EYE MOVEMENTS - MODULE Flashcards
Which 3 cranial nerves innervate the extraocular muscles
- Abducens (CN VI)
- Trochlear (CN IV)
- Oculomotor (CN III)
What muscle is innervated by the abducens nerve
Lateral rectus
what muscle is innervated by the trochlear nerve
superior oblique
what muscle(s) are innervated by the oculomotor nerve
- Superior rectus
- medial rectus
- inferior rectus
- inferior oblique
What is gaze
the coordinated movements of the right and left eyes to a visual target
How does communication between ocular nuclei occur
via the ascending medial longitudinal fasciculus
what is the medial longitudinal fasciculus
a fiber tract that is critical for coordianted eye movements
Where is the vertical gaze center located
in the midbrain reticular formation and pretectal area
where is the horizontal gaze center located
in the pons - paramedian pontine reticular formation
The horizontal gaze center gives input to the ____ to direct gaze to the _____
abducens nucleus
ipsilateral side
A subset of neurons projects from the abducens nucleus to what muscle
ipsilateral lateral rectus
A second subset of neurons projects from the abducens nucleus to the ___ and the to what muscle
oculomotor nucleus
left medial rectus muscle
What are saccades? What do they allow us to do?
rapid, simultaneous movements of the eyes that redirect the gaze between different fixation points
Allow us to scan the environmetn
what are reflexive saccades
visually guides sacced in response to external cue
What are volitional saccades
voluntary eye movements indenpendent of any visual stimulus
saccadic eye movement can be initiated by ___ or ____
cortical or subcortical areas of the brain
Cortical initiation of saccades comes from..
frontal eye fields located in the supplementary motor areas and extending anteriorly
Cortical initiation of saccades is the main input for..
volitional saccades
subcortical initiation of saccades comes from?
superior colliculus located in the posterior midbrain
subcortical initiation of saccade is the main input for…
reflexive saccades
What is the pathway for reflexive saccades
- this card is frigged im sorry
- Visual stimulus appear in visual field and active contralateral frontal eye field and the contralateral superior colliculus
- within the superior colliculus, neurons in the superficial visual layer are activated and project to corresponding neurons in the deep motor layers
- neurons from superior colliculus activate contralateral horizontal gaze center which then initiated gaze in ipsilateral direction
The descending MLF allows communication between…
nuclei and the brainstem
the descending MLF comprises the ___ and ____
medial and lateral vestibulospinal tracts
The desceding MLF arises from the ____ and influences
Vestibular nuclei and influences muscle tone for balance and posture and it critical in the positioning of the head and neck
In smooth pursuit the 1st step is for the primary visual cortex and the frontal eye fiels to send projections to the…
ipsilateral pontine nuclei
in smooth pursuit, fibres from the pontine nuclei project across the midlines into …
the contralateral cerebellum
In smooth pursuit fibres project from the cerebellum to the…
ipsilateral vestibular nuclei
in smooth pursuit, fibres from the vestibular nuclei cross the midline and project tooo….
the contralateral abducens nucleus
what is the end goal of smooth pursuit
to coordinate movement of both eyes to look in the same direction
What is the vestibulo-ocular reflex
rapid adjustment of eye movement in response to movement of the head (to counteract it)
why do we need to have the vestibulo-ocular reflex
to stabilize image on the retina and prevent the image blurring
how many dimensions does the vestibo-ocular reflex occur in
3 dimensions
what initiates the VOR
shifting of fluid in the horizontal canal (shifts opposite to head movement)
during the VOR when fluid shifts in the horizontal canal what is activated
sensory cells
in the VOR, the sensory cells once activate project to …
the ipsilateral vestibular nuclei
in the VOR, fibres from the vestibular nuclei cross the midline and project to the
contralateral abducens nucleus
in the VOR eyes move in what direction
opposite to the head movement
