W20-L4: Cranial Nerves

Question 1

Which Cranial nerves are purely sensory?

Answer 1

CNI, CNII, CNVIII

Question 2

Which Cranial nerves are purely motor?

Answer 2

CN III, IV, VI, XI and XII

Question 3

Which Cranial nerves are mixed?

Answer 3

CN V, VII, IX, X

Question 4

Where is the somatic motor nerve column?

Answer 4

Most medial

Question 5

Where are the nuclei in the somatic motor nerve column?

Answer 5

Midbrain: Oculomotor, trochlear
Pons: Abducens
Medulla: Hypoglossal

Question 6

Where is the brachial motor nerve column?

Answer 6

2nd from the medial line

Question 7

Where are the nuclei in the brachial motor nerve column?

Answer 7

Pons: Trigeminal motor nucleus (V3), Facial nucleus
Medulla: Nucleus ambiguus (CN IX, X)
Spinal cord: accessory nucleus

Question 8

What is the function of the visceral efferents and where is the column?

Answer 8

Most lateral of the motor columns (medial 3), function is motor innervation to smooth muscles (autonomic)

Question 9

Where are the nuclei in the visceral efferents column?

Answer 9

Midbrain: Edinger-Westphal nucleus
Pons: Superior salivatory nucleus (CN VII)
Medulla: Inferior salivatory nucleus (CN IX), Dorsal motor nucleus of the vagus

Question 10

Where is the visceral afferent sensory column?

Answer 10

Most medial of the sensory columns

Question 11

Where are the nuclei in the visceral afferent sensory column?

Answer 11

Extends from pons to level of nucleus gracilis: nucleus of the solitarus tract (CN VII, IX, X)

Question 12

What are the parts of the nucleus solitarius?

Answer 12

Rostral: Gustatory nucleus (CN VII, IX, X)
Caudal: Visceral sensory division (IX, X)

Question 13

Where is the somatic sensory column?

Answer 13

Middle of the three sensory lateral columns

Question 14

Where are the nuclei in the somatic sensory column?

Answer 14

Midbrain: Mesencephalic trigeminal nucleus
Pons: Principle sensory trigeminal nucleus
Pons to spinal cord: Spinal trigeminal tract (CN V, VII, IX, X)

Question 15

Where is the special sensory column?

Answer 15

Most lateral of all the columns

Question 16

Where are the nuclei in the special sensory column?

Answer 16

Pons and medulla: More medial is vestibular nuclei

Pons: Lateral is cochlear nuclei

Question 17

What is a cause of CN I disruption that causes a noxious smell?

Answer 17

Meningoma that impinges on the nerve

Question 18

What does the oculomotor nerve do?

Answer 18

• Motor:
– Extrocular muscles: MR, SR, IR, IO
– Elevates eyelid-via levator palpebrae superioris
• PS to eye:
– Iris (pupils)
– Ciliary muscle (focussing)

Question 19

Where does CN III, IV and VI pass through together and why is this important?

Answer 19

Cavernous sinus and superior orbital fissure, so lesion in this area could affect them all

Question 20

Where does CN III and VI go through together?

Answer 20

common tendinous ring

Question 21

Pupillary light reflex

Answer 21

Sensory inputs to brain from retina via CNII.

Motor outputs to Sphincter Pupillae muscle in iris:
-PS fibres from Edinger Westphal nucleus.

Tests midbrain function

Question 22

What does CN V do?

Answer 22

– Sensory: input from face and also inside of mouth

– Motor: Muscles of mastication and Tensor tympani (inner ear)

Question 23

What are the principle sensory and spinal trigeminal nucleus analogous to in the spinal cord?

Answer 23

Dorsal column & Anterolateral system.

Question 24

What does the mesencephalic trigeminal nucleus do?

Answer 24

Proprioception of the face

Question 25

How does the trigeminal nerve exit the brainstem?

Answer 25

Two roots: motor and sensory

Question 26

What is the difference in the two roots of the trigeminal nerve?

Answer 26

Sensory forms the trigeminal ganglion, motor travels under the ganglion

Question 27

Corneal blink reflex

Answer 27

• Sensory inputs to brainstem are mediated via CNV1.
• Motor outputs to eyelid (Orbicularis oculi) are mediated by CNVII.
• Used as a test of pontine function

Question 28

What does the facial nerve do?

Answer 28

Motor (facial nerve proper):
– Innervates the muscles of facial expression.
– Stapedius muscle (ear) which dampens sounds

Parasympathetic:
• Lacrimal & sublingual and submandibular salivary glands

Taste:
• from anterior 2/3rds of tongue and soft palate

Sensation:
• from a small region near the external auditory meatus.

Question 29

What is the course of the facial nerve?

Answer 29

Gives off branch to tear ducts, stapedius and tongue then exits stylomastoid foramen and gives off posterior auricular and then T, Z, B, M and C branches

Question 30

What does CN IX do?

Answer 30

Sensory: from tongue (post. 1/3), pharynx, middle ear and carotid body.
Taste: post. 1/3 tongue
Visceral motor: PS to parotid
Motor: stylopharyngeus

Question 31

What is the course of CN IX?

Answer 31

CN IX exits skull via jugular foramen lateral to and in front of CNX, CNXI and forms the Superior and inferior ganglia. Then Follows the stylopharyngeus to reach the oropharynx and tongue.

Question 32

What does the vagus nerve do?

Answer 32

• Motor: to many striated muscles
– soft palate, pharynx, larynx, upper oesophagus and 1 tongue muscle.
• PS to many organs,
– from pharynx to upper abdomen. 
• Sensory:
– from pharynx, larynx oesophagus 
• Visceral:
– Input from baro and chemorecptors of the Aortic arch

Question 33

Gag reflex

Answer 33

• Sensory inputs: IX-sensory to pharynx
• Motor outputs: X-motor to pharynx
• Used as a test of medulla function

Question 34

What is the course of CN XI?

Answer 34

Spinal accessory nucleus is in the upper 5-6 of cervical spinal cord. Nerve enters cranium via Foramen magnum. Then travels with X roots and exits jugular foramen.

Question 35

What is the function of CN XI?

Answer 35

Provides motor input to sternomastoid and upper part of trapezius.

Question 36

A lesion of CN XI on one side will cause an inability to turn to which side?

Answer 36

Contralateral side