Motor Innvervation

Question 1

What muscle(s) does the oculomotor nerve innvervate?

Answer 1

Superior division: superior rectus and levatorInferior division: medial rectus, inferior rectus, and inferior oblique.

Question 2

Where is the oculomotor nucleus located?

Answer 2

In the midbrain at the level of the superior colliculus, just ventral to the cerebral aqueduct.

Question 3

True or false: each of the subnuclei within the occulomotor nucleus controls the ipsilateral muscle.

Answer 3

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.

Question 4

Where do the fibers from CN III exit?

Answer 4

They exit just medial to the cerebral peduncles and with in the interpeduncular fossa.

Question 5

Does CN III pass near any arteries as it runs forward?

Answer 5

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.

Question 6

What is the last area CN III passes through before it enters the orbit?

Answer 6

The cavernous sinus, near the sella turcica.Running superior to inferior along the lateral wall of the cavernous sinus:**OculomotorTrochlearOphthalmicMaxillary

Question 7

Through which opening does CN III enter the orbit?

Answer 7

Through the superior orbital fissure, INSIDE of the oculomotor foramen.

Question 8

True or false: By the time CN III has entered the orbit, it has already split into the superior and inferior divisions.

Answer 8

True.

Question 9

What muscle(s) does the trochlear nerve innvervate?

Answer 9

The superior oblique.

Question 10

Where is the trochlear nucleus located?

Answer 10

In the midbrain at the level of the inferior colliculus, anterior to the cerebral aqueduct.

Question 11

True or false: Fibers from CN IV exit just below fibers from CN III.

Answer 11

False. Fibers from CN IV actually travel dorsally (unlike all other cranial nerves).

Question 12

Is CN IV innervation ipsilateral or contralateral?

Answer 12

Contralateral; it crosses as it emerges from the dorsal aspect of the midbrain.

Question 13

Where do the fibers from CN IV exit?

Answer 13

They exit just inferior to the inferior colliculus. They then curve around the cerebral peduncle at the upper border of the pons.

Question 14

Does CN IV pass near any arteries as it runs forward?

Answer 14

Yes, it passes between the superior cerebellar artery and the posterior cerebral artery.

Question 15

What is the last area CN IV passes through before it enters the orbit?

Answer 15

The cavernous sinus, near the sella turcica.Running superior to inferior along the lateral wall of the cavernous sinus:Oculomotor**TrochlearOphthalmicMaxillary

Question 16

Through which opening does CN IV enter the orbit?

Answer 16

Through the superior orbital fissure, ABOVE the oculomotor foramen.

Question 17

What muscle(s) does the abducens nerve innvervate?

Answer 17

The lateral rectus muscle.

Question 18

Where is the abducens nucleus located?

Answer 18

Near the inferior dorsal midline of the pons, beside the floor of the fourth ventricle.

Question 19

What two types of neurons are found in the abducens nucleus?

Answer 19

Motor neurons for innervating the lateral rectus muscle, and internuclear neurons for innervating the contralateral medial rectus muscle. This facilitates smooth saccades.

Question 20

What course does CN VI run on its way to the orbit?

Answer 20

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.

Question 21

Through which opening does CN VI enter the orbit?

Answer 21

Through the superior orbital fissure, INSIDE of the oculomotor foramen.

Question 22

What is the purpose of the corticonuclear tract?

Answer 22

It contains fibers that connect the cerebral hemispheres to the nuclei of CN III, CN IV, and CN VI.

Question 23

What is the purpose of the tectobulbar tract?

Answer 23

It connects the superior colliculus to the nuclei of CN III, CN IV, and CN VI.

Question 24

What is the purpose of the medial longitudinal fasciculus?

Answer 24

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.

Question 25

Where is the motor nucleus of the facial nerve (CN VII) located?

Answer 25

In the reticular formation of the pons.

Question 26

The upper segment of the motor nucleus of CN VII supplies which muscles?

Answer 26

Frontalis, procerus, corrugator superciliaris, and orbicularis.

Question 27

What is the action of the orbicularis?

Answer 27

Closes the lid.

Question 28

What is the action of frontalis, corrugator superciliaris, and procerus?

Answer 28

Move the eyebrows.

Question 29

What route does CN VII follow as it exits the brainstem?

Answer 29

Exiting at the lower border of the pons, it enters the internal acoustic foramen and exits through the stylomastoid foramen, and goes on to supply its muscles.

Question 30

What is the action of Müller’s muscle?

Answer 30

Widens the palpebral fissure. (It is sympathetically innervated.)

Question 31

What is Sherrington’s law?

Answer 31

Increased innervation at an agonist muscle is accompanied by an equal decrease of innervation to the antagonist muscle.

Question 32

What is Herring’s law?

Answer 32

Equal innervation is sent to yoked muscles.

Question 33

Which nerves enter/exit the orbit through the superior orbital fissure above the oculomotor foramen?

Answer 33

The lacrimal nerve, the frontal nerve, and the trochlear nerve.

Question 34

Which nerves enter/exit the orbit through the superior orbital fissure within the oculomotor foramen?

Answer 34

The oculomotor nerve (both superior and inferior divisions), and the nasociliary nerve.

Question 35

Superior to inferior, what is the order of the nerves that pass through the lateral wall of the cavernous sinus?

Answer 35

OculomotorTrochlearOphthalmicMaxillary