L18 Cranial Nerves 2

Question 1

Describe cranial nerve I.

Answer 1

Olfactory nerve

• Not a true cranial nerve
• Brain tract
• Short olfactory axons run from olfactory epithelium to olfactory glomeruli in the olfactory bulb

Question 2

Describe cranial nerve II.

Answer 2

Optic nerve

• Not a true cranial nerve
• Nerve tract
• Joins the retina to the forebrain

Question 3

Which cranial nerves innervate the extrinsic eye muscles?

Answer 3

• CN III (oculomotor) provides GSE fibres to most exstrinsic eye muscles, as well as GVE fibres to ciliary muscles and pupillary constrictor muscle
• CN IV (trochlear) provides GSE fibres to superior oblique muscle
• CN VI (abducens) provides GSE fibres to lateral rectus muscle muscle

Question 4

Describe the GSA neurons of cranial nerve V.

Answer 4

Trigeminal nerve

• Carries GSA innervation from the face, mouth, nasal cavity, dura and anterior 2/3rds of the tongue
• Divided into ophthalmic, maxillary and mandibular branches

Question 5

Describe the SVE neurons of cranial nerve V.

Answer 5

Trigeminal nerve

• Carries SVE neurons to innervate muscles of mastication, biting and swallowing
• SVE neurons in mandibular branch of CN V innervate tensor tympani muscle and tensor veli palatini muscle

Question 6

Which branches of the facial nerve (VII) innervate the lacrimal and salivary glands?

Answer 6

• Lacrimal nerve carries GVE facial nerve fibres to lacrimal gland
• Lingual nerve carries fibres to sublingual and submandibular salivary glands, and carries SVA fibres from tongue

Question 7

Describe cranial nerve VII.

Answer 7

Facial nerve

• SVE to muscles of facial expression
• GVE to oral mucosa, nasal mucosa and lacrimal glands
• GVE to sublingual and submandibular glands
• SVA to provide taste to anterior 2/3rds of tongue

Question 8

Describe cranial nerve VIII.

Answer 8

Vestibulocochlear nerve

• SSA neurons to innervate organ of corti in the cochlea
• SSA neurons to innervate vestibular canals

Both located within the petrous temporal bone of the skull.

Question 9

Describe cranial nerve IX.

Answer 9

Glossopharnygeal nerve

• SVA to provide taste to posterior third of tongue
• GVA to carotid sinus and body and posterior third of tongue and pharynx
• GVE to parotid gland
• SVE to stylopharyngeus (elevates pharynx for swallowing and gagging)

Question 10

Describe cranial nerve X.

Answer 10

Vagus nerve, exits cranial cavity via jugular foramen

• SVA, taste to epiglottis
• GVA to larynx, pharynx, heart, lungs gut etc
• GVE to heart and smooth muscle of bronchioles and gut
• SVE from nucleus to ambiggus to pharynx and larynx

Question 11

Describe cranial nerve XI.

Answer 11

Spinal accessory nerve

• SVE innervation to sternocleidomastoid (head rotation)
• SVE to upper trapezius (shoulder blade movement)

Question 12

Describe cranial nerve XII.

Answer 12

Hypoglossal nerve

- GSE fibres only to intrinsic and extrinsic tongue muscles