Module 8 - The Visual System Flashcards
The extraocular muscles are innervated by 3 different cranial nerves - which nerve innervates the:
- lateral rectus
- superior oblique
- all other eye muscles
- lateral rectus - abducens (CN VI)
- superior oblique - trochlear (CN IV)
- All other eye muscles - oculomotor (CN III)
What is the mnemonic for remembering extraocular eye muscle innervation?
LR6 SO4 - all the rest are 3
Locate the oculomotor nerve (CN III) on this image and micrograph of the brainstem
Locate the trochlear nerve (CN IV) on the below images
Locate the abducens on this image.
Gaze refers to?
The coordinated movements of the right and left eyes to a visual target
In order to coordinate synergistic eye movements, the nuclei of cranial nerves III, IV, and VI need to communicate with one another both ipsilaterally and contralaterally. How does communication between these nuclei occur?
Via the ascending medial medial longitudinal fasciculus (MLF)
What is the ascending MLF critical for?
Coordinated eye movements
On this midbrain micrograph, locate the oculomotor nerve and the medial longitudinal fasciculus.
On this rostral pons micrograph, locate the trochlear nerve roots and the ascending MLF
On this caudal pons pons micrograph, locate the abducens nuclei and the ascending MLF
Coordinated horizontal and vertical movement of both eyes is facilitated by gaze centers in the brainstem. Where is the:
- vertical gaze center
- horizontal gaze center
What are saccades?
Rapid simultaneous movements of the eyes that redirect the gaze between different fixation points
What are the two major types of saccades?
Reflexive saccades
Volitional saccades
What is a reflexive saccade?
Visually guided saccade in response to external cues
What is a reflexive saccade?
Visually guided saccade in response to external cues
What is a volitional saccade?
Voluntary eye movements, independent of any visual stimulus
Saccadic eye movements can be initiated by X or Y areas of the brain.
cortical
subcortical