Final 4 (Eye Movements) Flashcards
Which cranial nerves are involved in the control of the muscles that move the eyes?
3 (III): Oculomotor
4 (IV): Trochlear
6 (VI): Abducens
The frontal eye fields and parieto-occipital regions of the brain do not project directly to the eye movement nuclei of cranial nerves 3, 4 and 6 but to other structures that are involved in eye movement control, true or false?
True
Brainstem gaze centers are above the level of the ________________, and located where?
Oculomotor nucleus
Brainstem, cerebellum, basal ganglia and the cerebral cortex.
What is the function of brainstem gaze centers?
To direct the movements of the eyes, to coordinate and control the response of the eyes to changes in target speed and position, and head position.
Brainstem gaze centers are connected to output nuclei (cranial nerves 3, 4, and 6) by…
Inter-nuclear pathways (circuits)
Horizontal eye movements are controlled by which muscles?
Lateral rectus and medial rectus
The lateral rectus muscle is connected to which cranial nerve nucleus?
Abducens nuclei (cranial nerve 6)
The medial rectus muscle is connected to which cranial nerve nucleus?
Oculomotor nuclei (cranial nerve 3)
The innervation of the eye movement cranial nerve nuclei depends on…
The direction of the eye movement
The paramedian pontine reticular formation (PPRF) is the _________________ gaze center.
horizontal
The paramedian pontine reticular formation is the horizontal gaze center, providing input from input from the cortex, the eyes are “told” which way the should move, this is via a tract called…
the medial longitudinal fasciculus
Tells the eyes which way they should move via connections with cranial nerves
Medial longitudinal fasciculus
The lateral rectus muscle is controlled through connection with which cranial nerve nucleus?
Abducens nuclei (6)
The medial rectus muscle is controlled through connection with which cranial nerve nucleus?
Oculomotor (3)
Neurons projecting from the abducens nucleus (CN 6) have two pathways (projections), what are they?
- The lateral rectus
- Cross and project to the oculomotor nucleus (CN 3) which innervates the medial rectus muscle
Neurons in the abducens nucleus cross and project to the oculomotor nucleus via a tract called…
The medial longitudinal fasciculus
The rostral interstitial nucleus of the MLF and the interstitial nucleus of Cajal, both in the midbrain are ______________ gaze centers.
vertical
The rostral interstitial nucleus of the MLF and the interstitial nucleus of Cajal both project to the ____________ nucleus and the _____________ nucleus thereby controlling the activity of the lower motor neurons that innervate eye muscles involved with vertical movements.
Oculomotor (CN 3)
Trochlear (CN 4)
What is the function of saccadic eye movements?
Bring targets of interest into the field of view and refocus the image on the fovea
Ballistic conjugate eye movements
Saccades
Saccadic eye movements involve direction control, what structure(s) are the horizontal gaze center and the vertical gaze center?
The paramedian pontine reticular formation is the horizontal gaze center.
The rostral interstitial nucleus of the medial longitudinal fasciculus and the interstitial nucleus of Cajal are the vertical gaze centers.
For saccadic eye movements both the __________ and __________ communicate with the horizontal and vertical gaze centers, sending motor commands to move eyes in magnitude/direction specified.
Superior colliculus
Frontal eye fields
Descending input from the ___________ and the _______________ send motor commands to move eyes in magnitude/direction specified (saccades).
Superior colliculus and frontal eye fields.
What type of eye movements require moving stimulus and cannot be carried out voluntarily without a stimulus?
Smooth pursuit eye movements
