Vestibular System Flashcards
hair cell
transducer
-do not fire APs
synapse 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 gravity
series of membranous tubes
-in temporal bone
targets of vestibular info
cortex cerebellum spinal cord -vestibulospinal tract cranial nerve III, IV, VI reticular formation
hair cell anatomy
tallest sterocilia - kinocilium
stereocilia on apical surface
apical vs. basilar hair cell
endolymph - apical
-high K
perilymph - basilar
-low K
baseline activity of hair cell
results in baseline activity of afferent nerve
increase or decrease firing
kinocilium
reference
movement of stereocilia
towards kinocilium - depolarization
away from kinocilium - hyperpolarization
tip links
connect stereocilia
peripheral apparatus
tubes in temporal bone
-nerves through internal acoustic meatus
setup orients and applies mechanical force to hair cell stereocilia
ampulla
ends of semicircular ducts
where hair cells are
otolith organs
where semicircular ducts attach
utricle - semicirc duct attachment
saccule
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 pairs
respond 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 cells
covered by otolith membranes
-membrane has greater mass due to ear stones
striola
division of maculae
-hair cells oppositely polarized in each half
oriented 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 nerve
most 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
cerebellum reticular formation cerebral cortex spinal 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 normal
slow - VOR
fast - visual motor system
named for direction of fast phase
slow nystagmus movement
slow - VOR
vestibulocollic reflex
postural muscles of neck
-extension ipsilateral to depolarized hair cells
bilateral projection
medial vestibulospinal tract
-descending MLF/MVST
vestibulospinal reflex
through lateral vestibulospinal tract
ipsilateral projection
to LMNs in axial and antigravity muscles of limb
vestibular reflexes
based on comparison of differential signals
asymmetry of signals that drives reflexes
lesions
irritative
destructive - more common
hair cells
can be killed with antibiotices
fast phase nystagmus
away from lesion
head/body tilt, leaning and falling toward lesion
