Cranial Nerves

Question 1

Describe the olfactory nerve:

Answer 1

Innervates nasal mucosa for sense of smell
Pass superiorly through cribriform plate
Enter olfactory bulb
Signal travels back to brain via olfactory tract
Sensory nerve
Most anterior
Cranial nerve I

Question 2

Describe the optic nerve:

Answer 2

Sensory nerves of retina travel to the brain via optic nerves
May cross at the optic chiasm
Travel in the optic tracts back to the brain
Sensory nerve
Exits brain via optic canal
Cranial nerve II

Question 3

Describe the oculomotor, trochlear and abducens nerves:

Answer 3

Cranial nerves III, IV, VI
Control the 6 muscles that move the eye
Oculomotor constricts pupils - parasympatehtic innervation
Motor nerves
Exit the brain via the superior orbital fissure

Question 4

Describe the trigeminal nerve

Answer 4

Cranial nerve V
Forms a ganglion either side of the pituitary fossa and divides into;

V1 Ophthalmic division - exits via superior orbital fissure
V2 Maxillary division - exits via Foramen rotundum
V3 Mandibular division - exits via Foramen ovale & spinosum

Sensory innervation;
- V1-3
- face, orbital, teeth, meninges, nasal + oral cavities

Motor innervation;
- V3
- muscles of mastication
- Mylohyoid & Digastric
- 2 small muscles in the ear & palate

Question 5

Describe the sensory innervation branches of the trigeminal nerve:

Answer 5

Supraorbital nerve - skin of forehead
Branches of nasociliary - tip of nose
Infraorbital - skin inferior to the eye
Lingual - anterior tongue
Mental - skin of chin

Question 6

Describe the facial nerve:

Answer 6

Cranial nerve VII
Enters internal acoustic meatus then facial canal
Exits via stylomastoid foramen
Supplies muscles of facial expression
Mixed nerve as sensory + motor innervation

Branches along route to supply;
- stapedius
- Digastric & stylohyoid muscles in neck
- taste in anterior tongue
- parasympathetic innervation to submandibular salivary gland and lacrimal gland of eye

Question 7

Describe the vestibulocohlear nerve:

Answer 7

Cranial nerve VIII
Exits brain via internal acoustic meatus
Sensory nerve
Supplies organs of vestibule and cochlea

Question 8

Describe the glossopharyngeal nerve:

Answer 8

Cranial nerve IX
Exits the brain via jugular foramen
Mixed nerve
Runs alongside Stylopharyngeus muscle Enters pharynx & contributes to pharyngeal plexus

Sensory innervation;
- pharynx
- carotid sinus, baroreceptor for blood pressure
- carotid body, chemoreceptor for blood oxygenation
- taste on posterior tongue

Motor innervation;
- Stylopharyngeus
- parasympathetic to parotid salivary gland

Question 9

Describe the vagus nerve:

Answer 9

Cranial nerve X, mixed nerve
Exits brain via jugular foramen
Runs;
- superficial to scalene muscles
- lateral to sympathetic chain
- medial to phrenic nerve

Motor branches - palate, pharynx and larynx
Continues into thorax and abdomen to provide parasympathetic innervation

Question 10

Describe the spinal accessory nerve:

Answer 10

Technically arises from spinal cord
Passes up through Forman Magnum and enters jugular Forman
Runs with carotid artery down neck
Innervates sternocleidomastoid and trapezius
Cranial nerve XI, motor nerve

Question 11

Describe hypoglossal

Answer 11

Exits brain via hypoglossal canal
Cranial nerve XII
Runs anteriorly towards submandibular triangle of neck
Motor innervation to hypoglossus, genioglossus, styloglossus and intrinsic muscles of the tongue