Cranial Nerves

Question 1

Draw out the brain, and identify all the sites of cranial nerve exit.

Answer 1

Refer to Notion.

Question 2

What are the twelve cranial nerves?

Answer 2

1. Olfactory
2. Optic
3. Oculomotor
4. Trochlear
5. Trigeminal
6. Abducens
7. Facial
8. Vestibulocochlear
9. Glossopharyngeal
10. Vagus
11. Spinal Accessory
12. Hypoglossal

Question 3

What are the main anatomical divisions of the cranial nerves?

Answer 3

1. Exit from above brainstem (I, II)
2. Exit from midbrain (III, IV)
3. Exit from pons (V - VIII)
4. Exit from medulla oblongata and spinal cord (IX - XII)

Question 4

What are the main functional divisions of the cranial nerves?

Answer 4

1. Olfactory unit
2. Optic division
3. Facial division
4. Auditory unit
5. Oral division
6. Others

Question 5

Draw out the skull, and identify the cranial nerve exits (superior, posterior, and others view).

Answer 5

Refer to Notion.

Question 6

What does the olfactory unit consist of?

Answer 6

CN I - Olfactory (Sensory)

Question 7

What does the olfactory nerve transmit?

Answer 7

Smell

Question 8

Draw the olfactory nerve pathway.

Answer 8

Refer to Notion.

Question 9

What does the facial division consist of?

Answer 9

CN V - Trigeminal (Mixed)
CN VII - Facial (Mixed)

Question 10

What does the trigeminal sensory nerve transmit?

Answer 10

Sensory info (general; face)

Question 11

Draw the trigeminal sensory nerve pathway.

Answer 11

Refer to Notion.

Question 12

What does the trigeminal motor nerve transmit?

Answer 12

Motor signals (discrete, skilled) to four muscles of mastication, mylohyoid, anterior belly of digastric, and tensors

Question 13

Draw the trigeminal motor nerve pathway.

Answer 13

Refer to Notion.

Question 14

What does the facial sensory nerve transmit?

Answer 14

• Sensory info (general) from external ear
• Taste from anterior 2/3 of tongue

Question 15

Draw the facial sensory nerve pathway.

Answer 15

Refer to Notion.

Question 16

What does the facial sensory nerve transmit?

Answer 16

• Motor signals (discrete, skilled) to facial muscles of expression, stylohyoid, pos. belly of digastric muscle + stapedius
• Parasympathetic innervation of submandibular / sublingual glands, lacrimal glands, and mucous glands of the oral and nasal cavities

Question 17

Draw the facial motor nerve pathway.

Answer 17

Refer to Notion.

Question 18

Draw the corneal blink reflex pathway.

Answer 18

Refer to Notion.

Question 19

What does the auditory unit consist of?

Answer 19

CN VIII - Vestibulocochlear (Sensory)

Question 20

What does the vestibulocochlear nerve transmit?

Answer 20

Hearing and balance

Question 21

Draw the vestibulocochlear nerve pathway.

Answer 21

Refer to Notion.

Question 22

What does the oral division consist of?

Answer 22

• CN IX - Glossopharyngeal (Mixed)
• CN X - Vagus (Mixed)
• CN XI - Hypoglossal (Motor)

Question 23

What does the glossopharyngeal sensory nerve transmit?

Answer 23

1. Sensory info (general) from posterior 1/3 of tongue, circumvate papillae, pharynx, and ear
2. Taste from posterior 1/3 of tongue and circumvate papillae
3. Visceral sensory info from carotid body / sinus

Question 24

Draw the glossopharyngeal sensory nerve pathway.

Answer 24

Refer to Notion.

Question 25

What happens to visceral sensory info transmitted from carotid body / sinus?

Answer 25

1. Sent via glossopharyngeal nerve to solitary nucleus 2. Integrated, sent to dorsal vagal nucleus 3. Visceral motor info sent out to cardiac ganglia via vagus motor nerve

Question 26

What does the glossopharyngeal motor nerve transmit?

