Eye Movements Flashcards
What is the representation of the optic disk in the visual field?
the blind spot
This is moving the fovea to an object closer (convergence) or farther away (divergence).
vergence
What signals the rotation of the head?
the semicircular canals
Saccades can be voluntarily generated by the _____.
frontal eye field (FEF)
The oculomotor system is subject to modulation by the ____ and ____.
cerebellum; basal ganglia
What is inhibited during conjugate gaze?
antagonist motor neurons
When is nystagmus normal?
when the head is rotated for along time or when there is a moving visual stimulus
What initiate conjugate eye movements?
a variety of sensory inputs, especial visual and vestibular
What are the 2 important control centers for saccades?
- the cortex
- the superior colliculus
If the head turns to the right, the eyes ____.
counter rotate to the L
Smooth pursuit can only maintain foveation at a rate of about _____.
50 degrees/second
The direction of the nystagmus is defined by _____.
the direction of the rapid saccade
What are saccades?
rapid, ballistic eye movements (to bring an object onto the fovea)
Where is the pattern generator for horizontal saccades?
in the reticular formation near the abducens nucleus (the paramedian pontine reticular formation- PPRF)
What eye condition do MS patients often get?
internuclear ophthalmoplegia (INO)
Cells in the vestibular nuclei project by way of the ______ to excite lateral rectus motor neurons in the abducens nucleus.
medial longitudinal fasciculus (MLF)
Saccades can be reflexively directed from the _____.
parietal eye field (PEF)
If the frontal eye field is damaged, the is a _____.
temporary loss of the ability to generate saccades
Interruption of the _____ can cause discoordination of medial and lateral recti muscles during horizontal gaze movements, called internuclear ophthalmoplegia (INO).
medial longitudinal fasciculus (MLF)
Coordinate contraction of the 2 eyes is accomplished by _____ that reside in the vicinity of the oculomotor and abducens nuclei.
interneuronal pattern generators
What is an example of a vergence movement?
when both eyes turn towards the nose for near reading
Horizontal saccades are driven ____.
contralaterally
What are the vestibular ocular reflex (VOR) and optokinetic nystagmus (OKN) eye movements?
a combination of pursuit and saccades
What is the frontal eye field?
an area near the motor cortex that activates saccades via the reticular formation and/or the superior colliculus
Who often gets internuclear ophthalmoplegia (INO)?
MS patients
What is vergence?
moving the fovea to an object closer (convergence) or farther away (divergence)
Interruption of the medial longitudinal fasciculus (MLF) can cause ______, called internuclear ophthalmoplegia (INO).
discoordination of medial and lateral recti muscles during horizontal gaze movements
What are microsaccades?
the eye moving in small jumps to refresh the image several times/sec so it is never stabilized
The medial longitudinal fasciculus (MLF) is especially vulnerable to interruption bc of _____.
its length
Movement brings the fovea to an area that was being analyzed by _____.
that side of the brain
More complex eye movements are programmed in specialized regions of ____.
the neocortex
What muscles are responsible for horizontal rotation?
the lateral and medial rectus
What CN innervates the lateral rectus?
CN6
If the superior colliculus is damaged, ______.
saccades are less accurate and occur less often
If the head continues to turn, the eyes rotate slowly until the limit of eye rotation is reached, then they _____.
snap quickly back to a new fixation point
What are vergence movements?
eye movements in opposite directions
What happens physiologically during the near/accommodation reflex?
- contraction of the medial recti
- pupil constriction
- ciliary muscle constriction
What are conjugate movements?
when both eyes move in the same direction
Interruption of the medial longitudinal fasciculus (MLF) can cause discoordination of medial and lateral recti muscles during horizontal gaze movements, called ______.
internuclear ophthalmoplegia (INO)
For stimuli moving faster than 50 degrees/second, a combination of _____ and ____ is used.
saccades and smooth pursuit
Where is the blind spot located in the visual field?
15 degrees lateral
These are rapid, ballistic eye movements (to bring an object onto the fovea).
saccades
Where is the pattern generator for vertical saccades?
near the oculomotor nuclei
Any stimuli that excites the abdences also excites the ____.
internuclear interneurons
What are the 4 types of eye movements?
- smooth pursuit
- saccades
- vestibular ocular reflex (VOR) and optokinetic nystagmus (OKN)
- vergence
When is nystagmus abnormal?
due to damage of the vestibular system or cerebellum
What CN innervates the medial rectus?
CN3
This is tracking to keep an object on the fovea.
smooth pursuit
If BOTH the frontal eye field and the superior colliculus are damaged, _____.
there is a permanent loss of the ability to make saccades
The eye moves in small jumps called _____.
microsaccades
Voluntary eye movements are driven by the _____.
frontal lobes
These eye movements are a combination of pursuit and saccades.
the vestibular ocular reflex (VOR) and optokinetic nystagmus (OKN)
What do saccadic eye movements activate via the superior colliculus?
the brainstem gaze center (BGC)
During conjugate gaze to the left, the left lateral rectus and the right medial rectus muscles are _____ and the left medial rectus and right lateral rectus are ______.
activated; inhibited
What is smooth pursuit?
tracking to keep an object on the fovea
