Exam 2 - vestibular system Flashcards
vestibular disease
nystagmus w/ fast phase away from side with lesion (post-rotary is normal)
head tilt toward side of lesion
leaning/circling toward side of lesion
strabismus - both eyes and usually ventral or ventrolateral deviation ipsilateral to lesion when nose elevated
paradoxical vestibular disease
associated w/ lesions of flocculonodular lobe or cerebral peduncles = signs are contralateral to lesion
nystagmus w/ fast phase towards lesion
head tilt away from lesion
circling/leaning away from lesion
how do you diagnose paradoxical vestibular disease
deficits of conscious perception will be ipsilateral to lesion
deficits of voluntary movement will be ipsilateral to lesion
signs of cerebellar dysfunction (ataxia) will be ipsilateral to lesion
peripheral conditions of vestibular system
normal proprioception
normal strength/voluntary motor
horizontal/rotary nystagmus
nystagmus doesn’t change when the head position changed “constant”
includes vestibular apparatus in inner ear and/or vestibular division of vestibular cochlear n.
central conditions of vestibular system
paresis
loss of proprioception
horizontal, rotary, vertical nystagmus
nystagmus changes with head position “positional nystagmus”
affects vestibular nuclei in pons and/or medulla
vestibular system
stable orientation in relation to gravity and movement
orientation of eyes, neck, trunk limbs in reference to movement or position of head
bony labyrinth is full of _____
perilymph
membranous labyrinth is full of ____
endolymph
vestibular apparatus made up of _____
utriculus
sacculus
semicircular ducts
maculae
neuroepithelium of utriculus and sacculus
detects linear/gravitational acceleration
utricle macula
horizontal
saccular macula
vertical
hair cells composed of _____
stereocilia (many)
kinocilium (one)
the stimulus of hair cells
bending of cilia towards or away from kinocilium
towards = depolarization
away = hyperpolarization
hair cells of vestibular system acceleration/vibrations
hair cells of cochlear system acceleration/vibrations
acceleration
vibrations
semicircular ducts
part of membranous labyrinth
filled with endolymph, surrounded by perilymph
detects angular/rotational acceleration
crista ampullaris
neuroepithelium of semicircular ducts
increased activity of the hair cell
cupula go toward ______
stereocilia bend toward _____
utriculus
kinocilium
hyperpolarization
cupula ____
stereocilia _____
buldges away from utriculus
bend away from kinocilium
vestibuloocular reflex
focused retinal image when head moves
movement of eyes in opposite direct of head
nystagmus
medial longitudinal fasciculus (MLF)
vestibulocolic reflex
descending portion of MLF = medial vestibulospinal tract
neck movement and forelimb extension that counteract tilt of head
increases extension of ipsilateral neck and forelimb to side of acceleration
vestibulospinal reflex
lateral vestibulopsinal tract
limb extension that counteracts the displacement of the head that elicits it
extension of ipsilateral forelimb and hindlimb, inhibits ipsilateral flexors and inhibits contralateral extensors
Vestibular reflexes are based on a ______________ of the signals coming from left & right vestibular apparatus; it is the _______________ between the two sides which __________
comparison
asymmetry of firing
drives the reflexes
