Cranial nerves (Chapter 12)

Question 1

Name the 6 different categories of nerve fibers.

Answer 1

Somatic sensory, visceral sensory, special sensory

Somatic motor, visceral motor, branchiomeric

Question 2

Describe the organization of cranial nuclei in the brainstem, from medial -> lateral.

Answer 2

(Motor = medial, sensory = surface)
Somatic motor
Visceral motor
Branchial motor
Autonomic
Visceral sensory
Special sensory

Question 3

What functions are special sensory fibers involved in?

Answer 3

The special sensory nerve fibers are involved in hearing and balance/equilibrium.

Question 4

Name the somatic motor nerves.

Answer 4

The somatic motor nerves are:

Oculomotor (III), Trochlear (IV), Abducens (VI), Hypoglossal (XII)

Question 5

Name the special sensory nerves.

Answer 5

The special sensory nerves are:

Olfactory (I), Optic (II), Vestibulocochlear (VII)

Question 6

Name the branchiomeric nerves.

Answer 6

The branchiomeric nerves are:

Trigeminal (V), Facial (VII), Glossopharyngeal (IX), Vagus (X), Accessory (XI)

Question 7

The oculomotor nerve (III) contains _________ nerve fibers and is involved in…

Answer 7

The oculomotor nerve (III) contains somatic motor fibers.

It is involved in medial eye movements (upward gaze), and pupil reactivity.

Question 8

The trochlear nerve (IV) contains _________ nerve fibers and is involved in…

Answer 8

The trochlear nerve (IV) contains somatic motor fibers.

It is involved in inferior eye movements (down; left-right).

Question 9

The trigeminal nerve (V) contains _________ nerve fibers and is involved in…

Answer 9

The trigeminal nerve (V) contains branchiomeric and somatic sensory fibers.
It is involved in touch, pain, temperature, and proprioceptive information from the face and top of head.

Question 10

The abducens nerve (VI) contains _________ nerve fibers and is involved in…

Answer 10

The abducens nerve (VI) contains somatic motor fibers.

It is involved in lateral eye movements.

Question 11

The facial nerve (VII) contains _________ nerve fibers and is involved in…

Answer 11

The facial nerve (VII) contains branchiomeric, somatic sensory, visceral sensory, and visceral motor fibers.
It is involved in taste (anterior tongue), facial expressions, corneal blink reflex, and swallowing.

Question 12

The glossopharyngeal nerve (IX) contains _________ nerve fibers and is involved in…

Answer 12

The glossopharyngeal nerve (IX) contains branchiomeric, somatic sensory, somatic motor, visceral sensory, and visceral motor fibers.
It is involved in taste (posterior tongue) and swallowing.

Question 13

The vagus nerve (X) contains _________ nerve fibers and is involved in…

Answer 13

The vagus nerve (VII) contains branchiomeric, somatic sensory, somatic motor, visceral sensory, and visceral motor fibers.
It is involved in parasympathetic responses and the gag reflex.

Question 14

The accessory nerve (XI) contains _________ nerve fibers and is involved in…

Answer 14

The accessory nerve (XI) contains branchiomeric nerve fibers.
It is involved in shoulder and neck movements.

Question 15

The hypoglossal nerve (XI) contains _________ nerve fibers and is involved in…

Answer 15

The hypoglossal nerve (XII) contains branchiomeric nerve fibers.
It is involved in tongue movements.

Question 16

Describe the different trigeminal pathways for pain & temperature vs. tactile & proprioceptive afferents.

Answer 16

Spinal trigeminal system (pain & temperature): inputs descend via the spinal tract to the lowest medulla and cross there. They synapse in the spinal trigeminal nucleus and become part of the ascending spinothalamic tract.
Tactile and proprioceptive inputs are sent separately.

Question 17

What is the somatotopic organization of pain and temperature inputs (trigeminal)?

Answer 17

The further toward the back of the head, the more caudal the lesion on the brainstem/spinal cord.

Question 18

Which two cranial nerves are involved in the corneal blink reflex and how does it occur (including fast and slow components)?

Answer 18

The corneal blink reflex involves the trigeminal (opthalmic division) and facial nerves. Trigeminal inputs to the spinal nucleus project bilaterally via the reticular formation to the facial motor nucleus. This causes a blink.
The fast component is due to uncrossed fibers projecting from the trigeminal sensory nucleus to the facial nucleus.
The slow component occurs due to contralateral inputs controlling the eyes.

Question 19

If a patient presents with facial muscle weakness, how would you tell if this was due to damage at the level of facial vs. corticobulbar inputs?

Answer 19

If the facial weakness includes all facial muscles on one side, then likely damage to the facial nucleus or facial nerve. Corticobulbar damage spares upper facial muscles, because corticobulbar inputs are bilateral to upper face, but unilateral for lower face.

Question 20

Mnemonic for cranial nerves in order:

Answer 20

On Old Olympus’ Towering Top A Finn And German Viewed Some Hops

O: olfactory nerve (CN I)
O: optic nerve (CN II)
O: oculomotor nerve (CN III)
T: trochlear nerve (CN IV)
T: trigeminal nerve(CN V)
A: abducens nerve (CN VI)
F: facial nerve (CN VII)
A: auditory (or vestibulocochlear) nerve (CN VIII)
G: glossopharyngeal nerve (CN IX)
V: vagus nerve (CN X)
S: spinal accessory nerve (CN XI)
H: hypoglossal nerve (CN XII)

Question 21

Mnemonic for cranial nerves by function:

Answer 21

Some say marry money but my brother says big brains matter more

S: sensory (olfactory nerve - CN I)
S: sensory (optic nerve - CN II)
M: motor (oculomotor nerve - CN III)
M: motor (trochlear nerve - CN IV)
B: both (trigeminal nerve - CN V)
M: motor (abducens nerve - CN VI)
B: both (facial nerve - CN VII)
S: sensory (vestibulocochlear nerve - CN VIII)
B: both (glossopharyngeal nerve CN IX)
B: both (vagus nerve - CN X)
M: motor (spinal accessory nerve - CN XI)
M: motor (hypoglossal nerve - CN XII)

Question 22

What are the three different divisions of the trigeminal (V)?

Answer 22

3 divisions of the trigeminal: opthalmic, maxillary, and mandibular.