5.8 Vestibular

Question 1

quick step changes in eye position as the visual field is scanned, up to 400-700 degrees/second

Answer 1

saccades

Question 2

during saccades there is no blurring of visual field because _______ is too fast for neurons to respond, and the ________ is inhibited (corollary discharge)

Answer 2

velocity, lateral geniculate nucleus

Question 3

neural path for what type of saccades?
frontal eye field (area 8) –> superior colliculus –> reticular formation –> oculomotor nuclei –> eye muscle –> saccade

Answer 3

neural pathway for voluntary saccades

Question 4

neural path for what type of saccades?
novel stimuluts –> retinal ganglion cells –> superior colliculus –> reticular formation –> oculomator nuclei –> eye muscle –> reflex saccade

Answer 4

reflex/triggered saccades

Question 5

tracking movements, up to 30 degrees/second

Answer 5

smooth pursuit

Question 6

neural path for what type of eye movement?
retinal slip of image on retina –> retinal ganglion cells –> lateral geniculate nucleus –> visual cortex –> reticular formation –> oculomotor neurons -> eye muscles –> movement

Answer 6

smooth pursuit

Question 7

maintain fixation in presence of head movement, up to 300 degrees per second

Answer 7

vetibulo-ocular reflex (VOR)

Question 8

adequate stimulus for kinetic labyrinth (semicircular canals)?

Answer 8

dynamic stimuli (rotational forces) or head acceleration/deceleration

Question 9

adequate stimuli for static labyrinth (otolith organs, utricle, saccule)?

Answer 9

static stimuli, maintained head position (tilit); transitional forces, horizontal displacement

Question 10

viscous fluid filling the canals and otolith organs, continuous with utricle through the canal

Answer 10

endolymph

Question 11

enlargement at one end of a semicircular canal, within it are vestibular hair cell receptors

Answer 11

ampulla

Question 12

gelatinous mass into which the cilia of the hair cells insert

Answer 12

cupulla

Question 13

hair cells synapse with the terminals of _____ axons from CN 8, cell bodies form _______ ganglion

Answer 13

afferent, Scarpa’s

Question 14

simple long cilium

Answer 14

kinocilium

Question 15

multiple smaller cilia

Answer 15

stereocilia

Question 16

bending cilia toward the ________ produces _______ of the hair cell and an increase in firing rate of 8th nerve afferent

Answer 16

kinoclium, depolarization

Question 17

bending cilia away from the _______ produces _________ of the hair cell and a decrease in firing rate of the 8th nerve afferent

Answer 17

kinocilium, hyperpolarization

Question 18

adequate stimulus for semicircular canal receptors is ________

Answer 18

head rotation

Question 19

due to inertia, endolymph will tend to move in the direction ______ rotation

Answer 19

opposite

Question 20

subject is rotated in a chair, chair is stopped and vestibular function is examined by observing VOR and vestibulopostural reflexes, effects of deceleration are examined

Answer 20

barany chair test

Question 21

acceleration to the right (rotational phase) would _______ in right 8th nerve activity, and ______ in left 8th nerve activity

Answer 21

increase, decrease

Question 22

rotation at constant angular velocity has no effect after about 30 seconds because endolymph has _________

Answer 22

equilibrated

Question 23

deceleration (post rotational phase) has _______ in right 8th nerve activity and _______ in left 8th nerve activity

Answer 23

decrease, increase

Question 24

involuntary back and forth, up and down, or rotating movement of eyeballs, with a slow pull and rapid return jerk

Answer 24

nystagmus

Question 25

a lesion will cause subject to fall ______ side of lesion and have nystagmus on _______ side

Answer 25

toward, opposite

Question 26

in right rotational phase, increase in CN8 actiivty –> activation of right (flexors or extensors?) and decreased CN8 activity on the left inhibits left _______ –> will fall to the _______

Answer 26

extensors, extensors (flexion), left

Question 27

in right post-rotational (deceleration) phase, decreased CN8 activity leads to inhibition of right _____, and increased CN8 activity on the left leads to _________, therefore patient will fall to _______

Answer 27

extensors (flexion) , extension, right

Question 28

caloric stimulation test: irrigation with warm water causes ________ nystagmus, irrigation with cold water causes _______ nystagmus

Answer 28

same side, opposite, (COWS)

Question 29

in unilateral lesions of CN VIII, the patient falls (toward or away?) side of lesion, and get nystagmus to (same or opposite side?)

Answer 29

toward lesion, opposite nystagmus