SM_16b: Overview of the Cranial Nerves: I-IV and VI

Question 1

Olfactory nerve (I) exits the ____ of the ____

Answer 1

Olfactory nerve (I) exits the cribriform plate of the ethmoid bone

Question 2

Primordium for the olfactory nerve is the ____

Answer 2

Primordium for the olfactory nerve is the olfactory placode

Question 3

Olfactory epithelium is in the ___

Answer 3

Olfactory epithelium is in the upper nasal cavity / septum

Question 4

Olfactory tract is an extension of the ____ surrounded by ____, while nerves are ____

Answer 4

Olfactory tract is an extension of the brain surrounded by meninges, while nerves are short

Question 5

Respiratory epithelium has ____ for smell

Answer 5

Respiratory epithelium has bipolar neurons for smell

Question 6

Optic nerve (II) runs with the ____ through the ____ of the ____

Answer 6

Optic nerve (II) runs with the ophthalmic artery through the optic canal of the lesser wing of the sphenoid

(special sensory for vision)

Question 7

Describe the different visual field deficits with nerve injury

Answer 7

Different visual field deficits with nerve injury

• Medial half of each visual field crosses over

Question 8

Primordium of optic nerve (II) is the ____

Answer 8

Primordium of optic nerve (II) is the optic cup

• Optic cup is ectodermal extension of the brain surrounded by meninges
• Increase in CSF pressure can compress the optic nerve
• Inner layer gives rise to the visual retina, while the outer layer gives rise to the pigmented retina

Question 9

____, ____, and ____ exit the superior orbital fissure

Answer 9

Oculomotor (III), trochlear (IV), and abducens (VI) nerves exit the superior orbital fissure

Question 10

Oculomotor nerve (III) is somatomator to ____ and presynaptic for ____

Answer 10

Oculomotor nerve (III) is somatomator to all extraocular muscles except lateral rectus and superior oblique and presynaptic parasympathetic for ciliary muscle and pupil constrictor

Question 11

Trochlear nerve is somatomotor to ____, which moves the pupil ____

Answer 11

Trochlear nerve is somatomotor to the superior oblique muscle, which moves the pupil down and out

(clinical testing position: move pupil in, then down)

Question 12

Clinically test the trochlear nerve by moving the pupil ____ then _____

Answer 12

Clinically test the trochlear nerve by moving the pupil in then down

(trochlear nerve is somatomotor to the superior oblique muscle, which moves the pupil down and out)

Question 13

Abducens nerve (VI) is somatomotor to the ____, which ____ the pupil

Answer 13

Abducens nerve (VI) is somatomotor to the lateral rectus, which abducts the pupil

Question 14

Primordia for oculomotor (III), trochlear (IV), and abducens (VI) nerves are ____

Answer 14

Primordia for oculomotor (III), trochlear (IV), and abducens (VI) nerves are pre-otic head somites

Question 15

Parasympathetics from ___ nerve enter the ciliary ganglion

Answer 15

Parasympathetics from oculomotor nerve (III) enter the ciliary ganglion

Question 16

If the oculomotor nerve (III) is injured, there is no ____ function, so the pupil is ____ because there are no ____ input

Answer 16

If the oculomotor nerve (III) is injured, there is no levator palpebrae superioris function, so the pupil is dilated because there are no parasympathetic input

Question 17

If the oculomotor nerve (III) is injured, the pupil stays ____ and ____ because the ____ and ____ are still working

Answer 17

If the oculomotor nerve (III) is injured, the pupil stays down and out because the lateral rectus and superior oblique are still working

Question 18

Abducens palsy leads to ____

Answer 18

Abducens palsy leads to abduct the pupil

(CN VI has a long intracranial course and is often damaged as it gets stretched over the petrous part of the temporal bone)