Cranial nerve IV trochlear nerve Flashcards
Where is the nucleus of CN IV
caudal midbrain at lever of inferior colliculus
Describe how axons from left trochlear nucleus leave and get to superior oblique muscle
Axos from left trochlear nerve decussate across the midbrain to orm the right trochlear nerve and innervate the right superior oblique muscle (GSE)
Which muscle does Cranial nerve VI innervate?
lateral rectus (GSE)
Where is abducens nucleus located?
caudal pons
what does the abducens nerve traverse?
superior orbital fissure
Do motor nuclei of CN III IV and VI receive direct input from motor cortices?
No they do not
What mediates rapid eye movements?
from projections from cortical eye fields (frontal supplementary and parietal eye fields) to the reticular formation (midbrain and pons) The reticular formation projects to motor nuclei of CN III IV and VI which innervate extraocular eye muscles
What is smooth pursuit used for?
track visual stimuli that are moving, they req continuous feedback from visual cortex cortical eye fields, vestibular system and cerebellum to the motor nuclei of CN III CN IV and CN VI.
What can cause medial strabismus?
lesion that affects cranial nerve VI which innervates the lateral rectus, meaning the eye can’t try to abduct when it looks straight ahead, There is no damage to cranial nerve III so the medial rectus is unopposed and the eye abducts
Oculomotor CN III nerve lesion
ipsilateral eye is deviated laterally and slightly downward. Lateral deviation happens because lateral rectus is unopposed, downward position happens because superior oblique is unopposed. However the superior rectus, inferior rectus and inferior oblique have lost their innervation. This causes diplopia (double vision)
Also causes Ptosis- drooping of eyelid bc of deficient innervation to levator palpebrae superioris muscle. and
Dilated non reactive pupil- because of lack of parasympathetic innervation to pupillary constrictor muscle.
