Vestibular system Flashcards
hair cells
mechanoreceptors in the ampula of semicircular canals
synapse on primary afferents in the vestibulocochlear n.
where cell bodies in the vestibular ganglia
baseline activity of hair cells
releases a set amt of NT at rest
sets baseline activity of primary afferent, can be adjusted to increase or decrease
movement of sterocilia
all in reference to kinocilium
movement towards kinocilium —>stretches tiplinks—>opens K channels—>depol
movement away—> tiplinks close—>closes K+ channels—>hyperpolarization
tiplinks connect sterocilia
peripheral vestibular apparatus
set of membranous tubes house in bone
this setup orients and supplies a mechanical force to hair cell stereocilia
**applies force to hair cells so that we can detect things in all directions
semicircular ducts
contain hair cells within ampulla
detect fluid lag when head rotation occurs
detect angular acceleration in ANY plane
Otolith organs
detect linear/gravity orientation
Utricle- in X
Saccule- in Y
Maculae are located in both areas and are the actual sensory structures
contain otoliths (Ca carbonate) that lag behind to pull on gel and hair cells
Crista and Cupula
part of semicircular ducts at the ampulla
hair cells in crista
sterocilia in the cupula (gel-like)
KINOCILIUM CLOSEST TO UTRICLE
functional pairs
R and L pairs of sterocilia respond oppositely
give a differential signal. Ex:
Turn to left, L SC depolarize and R SC hyperpolarize in equal and opposite direction
Ø CNS measures difference to determine direction and speed of rotation
Ø GREATLY INCREASES SENSITIVITY OF THE SYSTEM
Striola
line that divides maculae in half
hair cells have opposite orientation on either side
each macula gives off a differential signal
maculae
hair cells oppositely polarized in each half
each macula give differential signal
House hair cells
primary afferents
cell bodies in the vestibular ganglion
axons from vestibulocochlear n.
most synapse on vestibular nuclei while others synapse directly on ipsilateral cerebellum
targets of vestibular info
cerebellum
RF
CX (via thalamus, VPL)
Spinal cord (LVST and MVST- to postural mm.)
Cranial Nuc III, IV, VI to turn eyes
Vestibuloocular reflex
VOR function to maintain gaze during head movements
keeps the object on the retina as your head moves
vestibular nuclei axons in MLF influence cranial nuclei with motor input to III, IV, VI to influence EOMs
Nystagmus
back and forth eye movement
-slow in one direction, fast in another
slowly controlled by VOR so that you maintain gaze
when eyes cant turn any more, they snap back and reset
named for direction of fast phase (ex Left beating nystagmus when you move your head left)
Vestibulocollic reflex
mediated thru MVST
bl projections in MLF
targets LMNs that innervate neck and thoracic limb muscles
extension ipsilateral to depolarized hair cells
ex with left angular rotation, there is a shift in body weight to the left, so to counteract that, MVST fibers induce extension of Left neck mm.
