Term
| Special Somatic Afferent (SSA) |
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Definition
cochlear division= auditory info
vestibular division= positions and movements of the head in space, moves eyes with head or fixes eyes
innervate sensory end organs (cilia)
deafness, dizziness, balance, vertigo, nystagmus |
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Term
| vestibulocochlear structures in temporal bone |
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Definition
| membranous labyrinth suspended in bony labyrinth |
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Term
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Definition
similar to extracellular fluid (low K, high Na)
inside bony labyrinth |
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Term
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Definition
similar to intracellular fluid (high K, low Na)
inside membranous labyrinth |
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Term
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Definition
sensory hairs protrude into endolymphatic spaces and covered with gelatinous cupulas
Receptor potential results from movement of hair in fluid |
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Term
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Definition
| vesitbule and 3 semicircular canals plus 2 otolithic organs: utricle/saccule |
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Term
| ampulla of semicircular canals |
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Definition
dilations at one end of each canal
crista (cone) |
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Term
| Specialized microvilli of crista |
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Definition
stereocilia-
kinocilium- single
endolymph pushes stereocilia towards kinocilium causing depolarization
moving stereocilia away from kinocilium causes re-polarization |
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Term
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Definition
horizontal
anterior- parallel to posterior canal of other side
posterior |
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Term
| Enodlymph movement with head rotation |
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Definition
endolymph lags behind because of inertia deflecting hair cells in ampulla
endolymph catches up and stimulation ceases
endolymph continues to move briefly as rotation stops resulting in hair deflection in opposite direction |
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Term
| Semircular canals respond best to... |
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Definition
| changes in speed of rotation |
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Term
| Utricle and saccule macula |
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Definition
patch of hair cells instead of crista
embedded in gelatinous substance called otoliths or otoconia |
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Term
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Definition
| head tilts from head upright |
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Term
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Definition
| tilts beginning from head sideways |
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Term
| central connections: vestibular ganglion |
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Definition
contains cell bodies of primary afferents
located in internal auditory meatus |
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Term
| Central axons enter brainstem at |
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Definition
pontomedullary junction
-fibers that enterinferior cerebellar peduncle= ipsi
- most fibers go to vestibular nuclei of medulla/pons |
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Term
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Definition
| inferior, superior, medial, lateral |
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Term
| vestibular nuclei recieve inputs from |
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Definition
| spinal cord, cerebellum, contralateral vestibular nuclei |
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Term
| Second order fibers project from vestibular nuclei to |
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Definition
-same cerebellar region as 1st order fibers
LVST=ipsi- postural compensation to tilting of body
MVST=bilateral- stabilizes head position as body moves |
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Term
| second order fibers project from vestibular nuclei to: |
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Definition
thalamus- Bilaterally via lateral lemniscus or reticular formation
to cortex- parietal lobe and superior temporal gyrus
To motor nuclei of extra ocular mm via MLF (medial longitudinal fasciculus) |
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Term
| Vestibuloocular Reflex VOR |
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Definition
gaze remains fixed on object while head is moving
Afferent limb= cranial nerve 8
efferent limb= 3, 4, 6
rotate head left= increase depolarization of left hair cells= excitatory connect with left vestibular nuclei, activation of R abducens and MLF pathway-eyes both deviate R |
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Term
| Vestibulospinal Relfex VSP |
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Definition
stabilizes head and body
includes vestibulocolic relfex and tonia and dynamic labyrinthine reflexes
head tilted to one flexor activity and extensor activity opposite |
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Term
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Definition
| maintain head vertical with respect to gravity |
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Term
| Spinocervical tract (lateral cervical system) |
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Definition
carries info from hair receptors, tactile receptors, and nociceptors
1st order fibers synapse at dorsal horn> 2nd order fibers ascend ipsi to lateral cervical nucleus
axons cross midline in ventral white commisure and join medial lemniscus projections to thalamus
4th order fibers project to somatosensory cortex
compliments dorsal columns |
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Term
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Definition
regulate postural adjustments of body
Medial tract= neck and back motor neurons
lateral tract= neck, back, arm and leg muscles
excites extensor motor neurons and inhibits flexor motor neurons |
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