Day 4 - Cranial Nerves

Question 1

Damage to the olfactory nerve will cause what? What about to the inferior temporal lobe?

Answer 1

Ipsilateral loss of smell

Damaged to inf. temporal lobe can cause olfactory hallucinations

Question 2

How is the optic nerve involved in the pupillary light reflex?

Answer 2

Light is sensed in the optic nerve and is sent to the pretectal nucleus

Fibers from pretectual nucleus project to Edinger-Westphal nucleus of CN III (oculomotor). CNIII innervates bilateral musculature for pupillary constriction (so both pupils will constrict even if light is just in one eye).

Question 3

Why does oculomotor nerve palsy cause depression and lateral abduction of the eye?

Answer 3

Because all of the eye muscles are weakened EXCEPT the muscles innervated by trochlear and abducens nerves. Therefore, the eye moves in the directions of strength, which are lateral and inferior.

Question 4

List all of the sx. of oculomotor nerve palsy

Answer 4

1. Lateral and inferior strabismus
2. Diplopia (double vision)
3. Ptosis (eyelid droop)
4. Mydriasis (pupil dilated)
5. No lens accomodation

Question 5

The oculomotor nucleus receives axons from a number of structures - list them here

Answer 5

• Oculomotor nerve
• Superior colliculus
• Medial longitudinal fasciculus (connects nuclei of CN III, IV, VI, VIII)

Question 6

What is the impact of the trochlear nerve fibers crossing prior to exiting the brainstem?

Answer 6

No clinical relevence.

Question 7

Name the 3 branches of the Trigeminal nerve (CN V)

Answer 7

1. Opthalmic (forehead)
2. Maxillary (mid face)
3. Mandibular (jaw, lower face)

Question 8

Which brainstem nucleus associated with the Trigeminal nerve innervates the muscles of mastication?

Answer 8

Trigeminal motor nucleus

Question 9

Which nucleus associated with Trigeminal nerve receives sensory information (touch, pressure, vibration)?

Answer 9

Chief sensory nucleus

Question 10

Which nucleus associated with the trigeminal nerve receives sensory info related to pain and temperature?

Answer 10

Spinal Trigeminal nucleus

Question 11

Abducens nucleus receives axons another structure (aside from the abducens nerve) - what is it?

Answer 11

Medial longitudinal fasciculus

Question 12

List the exceptions to contralateral UMN innervation in the cranial nerves

Answer 12

CN VII (facial) - contralateral UMN innervation to lower face
CN X (vagus) - contralateral innervation to palate/uvula
CN XI (accessory) - contralateral innervation to trapezius (ips. to SCM)
CN XII (hypoglossal) - contralateral innervation of geneoglossus muscle

Question 13

What does the geneoglossus muscle do?

Answer 13

Depresses and protrudes tongue (bilateral contraction)

Deviates tongue contralaterally (unilateral contraction)

Question 14

Which cranial nerves are part of the parasympathetic nervous system?

Answer 14

Facial
Glossopharyngeal
Vagus
Oculomotor

Question 15

Describe the pathway, nerves, and nuclei involved in the gag reflex

Answer 15

Touch felt at pharynx by afferent fibers of CN IX (glossopharyngeal) -> sensation sent to spinal trigeminal nucleus -> cross midline of brainstem -> go up trigeminal lemniscus -> reach nucleus ambiguus on BOTH sides -> motor response produced by CN X (vagus)

Question 16

Where does the vagus nerve enter/exit the skull?

Answer 16

Jugular foramen