Motor Innvervation Flashcards
(35 cards)
What muscle(s) does the oculomotor nerve innvervate?
Superior division: superior rectus and levatorInferior division: medial rectus, inferior rectus, and inferior oblique.
Where is the oculomotor nucleus located?
In the midbrain at the level of the superior colliculus, just ventral to the cerebral aqueduct.
True or false: each of the subnuclei within the occulomotor nucleus controls the ipsilateral muscle.
False. Each of them control the ipsilateral muscle EXCEPT for the subnucleus for the superior rectus. Its fibers cross immediately, passing through the through the opposite superior rectus subnucleus.
Where do the fibers from CN III exit?
They exit just medial to the cerebral peduncles and with in the interpeduncular fossa.
Does CN III pass near any arteries as it runs forward?
Yes, it passes between the superior cerebellar artery and the posterior cerebral artery. It also passes lateral and slightly inferior to the posterior communicating artery of the circle of Willis.
What is the last area CN III passes through before it enters the orbit?
The cavernous sinus, near the sella turcica.Running superior to inferior along the lateral wall of the cavernous sinus:**OculomotorTrochlearOphthalmicMaxillary
Through which opening does CN III enter the orbit?
Through the superior orbital fissure, INSIDE of the oculomotor foramen.
True or false: By the time CN III has entered the orbit, it has already split into the superior and inferior divisions.
True.
What muscle(s) does the trochlear nerve innvervate?
The superior oblique.
Where is the trochlear nucleus located?
In the midbrain at the level of the inferior colliculus, anterior to the cerebral aqueduct.
True or false: Fibers from CN IV exit just below fibers from CN III.
False. Fibers from CN IV actually travel dorsally (unlike all other cranial nerves).
Is CN IV innervation ipsilateral or contralateral?
Contralateral; it crosses as it emerges from the dorsal aspect of the midbrain.
Where do the fibers from CN IV exit?
They exit just inferior to the inferior colliculus. They then curve around the cerebral peduncle at the upper border of the pons.
Does CN IV pass near any arteries as it runs forward?
Yes, it passes between the superior cerebellar artery and the posterior cerebral artery.
What is the last area CN IV passes through before it enters the orbit?
The cavernous sinus, near the sella turcica.Running superior to inferior along the lateral wall of the cavernous sinus:Oculomotor**TrochlearOphthalmicMaxillary
Through which opening does CN IV enter the orbit?
Through the superior orbital fissure, ABOVE the oculomotor foramen.
What muscle(s) does the abducens nerve innvervate?
The lateral rectus muscle.
Where is the abducens nucleus located?
Near the inferior dorsal midline of the pons, beside the floor of the fourth ventricle.
What two types of neurons are found in the abducens nucleus?
Motor neurons for innervating the lateral rectus muscle, and internuclear neurons for innervating the contralateral medial rectus muscle. This facilitates smooth saccades.
What course does CN VI run on its way to the orbit?
It runs along the occipital bone and up over the petrous ridge and enters the cavernous sinus near the lateral wall of the internal carotid artery.
Through which opening does CN VI enter the orbit?
Through the superior orbital fissure, INSIDE of the oculomotor foramen.
What is the purpose of the corticonuclear tract?
It contains fibers that connect the cerebral hemispheres to the nuclei of CN III, CN IV, and CN VI.
What is the purpose of the tectobulbar tract?
It connects the superior colliculus to the nuclei of CN III, CN IV, and CN VI.
What is the purpose of the medial longitudinal fasciculus?
It provides a connection in order to coordinate eye movements with the vestibular apparatus. The vestibular nucleus, the oculomotor nucleus, the abducens nucleus, and the trochlear nucleus are all connected.
