4.19 Vestibular 3 Flashcards
What are the 2 eye reflexes we talked about for gaze stabilization?
- vestibulo-ocular reflex (VOR)
- optokinetic reflex
What is gaze stabilization
visual fixation: keeping gaze steady during head movements
What does the VOR do?
- stabilizes visual field during fast head movements
- moves the eyes in the opposite direction to the head
VOR: voluntary or automatic?
automatic
frontal control and VOR
frontal control required to suppress the VOR and move eyes with the head
What happens to the eyes when you move the head quickly
they lag behind
What type of reflex is the VOR considered?
brainstem reflex
VOR is needed to be able to do this
look L & R back and forth (as well as up/down)
Why does nystagmus occur? (VOR)
- excessive VOR stimulation
- pathological damage
VOR can’t keep up with head rotation
VOR normally does this for rotation
compensates for rotation
How can the VOR be triggered normally?
- excessive rotation
- quickly moving objects
What is pathologic nystagmus?
nystagmus with NO excessive rotation
Where is the damage with pathologic nystagmus?
in the semicircular canals or the receptors for the canals
could also be in the vestibulocerebellum or due to a problem with the otoliths
Both the optokinetic and the VOR go through this nucleus
medial vestibular nucleus
function of optokinetic reflex
- stabilizes images during slow head movements
- helps focus on larger objects int he visual field
