Flashcards in W21-L9: Control of Eye movements Deck (16):
What are the two systems that stabilize an image of an object on the retina?
Oculomotor and Head-movement system
What is the Oculomotor system?
Moves the eyes in the orbit (whilst head is still)`
Involves extraocular muscles and neural pathways that coordinate movement of each eye.
What is the Head-movement system?
moves the eye sockets as a whole (whilst head moves).
Involves vestibular system as well as oculomotor system
Primary actions of recti
Superior Rectus: Elevation
Inferior Rectus: Depression
Medial rectus: Adduction
Lateral rectus: abduction
What is the function of Superior Oblique?
torsion (rotation), adduction and depression
What is the function of Inferior Oblique?
torsion, adduction and elevation
Why do muscles have multiple actions?
mulitple actions of the muscles on the eyeballs is due to the angle of insertion
What is the Medial longitudinal fasciculus?
White matter tract that connects the various cranial nerve nuclei
What is the Pontine paramedian reticular formation?
-Horizontal gaze centre
-coordination of MR and
LR of each eye
-coordination of CNIII & CNVI
What is the Mesencephalic paramedian reticular formation?
-Vertical gaze centre
-Coordination of SO and SR of each eye
-Coordination of CNIV and CNIII
What are the two types of neurones in the Pontine Paramedian reticular formation?
Burst neurones (drive contraction) which fire just before movement and omnipause neurones (inhibit contraction) which work all the time when not contracting
What is the neural control of saccades?
1. Excitatory burst neurones receive input from the cortex
2. Stimulates ipsilateral LR via abducens nucleus
3. Via MLF stimulates contralateral CN III nucleus and contralateral MR
4. Inhibitory burst neurones inhibit contralateral abducens via MLF which inhibits contralateral LR
5. Also via MLF ipsilateral CN III nucleus and MR are inhibited
Where do frontal eye fields control saccades?
controls saccades in the contralateral direction
What do Semicircular canals signal?
What does otolith signal?