Vestibular Function Flashcards
what are the 3 major functions of the vestibular system
subjective awareness of body position/movement
postural tone and equilibrium
stabilization of eyes in space during head movements
what are the otolith organs
utricle saccule
what are the semicircular canals
anterior, posterior, horizontal
what do otolith organs contain
a macule which contains hair cells
what are teh senosry receptor cells in the vestibular system
hair cells
what happens if stereocilia are bent towards kinocilium
cell depolarizes adn releases additional neurotransmitter
what happens if stereocilia are bent away from kinocilium
hyperpolarizes adn decreass neurotransmitter release
how is the macula of utricle oriented
parallel to ground
how is macula of saccule oriented
vertical to ground when head is upright
how are hair cells in the ampulla/cupula stimulated
by angular acceleration
how do semicircualr canals respond to head turning
horizontal canal receptors on one side increase their firing rate and receptors on the other side decrease firing
vestibulo-ocular reflex
response to head terns
if head is tilted to one side how do the eyes rotate
in opposite direction
what is the function of VOR
help maintain visual field in horizontal plane
what is the slow conjugate movement of the eyes that compensates for head turns driven by
vestibular system
what direction is slow eye movement
away from head turn
what direction is fast eye movement
towards head turn
rotatory nystagmus
slow phase of nystagmus - opposite direction of head turn
fast phase nystagmus
moves eyes back to midline, in direction of head turn
post-rotatory nystagmus
occurs after a person stops turning
caloric test for vestibular function
water test
cold water
fast phase to opposite ear
warm water
fast phase towards same ear
what happens if you do a carloric test in an unconcious pt
they do not have the fast phase
what does doll’eye maneuver test
brainstem function in an uncouscious pt
what do you see in the doll’s eye maneuber
slow phase nystagmus
benign paroxysmal positional vertigo
not caused by intra-crainial neoplasm, but by free floating aprticles
how long does vertigo last in BPPV
40 seconds or less
is there hearing loss in BPPV
no
what causes meniere syndrome
imbalance between production and reabsorption of endolymph
what are the symptoms of meniere syndrome
sensation of ear fullness
tinnitus
severe acute vertigo
where are the vestibular nuclei located
rostral medulla and caudal pons
where do the vestibular nuclei project
MLF
Laterl vestibulospinal tract
medial vestibulospinal tract
high centers
what happens to projection that goes to MLF
vestibulo-ocular reflexes
what happens to projection that goes to lateral vestibulospinal tract
control o fmotor neurons o flimb and trunk for maintence of balance and posture
what happens to projection that goes to medial vestibulospinal tract
control neck muscles/head position
what happens to projection that goes to higher centers
conscious awareness of body orientation and motion
what do utricle and saccula measure
linear acceleration
what happens if your head is tiled back
hair cells bent toward kinocilia - increased firing rate
what happens if you tild head forward
decreased firing rate
what type of firing rate do otolith organs have
tonic
vertigo
feeling that the world is spinning around or that your head/body are spinning
