Cranial Nerves

Question 1

What are the somatic motor nuclei and what nerves go with them?

Answer 1

nucleus of oculomotor N (CN 3)

nucleus of trochlear nerve (CN 4)

nucleus of abducent n (CN 6)

nucleus of hypoglossal nerve (CN 12)

Question 2

What are the motor (only) cranial nerves?

Answer 2

occulomotor (3)

trochlear (4)

abducens (6)

accessory (11)

hypoglossal (12)

Question 3

What are the special sensory (only) cranial nerves?

Answer 3

olfactory (1)

optic (2)

vestibulococchlear (8)

Question 4

what are the mixed cranial nerves?

Answer 4

trigeminal (5)

facial (7)

glossopharyngeal (9)

vagus (10)

Question 5

What is anosmia?

Answer 5

olfactory loss

contralateral nostril can compensate for unilateral anosmia

causes: head trauma, viral infections, intracranial lesions, nose obstruction, aging

Question 6

What is the halo sign?

Answer 6

clear drainage that separates from blood = suggests presence of CSF

can leak from nose = CSF rhinorrhea w/ fracture of cribiform plate

Question 7

What can happen to the olfactory n during a head injury?

Answer 7

olfactory fila can be sheared off at cribiform plate

Question 8

What is the pathway of the optic nerve?

Answer 8

evaginations of diencephalon –> optic canal of the sphenoid bone –> orbit

Question 9

What is the optic nerve tract formed by?

Where are cell bodies?

Answer 9

axons of retinal ganglion cells

cell bodies in the retina

Question 10

What can the pituitary gland do to CN II?

Answer 10

can press on optic chiasm –> loss of vision laterally in both visual fields

Question 11

What are the 2 functionso f the oculomotor n?

Answer 11

GSE: motor to intra-ocular and 4 extra-ocular ms

GVE: PS innervation to pupil and ciliary Ms

Question 12

What is the tract of the oculomotor n?

Answer 12

leaves the midbrain –> pierces dura lateral to diaphragma sellae –> runs in lateral wall of cavernous sinus –> enters orbit via superior orbital fissure

splits into superior and inferior divisions in the orbit

Question 13

Where do the PS fibers travelling w/ the oculomotor n synapse?

Answer 13

at the ciliary ganglion –> go thru short ciliary ns

Question 14

What happens in oculomotor palsy?

Answer 14

unable to maintain normal eye alignment

characteristic down and out pos in affected eye

strabismus and double vision, ptosis (droopy eyelid) and myadriasis (pupil dilation)

Question 15

What is the tract of the trochlear N?

Answer 15

exits dorsal surface of midbrain –> pierces dura mater at margin of the tentorium cerebelli –> runs in lateral wall of cavernous sinus –> enters orbit of superior orbital fissure

Question 16

What is the tracto of the abducens n?

Answer 16

emerges from brainstem btw pons and medulla –> traverses pontine cistern –> pierces dura covering clivus –> runs in cavernous sinus near ICA –> exits orbit via superior orbital fissure