What are the extraoccular muscles?
Muscles involved in eyemovement; Lateral Rectus (6); Superior Oblique (4); superior rectus, medial rectus, inferior rectus; inferior oblique (3)
Which extraoccular muscles are innervated by the Abducens nerve?
Which extraocculuar muscle is innervated by the Trochlear nerve?
Which extraoccular muscles are innervated by CN III
superior rectus, medial rectus, inferior rectus, inferior oblique
Which fibre bundle is associated with communication between motor CN nuclei involved in gaze?
Medial longitudinal fasciculus
Where is the MLF at the level of the rostral pons?
Where is the MLF at the level of the caudal pons?
Where is the MLF at the level of the midbrain?
Where is the vertical gaze centre?
Midbrain - reticular formation and pretectal area
Where is the horizontal gaze centre?
Pons - paramedian pontine RF (PPRF)
How many neurons are involved in directing the gaze to the right
4 - 1) the horizontal gaze centre neurons synpapse on the abducens nucleus; IPSI CN VI terminates on the right lateral rectus (LR6); 3) another set of abducens neurons cross the midline and synapse at the OCCULOMOTOR nucleus; 4) occulomotor neurons innervate the ipsilateral medial rectus
What would happen to gaze if there was a lesion to the RIGHT abducens nerve
Ipsilateral (right) eye would fail to abduct when looking to the right; leftward gaze would be unaffected
What is a reflexive saccade?
Visually guided saccade in response to external cue (prosaccade)
What is a volitional saccade
voluntary eye movement
What is the main input for voilutional saccades?
Frontal eye fields in SMA (BA 8)
What is the main input for reflexive saccades
Superior colliculi (brainstem)
Reflexive saccades recruit which structures?
Frontal eye fields --> ipsi superior colliculus --> contralateral horizontal gaze centre --> abducens nucleus --> ipsi lateral rectus and contra occulomotor nucleus --> ipsi left medial rectus
What is found in the DESCENDING MLF?
Medial and lateral vestibulospinal tracts
Which structures are involve in smooth pursuit?
FEF and V1 --> ipsilateral pontine nuclei (cerebropontine) --> contralateral cerebellum --> ipsilateral vestibular nuclei --> contralateral abducens nucleus --> activation of ips CNVI and contra CN III via the MLF
Which direction do eyes move in the VOR
Opposite of the direction of head movement
Which structures are involved in the VOR response to leftward head rotation?
1) Left horizontal canal ---> ipsi vestibular nuclei ---> contra abducens nucleus ---> ipsi CN VI and contra CN III via MLF and occulomotor nucleus
Which muscles are involved in the pupillary reflex?
Which nuclei are involved in pupillary constriction
1) Pretectal; 2) Edinger-Westphal (CN-III GVE)
What are the first step involved in pupillary constriction?
1) light reaches retina; info travels to pre-tectal nuclei in midbrain via optic nerve and optic tract (post-chiasm)
What is the role of the pretectal nuclei in pupillary constriction?
Send bilateral projections to the edinger-westphal nuclei of CN III
What is the role of the edinger-westphal nuclei in pupillary constriction
Send preganglionic efferents (GVEs) to the ciliary ganglia
What happens at ciliary ganglia during pupil constriction?
Receive pre-ganglionic input from edinger-westphal nucleus; send post-ganglionic projections (ciliary nerves) to innervate constrictor pupillae muscles
If parasympathetic fibres in the right CN III were damaged, what would happen when a light was shone into the right eye?
No pupillary constriction in right eye BUT left eye will still constrict; called "blown pupil"
Which fibres cross the optic nerve?
Fibres from the NASAL (medial) half of each retina
Which tract do fibres travel in on their way from the LGN to V1?
Optic radiation (geniculocalcarine tract)