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10 Cards in this Set
- Front
- Back
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Endolymph production |
Stria vascularis (pumps -> Δ [ion]) in cochlea -> resorbed via endolymph duct -> sac -> sigmoid sinus |
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Vestibular hair cells: mechanoelectrical transduction |
Endolymph: +80mV; Hair cell: -45mV; Δ: -125mV +/- Movement: hairs (stereocilia) -> kinocilium => pulls tip links => K channels open => K flow: endolymph -> hair cell => depolarizes => VGCC's in base open -> Ca influx -> -- NT release -- Ca-gated K channels open => K flow -> perilymph => repolarization |
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Adaptation & Tuning of Vestibular Hair Cells |
Tip filament - linked to motor protein - linked to Actin filaments (in core of adjacent stereocilium) - ↓ IC [Ca] => motor protein moves upwards => prolonged inaction -> ↑ sensitivity (new baseline; steady NT release) |
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Receptive organs |
Cristae - w/in ampulla of semicircular ducts - all hair cells in 1 direction Maculae - w/in saccule & utricle - small patches of hair cells w/ varying complex, curved 3D orientation, striola down the middle |
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Macula |
- hair cells attached to the wall embedded in gel w/ calcium carbonate crystals (otoliths) -> ↑ density => response to gravity - hair cells depolarized based on location (striola) - detects linear acceleration / position |
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Cristae |
- hair cells protruding into a gelatinous mass (cupula) w/o crystals -> ↓ density -> does not deflect due to gravity - currents w/in endolymph -> deflect cupula => hair cells bend (all simultaneously) -> activate - detect angular acceleration w/in the plane - complementary canals fire in opposite manner |
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Innervation |
Maculae & cristae -> vestibular (Scarpa's) ganglion -> CN VIII -> internal acoustic meatus -> (interconnected:) -- vestibular trigone (medulla/pons): vestibular nuclei (cristae -> L, M, S) -- flocculonodular lobe (vestibulocerebellum) -> MLF (medial longitudinal fasciculus) ->> CN III, CN IV nuclei (vestibulo-ocular reflex, VOR) -> M & L VST (vestibulospinal tracts) (vestibular righting reflex) -> thalamus (VP nucleus complex) -> vestibular cortex (vertigo) |
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Vestibular complex input |
= vestibular nuclei <- vestibular n., part of CN VIII <- vestibulocerebellum: flocculus & fastigial nucleus (Δ VOR gain, vestibular response adaptation) <- spinal cord (proprioception) |
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Vestibulo-ocular reflex (VOR) |
= eye movement compensating for horizontal head rotation CN VIII -> medial vestibular nucleus -> oculomotor nucleus -> medial rectus m. -> abducens nucleus -> lateral rectus m. |
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Nystagmus |
= rapid jerk movement counter to VOR once fixed object is out of sight - also occurs when semicircular canals are being stimulated while the head is not in motion - pathology: occurs when one inner ear / vestibular nerve is damaged -> input imbalance |
