Cranial Nerves

Question 1

Corneal reflex
How?
Afferent limb
Efferent limb

Answer 1

Approach from the side of their eye and touch the cornea
Ophthalmic division of the trigeminal nerve
Facial nerve - orbicularis oculi contracts

Question 2

If sense of FLAVOUR is lost, what nerve is most likely damaged?

Answer 2

CN I - Olfactory

Question 3

Name the 2 muscles that open the eye

Answer 3

Levator palpebrae superioris muscle

Superior tarsal muscle

Question 4

What nerve innervates the superior tarsal muscle?

Answer 4

Sympathetic nerve

Question 5

What nerve innervates the levator palpebrae superioris muscle?

Answer 5

Parasympathetic fibres of the oculomotor nerve CN III

Question 6

Describe a lower motor neurone lesion of the facial nerve and give an example of this condition

Answer 6

You will have ipsilateral paralysis of all of the muscles of facial expression (so there is NO forehead sparing)

Bell’s palsy

Question 7

A patient has paralysis of only their lower half of their face.

Is this a UMN lesion or a LMN lesion?

Is the lesion of the contralateral or ipsilateral neurones?

Give possible sites of this lesion.

Why is the lower half of the face only affected?

Answer 7

UMN lesion

Contralateral

Primary motor cortex or corticobulbar tracts

Due to the upper half of the face having bilateral innervation so is unaffected by unilateral UMN lesions

Question 8

What innervates the temporomandibular joint?

And where does this nerve branch off from?

Answer 8

Auriculotemporal nerve (mandibular branch of trigeminal nerve)

Question 9

Discuss the route of olfactory nerve fibres from the roof of the nasal cavity

Answer 9

Go up through the cribriform plate (of the the ethmoid bone) -> olfactory bulb -> olfactory tract -> temporal lobe

Question 10

Describe the route of the oculomotor nerve from the midbrain

Answer 10

Midbrain -> lateral wall of cavernous sinus -> superior orbital fissure -> muscles in eye orbit

Question 11

Which cranial nerve has the longest intracranial route and why?

Answer 11

Trochlear nerve CN IV because it emerges from the dorsal aspect of the brainstem, rather than the ventral side, like the rest of the cranial nerves

Question 12

What nerves and vein exit via the superior orbital fissure?

Answer 12

Oculomotor nerve
Trochlear nerve
Ophthalmic nerve
Abducens nerve
Superior ophthalmic vein

Question 13

Describe the route of the maxillary nerve from the trigeminal ganglion

Answer 13

Foramen rotundum -> pterygopalatine fossa

Question 14

Describe the route of the mandibular nerve from the trigeminal ganglion

Answer 14

Foramen ovale -> infratemporal fossa

Question 15

What nerve enters the bony canal of the mandible then exits through the mental foramen as the mental nerve?

Answer 15

Inferior alveolar nerve

Question 16

What is the motor function of the glossopharyngeal nerve?

Answer 16

Motor innervation to stylopharyngeus muscle (aid swallowing)

Question 17

What is the autonomic function of the glossopharyngeal nerve?

Answer 17

Parasympathetic innervation to the parotid gland

Question 18

What nerve receives general sensation from middle ear and inner tympanic membrane?

Answer 18

Glossopharyngeal nerve

Question 19

What does the vagus nerve have general sensation to?

Answer 19

Lower pharynx
Whole larynx
External ear
Tympanic membrane

Question 20

What does the vagus nerve have motor innervation to?

Answer 20

MUSCLES OF:
Pharynx
Larynx
Soft palate

Question 21

What are the parasympathetic functions associated with the vagus nerve?

Answer 21

Innervation of:

Heart’s:
1. SAN and AVN (↓HR)

Smooth muscle in:

1. GI tract (including oesophagus)
2. Resp tract (including trachea)

Mucosal glands in:

1. Pharynx
2. Larynx
3. Resp tract
4. GI tract

Question 22

Describe the mechanism behind a carotid sinus massage to correct supra-ventricular tachycardia.

Answer 22

Massaging the carotid sinus, which is innervated by CN IX, stimulates the glossopharyngeal nerve (afferent limb) to send impulses to the vagus nerve (efferent limb). Parasympathetic fibres of the vagus nerve send more impulses to the SAN and AVN, signalling a reduction in impulses released from the SAN and AVN so HR ↓