4 - Eye Movements Flashcards
lateral wall is _ degrees from sagittal plane, and axis of orbit is _ degrees laterally from axis of globe
45, 23
secondary movement of superior rectus:
intorsion
secondary movement of inferior rectus:
extorsion
to isolate movement of superior and inferior rectus, eye must be 23 degrees _
abducted
secondary movement of inferior oblique:
elevation
when eye is adducted, SO _
depresses eye
when eye is abducted, SO _
intorts eye
_ portion of CN III innervate 4/6 EOMs and levator
somatic efferent
_ portion of CN III innervates parasympathetic pupil and ciliary body
visceral efferent
oculomotor nuclear complex lies in _
tegmentum of midbrain
LMNs leave oculomotor nuclear complex and enter orbit via:
superior division to _ _
inferior division to _ _ _ _
SR, levator
IR, IO, MR, parasympathetic fibers
trochlear nerve is longest and most susceptible to damage
somatic efferent to innervates _
nucleus is found in midbrain at level of _
superior oblique
inferior colliculus
two components of abducens nerve:
somatic efferent: innervates _
interneurons: _
LR
relay center for coordination of eye movements, medial longitudinal fasciculus
abducens nucleus in pons leaves and courses over _
petrous ridge of temporal bone
SR is controlled _ by CN III
contralaterally
SO is controlled _ by CN VI
contralaterally
MR is controlled _ by III, and _ by interneurons of IV
ipsilaterally, contralaterally
MLF interconnects which 4 neurons?
3 4 6 8
MLF originates from _
vestibular nuclei of CN VIII
MLF
descending component: _
ascending component: _
vestibulospinal tract
coordination of eye movements
MLF mediates eye movements in response to vestibular stimuli, aka _
Vestibular-Optic Reflex (VOR)
MLF is heavily _
myelinated
horizontal gaze center is _
paramedian pontine reticular formation (PPRF)
vertical gaze center is _
midbrain, reticular formation, and pretectal area
horizontal gaze final common pathway:
ipsilateral PPRF -> ipsilateral _ nucleus -> ipsilateral LR & interneurons in MLF to contralateral III and MR
abducens
PPRF:horizontal gaze::_:vertical gaze
rostral interstitial nucleus of MLF & interstitial nucleus of Cajal & pretectal area
_ portions mediate downgaze, and _ portions mediate upgaze
anterior; posterior
FEF and visual association areas project to vertical gaze centers via _
superior colliculus
from vertical gaze centers, signal travels _ to CN III and IV
bilaterally
visual system is _ during saccadic eye movement
suppressed
cortical areas (lobes) involved in saccades: _ _
parietal (visual association) and frontal (FEF)
reflexive saccades are _ guided in response to external visual cues
visually
volitional saccades are _ of visual stimulus and more complex
independent
looking away from something, saying “I’m not going to look”
antisaccades
look towards where you remember something was
memory saccades
baseball moves too fast, predict where its going to be
predictive saccades
the superior colliculus is a layered structure
superficial layers receive input from _
deep layers have motor neurons that project to _ to initiate saccades
LGN
PPRF
3 saccadic neurons
pause, burst, tonic
pause neurons _ burst cells, engage saccade by _
constantly inhibit; releasing inhibition
burst cells produce _ and control _
brief pulse of innervation; velocity
burst cells are followed by tonic cells that provide _
constant step of innervation and holds it in place
_ cells control final position of eye
tonic cells
with saccades,
agonist is _
antagonist is _
excitatory
inhibitory
combination of pulse and step results in smooth movements with saccades; normal saccade has a gain of _
0.92
typical latency of a saccade is _ ms, shorter if predicatble
180-200
hypometric saccade is when eye doesn’t move far enough; _ is too low
pulse/burst
slow saccade occurs when _ takes a long time
pulse
gaze evoked saccade occurs when _ fizzle out
tonic
pursuits do not orient eyes toward a target, they _
keep the target on the fovea
smooth pursuits is integration of _ _ _ _ _
cortical information, cerebellar, vestibular, CN VI and III
smooth pursuit is only possible with _
slow moving objects
both sides of the cortex are active at the same time in order to _
keep objects centered on fovea
when you think smooth pursuit, contralateral or ipsilateral?
ipsilateral
2 phases of pursuits:
open loop - gets eye moving
closed loop - eye responds to alterations in retinal image produced by eye movements (adjusts velocity)
latency of pursuit initiation is _ ms
130 (much faster than saccade)
saccades are all about: _
pursuits are all about: _
position
velocity
anterior canal moves eyes: _
posterior canal moves eyes: _
horizontal canal moves eyes: _
upward
downward
laterally
_ reflex adjusts head movements so that gaze can remain fixed on object even though head is moving
vestibuloocular reflex
nystagmus is named for direction of _
fast phase
vestibular nystagmus is activated by _
rotation of head -> VOR
optokinetic nystagmus is elicited by _
visual stimuli
following phone poles is an example of _
optokinetic nystagmus
caloric testing mneumonic is _
COWS (cold opposite, warm same)
