in endolymh viscosity and fire nerve signals
-brief vertigo and nystagmus

Canalithiasis (MC):
-otoconia fall off and free float in PSCC
-latent onset of vertico and nystagmus after provoking
-disappears in 1 min

Cupulolithiasis:
-otoconia fall off and adhere to cupula of PSCC making cupula denser around endolymph
-immediate vertigo is persistent until head moved
-nystagmus

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15
Q

Nystagmus

A

-non voluntary rhythmic oscillation of eyes
-named by fast phase
-can be suppressed by fixation
-viewed with frenzel or infared goggles

CNS:
-smooth pursuit and saccades (cerebellum and brainstem)
-often follows gaze
-typically vertical, constant

Peripheral Vestib:
-Slow phase: VOR
-fast phase: corrective saccade
-usually horizontal

BPPV:
-named by torsion (canal) and rotary component toward lesion
-Upbeat and rotary for PSCC

Physiologic: induced by normal stimuli; spinning
Pathologic: abnormal, 4 types

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16
Q

Neuritis/Labyrinthitis

A

Neuritis: no hearing loss
Labryrinthitis: hearing loss and tinitis

-infection/inflammation causing hypofunction
-fireing rate affected
-long lasting 3-7d
-nystagmus fixed on good side in all 3 degrees of gaze

17
Q

Acoustic Neuroma

A

-tumor on cochlear n

18
Q

Endolymphatic Hydrops/Meniere’s

A

-chroonic condition of inner ear

19
Q

Fistula/Dehiscence

A

-trauma, fluid exchange, tears

20
Q

Vesibular Hypofunction

A

-damage to inner ear or vestib n
-affects VOR and VSR

-unilateral: dizzy
-bilateral: moving images

21
Q

Spontaneous Nystagmus

A

-cns or pns vestib problem

22
Q

Positional Nystagmus

A

-paroxysmal or static
-Torsional: BPPV or brainstem
-Down/upbeat: cerebellar dysfunction

23
Q

Gaze evoked Nystagmus

A

-eyes drift toward center, contantly corrective

24
Q

Congenital Nystagmus

A

-birth