Answer 26

- Motor signals (discrete, skilled) to stylopharyngeus muscle - Visceral innervation of parotid gland

Question 27

Draw the glossopharyngeal motor nerve pathway.

Answer 27

Refer to Notion.

Question 28

What does the vagus sensory nerve transmit?

Answer 28

1. Sensory info (general) from pharynx, larynx, oesophagus, ear, and postcranial fossa 2. Taste from epiglottis 3. Visceral sensory info from CVS, GIT, and RS

Question 29

What happens to visceral sensory info transmitted to vagus sensory nerve?

Answer 29

1. Sent via vagus nerve to solitary nucleus 2. Integrated and sent to dorsal vagal nucleus 3. Visceral motor info sent out to cardiac ganglia via vagus motor nerve

Question 30

Draw the vagus sensory nerve pathway.

Answer 30

Refer to Notion.

Question 31

What does the vagus motor nerve transmit?

Answer 31

1. Motor signals (discrete, skilled) to muscles of soft palate (excl. tensors), pharynx (excl. stylopharyngeus), and larynx 2. Visceral motor signals to smooth muscles and glands of CVS, GIT, and RS

Question 32

Draw the vagus motor nerve pathway.

Answer 32

Refer to Notion.

Question 33

What does the hypoglossal nerve transmit?

Answer 33

Motor signals (discrete, skilled) to tongue muscles (excl. palatoglossus)

Question 34

Draw the hypoglossal nerve pathway.

Answer 34

Refer to Notion.

Question 35

Draw the gag reflex pathway.

Answer 35

Glossopharyngeal (Aff) > Vagus (Eff)

Question 36

What does the spinal accessory nerve transmit?

Answer 36

Motor signals (discrete, skilled) to SCM and trapezius

Question 37

Draw the spinal accessory nerve pathway.

Answer 37

Refer to Notion.

Question 38

What does the optic division consist of?

Answer 38

- CN II - Optic (Sensory) - CN III - Oculomotor (Motor) - CN IV - Trochlear (Motor) - CN VI - Abducens (Motor)

Question 39

What does the optic nerve transmit?

Answer 39

Visual info

Question 40

Draw the optic nerve pathway.

Answer 40

Refer to Notion.

Question 41

What does the oculomotor nerve transmit?

Answer 41

- Motor innervation of 5 extra-ocular muscles (except SO4 and LR6) + levator palpebrae superioris - Parasympathetic motor innervation of ciliary muscles + sphincter pupillae muscles

Question 42

Draw the oculomotor nerve pathway.

Answer 42

Refer to Notion.

Question 43

What does the trochlear nerve transmit?

Answer 43

- Motor innervation of superior oblique

Question 44

Draw the trochlear nerve pathway.

Answer 44

Refer to Notion.

Question 45

What does the abducens nerve transmit?

Answer 45

- Motor innervation of lateral rectus

Question 46

Draw the abducens nerve pathway.

Answer 46

Refer to Notion.

Question 47

Describe the pupillary light reflex.

Answer 47

- CN II > LGN > pretectal nucleus > cortex > EWN > CN III > sphincter pupillae muscles > miosis - Shining light in one eye affects both eyes, due to bilateral innervation of EWN

Question 48

Describe the pupillary accommodation reflex, when accommodating for near vision.

Answer 48

- CN II > LGN > pretectal nucleus > cortex > EWN > CN III > ciliary muscles + sphincter pupillae muscles + medial rectus - ciliary muscles contract to make lens more globular for near vision - sphincter pupillae muscles contract > miosis - medial rectus muscles contract > convergence to focus on object

Question 49

What is the only CN nuclei that is unilaterally / contralaterally innervated?

Answer 49

- Facial motor nuclei, which supplies lower facial muscles - In a CNS injury, most nuclei may retain function due to having bilateral innervation - Contralateral lower facial muscles affected first (e.g. stroke = face drooping first)