Lecture 4: Cranial Nerves

Question 0

Glossopharyngeal nerve does what?

Answer 0

Motor to stylopharyngeus muscle and parotid gland

Sensory to taste of posterior 2/3 of tongue, general sensation to tonsilar sinuses, pharynx and middle ear cavity

Question 1

Vestibulocochlear nerve does what?

Answer 1

Vestibulo: sensory to equilibrium and motion
Cochlear: sensory to hearing

Question 2

Olfactory nerve does what?

Answer 2

Sensory to smell

Question 3

Optic nerve does what?

Answer 3

Sensory to vision

Question 4

Oculomotor nerve does what?

Answer 4

Motor to extrinsic muscles of the eye ( except superior oblique and lateral rectus) , ciliary muscles and sphincter pupillae

Question 5

Trochlear nerve does what?

Answer 5

Motor to superior oblique muscle

Question 6

Trigeminal nerve does what?

Answer 6

Motor to muscles of mastication

Sensory to face, teeth and sinus

Question 7

Abducens nerve does what?

Answer 7

Motor to lateral rectus muscle

Question 8

Facial nerve does what?

Answer 8

Motor to muscles of facial expression, submandibular, sublingual and lacrimal glands
Sensory to anterior 2/3 of tongue

Question 9

Vagus nerve does what?

Answer 9

Motor: larynx, pharynx, trachea, bronchial tree, heart, G.I tract to left colic flexure and palate
Sensory: larynx, pharynx, trachiobrochial tree, heart, lungs and G.I tract to left colic flexure

Question 10

Spinal accessory nerve does what?

Answer 10

Motor to SCM and trapezius

Question 11

Hypoglossal nerve does what?

Answer 11

All intrinsic and extrinsic muscles of the tongue

Question 12

Olfactory nerve 1

Answer 12

Only nerve to enter cerebrum directly
Special Sensory
Travels through cribriform plate
Special visceral afferent
Olfactory nerve fibres synapses with mitral cells in olfactory bulb
Post synaptic axons form the olfactory tract
Terminates in the piriform cortex of temporal bone

Question 13

Optic nerve 2

Answer 13

Special sensory to vision
Extension of forebrain
Terminate in lateral geniculate bodies of thalamus.
Post-synaptic axons to visual cortex in occipital lobe.

Question 14

Oculomotor nerve 3

Answer 14

Somatic MOTOR (general somatic efferent) &
proprioceptive to:
* 4/6 extraocular muscles (superior, medial and inferior recti; inferior oblique)
*Superior eyelid (levator palpebrae superioris)

• Visceral motor (general visceral efferent –
parasympathetic).
*Post-synaptic fibres from ciliary ganglion to ciliary
muscle and sphincter pupillae muscle
Exit via superior orbital fissure

Question 15

Trochlear nerve 4

Answer 15

• Smallest cranial nerve!
• Only nerve to originate on dorsal aspect of brainstem!
• Longest intra-cranial course!
Somatic MOTOR (general somatic efferent) and
proprioceptive to superior oblique.
Exits via superior orbital fissure

Question 16

Trigeminal nerve 5

Answer 16

Three branches or trigeminal nerve

• Ophthalmic nerve CN V1 exiting brain through orbit
• Maxillary nerve CN V2 exiting brain through foramen rotundum
• Mandibular nerve CN V3 exiting brain through foramen ovale

Question 17

Mandibular nerve

Answer 17

• Mandibular nerve (CN V3) is MOTOR supply to:
* muscles of mastication;
*mylohyoid;
*anterior belly of digastric;
*Tensor veli palatini;
*Tensor tympani.
Muscles of mastication are medial and lateral ptyergoids, masseter and temporlis

Question 18

Abducens 6

Answer 18

• Longest intra-dural course!

* Supplies somatic MOTOR and proprioceptive fibres to LATERAL RECTUS muscles (abducts the eyes)

Question 19

Facial nerve 7

Answer 19

• Longest intra-osseous course of any cranial nerve!
Cranial exit: stylomastoid foramine
*Secretomotor fibres originating in facial nerve are distributed to the lacrimal gland & submandibular/sublingual (salivary) glands
Sensory to anterior 2/3 of tongue
Chorda tympani => special sensory (taste) to anterior tongue
Lingual nerve (from CN V3) => general sensation (touch/temp)
to anterior tongue
Parasympathetic (secretomotor) => * Pterygopalatine ganglion
* Submandibular ganglion
Motor to muscles of facial expression:
Orbicularis oris, orbicularia oculi, buccinator, platysma and occipitofrontalis

Question 20

Vestibulocochlear nerve 8

Answer 20

• Special sensory (special somatic afferent):
hearing/equilibrium/motion.
• Divides into vestibular and cochlear nerves.
• Cochlear nerve: sensory to spiral organ (for sense of hearing).
• Disturbances of cochlear function include deafness and tinnitus (ringing in ears).
• Vestibular nerve: sensory to semicircular ducts/saccule/utricle (for sense of equilibrium).
• Disturbances of vestibular function include vertigo (dizziness) and nystagmus (uncontrollable pendular movement of eyes).

Question 21

Glossopharyngeal nerve 9

Answer 21

MOTOR innervation to stylopharyngeus muscle.
• SECRETOMOTOR to parotid gland:
* Pre-synaptic parasympathetic fibres to otic
ganglion.
• Post-synaptic parasympathetic fibres to parotid
gland.
• SENSORY (general and special (taste)) innervation to posterior 1/3 of tongue; pharynx; tympanic cavity; carotid body and
sinus.
Exits cranium via jugular foremen

Question 22

Vagus nerve 10

Answer 22

• The Wanderer!!
• Longest and most extensive distribution of all thecranial nerves!
• MOTOR to muscles of pharynx.
• SENSORY to pharynx, larynx and reflex afferent (gag reflex).
• Pre-synaptic parasympathetic fibres to involuntary
muscles/glands of tracheobronchial tree; oesophagus; heart; digestive tract (up until left colic flexure).
• Left and right vagi become anterior/posterior in abdomen.

Question 23

Spinal accessory nerve 11

Answer 23

• Cranial exit = jugular foramen.
• Somatic MOTOR to sternocleidomastoid and trapezius muscles.
• Pain and proprioceptive fibres to these muscles via cervical plexus (C2-C4).

Question 24

Hypoglossal nerve 12

Answer 24

Exits cranium via hypoglossal canal
• Emerges anterior surface of medulla oblongata between the pyramid and olive.
• MOTOR to all muscles of tongue (except palatoglossus): styloglossus, hyoglossus, genioglossus.