Eye Movements 1 & 2 Flashcards
The eye moves in small jumps called ______ to refresh the visual image several times per second so that it is never stabilized.
“microsaccades”
Once an object of interest is on or near the fovea, we use slower movements, ______, to track a moving object
pursuit
a rhythmic pattern of saccades and tracking movements is called _________
“optokinetic nystagmus”
describe vestibular nystagmus
a sawtooth movement of the eyes, slow ramp opposite to head rotation, fast saccade to center of eye position,
the direction of nystagmus is defined by the direction of the _______
rapid saccade
Our eyes make ______ movements (with both eyes moving in the same direction)
conjugate
we can make ________ movements (eyes moving in opposite directions, e.g., when both eyes turn nasally)
vergence
describe the actions that occur during a near (accommodation) reflex.
Both medial recti contract, pulling the eyes nasally. The pupils constrict to increase the depth of field. The ciliary muscles contract, allowing the lens to become fatter and thus focus on a near object
damage to the medial longitudinal fasciculus (MLF) can disconnect the coordination of medial and lateral recti during horizontal gaze movements. This condition is called ________.
internuclear ophthalmoplegia (INO)
The oculomotor (III) nuclei contain motoneurons for the \_\_\_\_\_\_\_\_\_.
medial rectus, inferior and superior recti and inferior oblique muscles.
The trochlear (IV) nucleus contains motoneurons innervating the _______ muscle
superior oblique
The abducens (VI) nucleus provides motoneurons for the _______ muscle
lateral rectus
the lateral and medial recti are responsible for _____ .
horizontal rotation
the superior rectus and inferior rectus are largely responsible for __________(with slight rotation about the visual axis as well).
vertical displacements
what is caloric nystagmus.
a nystagmic pattern of eye movements that is independent of visual input, and elicited by a highly unusual pattern of vestibular input
describe optokinetic nystagmus” (OKN or OPK)
similar in appearance to vestibular nystagmus.
A simple visual stimulus like a rotating striped drum elicits the response well (more commonly experienced as one watches the passing scene, such as telephone poles, from a moving vehicle).
The frontal eye field can activate saccades by two pathways, one direct to the ________ and one via the ________- to the reticular formation
reticular formation,
superior colliculus
If both the frontal eye field and the superior colliculus are damaged, there is _________ of the ability to make saccades.
permanent loss
Saccades can be reflexively directed from the ________ or voluntarily generated by the ______. These activate the Brainstem Gaze Center (BGC) directly or indirectly through the superior colliculus (SC)
parietal eye field (PEF),
frontal Eye Field (FEF)
If the _______ is damaged, saccades are less accurate and occur less often but still happen.
superior colliculus
If the _________ is damaged, there is a temporary loss of the ability to generate saccades.
frontal eye field
during a VOR, Rightward head rotation is signaled by horizontal canals, leftward eye rotation is produced by excitation of motor neurons to the left ______ in left abducens nucleus, and excitation of right _____ by motor neurons in right oculomotor nucleus.
lateral rectus,
medial rectus
Cells in the vestibular nuclei project by way of the _________ to excite left lateral rectus motor neurons in the abducens nucleus
medial longitudinal fasciculus (MLF)
