Vestibular System Flashcards
hair cell
transducer-do not fire APssynapse with primary afferents
primary afferents
-axons in vestibulocochlear nerve-cell bodies in vestibular ganglion (petrous portion of temporal bone)don’t decussate
vestibular system
signals posntion and movement-detects acceleration and gravityseries of membranous tubes-in temporal bone
targets of vestibular info
cortexcerebellumspinal cord-vestibulospinal tractcranial nerve III, IV, VIreticular formation
hair cell anatomy
tallest sterocilia - kinociliumstereocilia on apical surface
apical vs. basilar hair cell
endolymph - apical-high Kperilymph - basilar-low K
baseline activity of hair cell
results in baseline activity of afferent nerveincrease or decrease firing
kinocilium
reference
movement of stereocilia
towards kinocilium - depolarizationaway from kinocilium - hyperpolarization
tip links
connect stereocilia
peripheral apparatus
tubes in temporal bone-nerves through internal acoustic meatussetup orients and applies mechanical force to hair cell stereocilia
ampulla
ends of semicircular ductswhere hair cells are
otolith organs
where semicircular ducts attachutricle - semicirc duct attachmentsaccule
angular acceleration
semicircular ducts
linear acceleration
otolth organs
utricle
horizontal acceleration
saccule
vertical acceleration
fluid lags
when head rotation occurs
head rotation
tubes rotate-endolymph lags behind-this is detected by hair cells in ampulla
functional pairs
semicircular ducts function in right/left pairsrespond oppositely in response to head turn-gives differential signal
differential signal
important because it increases sensitivity of the system-detect minute accelerations
otolith organs
sense linear acceleration/gravity
utricle
horizontal
saccule
vertical
maculae
in utricle and saccule-has hair cellscovered by otolith membranes-membrane has greater mass due to ear stones
striola
division of maculae-hair cells oppositely polarized in each halforiented in curve
each maculae
gives differential signal
maculae orientation
every plane in x and y axis
peripheral apparatus
include semicircular ducts and otolith organs-detect acceleration and gravity
primary efferents
cell bodies in vestibular ganglion
axons of primary efferents
vestibulocochlear nervemost synapse in vestibular nuclei-some to cerebellum (ipsilateral)
vestibular nuclei
four each side-ventral and lateral to 4th ventricle-distribute info and regulate reflexes
vestibular nuclei activity
have baseline
targets of vestibular information
cerebellumreticular formationcerebral cortexspinal cortex (LVST/MVST)cranial nerve III, VI, VI-eye movement opposite to keep image on retina
vestibuloocular reflex
moving head allows you to focus on moving words-maintain gaze during head movements
path of vestibuloocular reflex
axons in MLF - ascend to motor nuclei of III, IV, VI
abducent nuclei
cell bodies that are LMNs-ipsilateral lateral rectus m.
trochlear nuclei
superior oblique m.
oculomotor nuclei
medial rectus, and others
nystagmus
series of back and forth eye movements-slow one way, fast other way-can be pathologic of normalslow - VORfast - visual motor systemnamed for direction of fast phase
slow nystagmus movement
slow - VOR
vestibulocollic reflex
postural muscles of neck-extension ipsilateral to depolarized hair cellsbilateral projectionmedial vestibulospinal tract-descending MLF/MVST
vestibulospinal reflex
through lateral vestibulospinal tractipsilateral projectionto LMNs in axial and antigravity muscles of limb
vestibular reflexes
based on comparison of differential signalsasymmetry of signals that drives reflexes
lesions
irritativedestructive - more common
hair cells
can be killed with antibiotices
fast phase nystagmus
away from lesionhead/body tilt, leaning and falling toward lesion
