Eye Movements Flashcards
The four rectus muscles:
Originate from:
Insert ______ on the sclera
The two oblique muslces
SO originates from:
IO originates from
both inserts ______ on the sclera
Four rectus muslces:
originate from a common tendinous ring (annulus of Zinn)
insert anteriorly in the sclera
The rectus muscles:
Superior oblique originates from the sphenoid bone (back of orbit)
Inferior oblique originates from the front medial floor of the orbit
both insert posteriorly in the sclera
What type of motor unites are used by the ocular muscles?
unusually small, composed of fatigue-resistant type 2A fibers
PPRF lesion –>
The side of the lesion corresponds to the ____ side of failure of lateral gaze
MLF lesion –>
The side of the lesion correspondes to the ___ side of failure to adduct on lateral gaze
PPRF –> GAZE palsy
side of lesion = side of failure to conduct lateral gaze
(ie- lesion on left, eyes can’t move to the left = gaze palsy; eyes can both move to the right)
MLF lesion –> internuclear opthalmoplegia
Side of lesion corresponds to the side of the eye that fails to adduct on lateral gaze
Centers for Conjugate Gaze:
@brainstem:
Rostral Interstitial Nucleus —> _____ gaze center
PPRF —> ______ gaze center
@ Cortex
Frontal Eye Field –> ____ an object on the fovea
Fxn:
Occipital Eye Field –> ____ an object on the fovea
Fxn:
Rostral Interstitial Nucleus = VERTICLE gaze center
PPRF = HORIZONTAL gaze center
Frontal Eye Field: BRINGS an object onto the fovera
FXN: initiates saccadic eye movements
(Frontal = FIND…eye moves rapidly to find the object/focus image on the fovea)
Occipital Eye Field: KEEPS an object on the fovea
FXN: necessary for smooth pursuit
(Occipital = ON the object, smooth tracking of the object)
What is Slow/Pursuit eye movements?
What FOUR movements are involved with SLOW/PURSUIT?
=slow eye movements that keeps images on the fovea (~100 degrees/s), allows for continuous feedback from vestibular and visual systems to regulate speed/duration
- Smooth Pursuit Movements
- Vestibuloocular Reflex
- Vergence Movements
- Optokinetic Movements
Smooth Pursuit Movements:
_____ feedback keeps images of ____ targets on the fovea
Originates in the _____ cortex and uniquely requires _____/______ for its generation
VISUAL feedback keeps images of MOVING targes on the fovea
Volitional, orginates in the EXTRASTRIATE cortex and uniquely requires CEREBLLUM/FLOCCULUS for its generation
Vestibuloocular Reflex:
Generates compensatory eye movements in _____ direction from head movements. Stabilizes the image on the retina during a _____ of the head and faster than visual tracking. As the _____ rotates, the VOR rotates the ______ in the ___ speed and in _____ direction.
“stabilization” occurs through the nucleus __________.
Relies on ______ input
[True/False]Can be suppressed to allow head and eye movemements to shift gaze
Tested with ________ maneuver.
Vestibuloocular reflex = GAZE STABILIZATION
Generates compensatory eye movements in the OPPOSITE directom from head movements. Stabilizes the image of the retina during a rotation of the head and faster than visual tracking. As the HEAD rotates, the VOR rotates the EYES in the SAME speed but in OPPOSITE direction
Stabilization occurs through the nucleus PREPOSITUS HYPOGLOSSI
Relies on VESTIBULAR input
TRUE: CAN be suppressed to allow head/eye movements to shift gaze
Tested with the DOLLS EYE maneuver
Vergence movements
_______ signals are used to guide vergence eye movements of CN ____ and _____ eye musle.
ACCOMODATION signals are used to guide vergence eye movements.
CN III and Medial Rectus muslces
cerebellum involved but not essential for movements
Vestibuloocular Reflex…..
Head is rotating to the RIGHT….____horizontal canal is activated
_____ vestibular nucleus is activates
the _____ 6th nucleus via _____ is activated and the ____lateral rectus muscle contracts
the left PPRF activates neurons in the _____ 3rd nucleus and the _____ medial rectus contracts
–> BOTH eyes begin to move to the LEFT
Head is rotating to the RIGHT….right horizontal canal is activated
right vestibular nucleus is activated
the right 6th nucleus via PPRF is activated and the left lateral rectus muscle contracts
the left PPRF activates neurons in the right 3rd nucleus and the right medial rectus contracts
–> BOTH eyes begin to move to the LEFT & object of interest stays on the fovea
Saccadic eye movements are ____ eye movements that:
Initiated from teh _________ eye fields, using the _______ gyrus
Used in reading, scanning scenes and pictures, etc
During this time, images are _____ (clear/blurred)
Rapid horizonatal eye movements are generates from the ____
Rapid vertical eye movements are generated from the ____
Saccadic eye movements are FAST EYE MOVEMENTS that MOVE an IMAGE onto the FOVEA (~700 degrees/s)
During this time, images are blurred
Rapid horizontal eye movements are generated from the PPRF (paramedian pontine recticular formation )
Rapid vertical eye movemetns are generated from the reticular formation dorsomedial to the red nucleus (riMLF)
How can you confirm when an eye doesn’t adduct, it is due to a MLF lesion rather than a problem with the medial rectus?
test CONVERGENCE
In a MLF lesion, both eyes can move in (adduct) = converge, thus you can confirm that the medial rectus of hte eye that does adduct on lateral gaze is functional
How? convergence invovled the anterior portion of the MLF so it bypasses the lesion in the inferior portion of the MLF where it is disrupted
