8 CRANIAL NERVES

Question 1

Cranial nerve I

Answer 1

Olfactory nerve. S. Allocortex/ limbus.
400 free nerve endings in respiratory epithelium. Travels via olfactory foramen in cribiform plate (ethmoid bone) to olfactory bulb then allocortex.

Question 2

Cranial nerve II

Answer 2

Optic nerve. S. Midbrain
Input from retinal cells which form optic disc then, optic nerve, to optic chiasma (decussates here), travels via optic canal to lateral geniculate body of thalamus and superior colliculus before primary visual cortex.

Question 3

Cranial nerve III

Answer 3

Oculomotor. M. Midbrain.
Controls muscles: inferior rectus, inferior oblique, medial rectus and superior rectus and constriction of pupil.
Travels via superior orbital fissure

Question 4

Cranial nerve IV

Answer 4

Trochlear. M. Pons
Controls the superior oblique eye muscle.
Travels via the superior orbital fissure

Question 5

Cranial nerve V

Answer 5

Trigeminal. B. Pons
3 divisions;
V1- ophthalmic branch. Sensation from forehead, eyelid, top of nose. Exits via superior orbital fissure
V2- Maxillary. Sensation on medial side of face, nose and top lip and maxillary teeth. Exits via the foramen rotundum.
V3- Mandibular. Both nerve. Sensation to lateral side of face, ear, jaw and teeth. Motor to chewing muscles. Exits the skull via foramen ovale.

Question 6

Cranial nerve VI

Answer 6

Abducens. M. Pons.

Motor to eye muscle Lateral Rectus- peripheral vision. Exits via superior orbital fissure

Question 7

Cranial nerve VII

Answer 7

Facial. B. Medulla
Sensory from external acoustic meatus, and auricle. Taste. Innervates lacrimal gland, some salivary glands and mucous membranes. Innervates muscles of the face and scalp. exits via stylomastiod foramen.

Question 8

Cranial nerve VIII

Answer 8

Vestibulocochlear. S. Medulla

Sensory for hearing and balance. Exits via external acoustic meatus.

Question 9

Cranial nerve IX

Answer 9

Glossopharyngeal. B. Medulla
Sensory from carotid body and sinus, sensory from tongue, tonsils, oropharynx, parts of ear. Innervates parotid salivary gland and stylopharynges muscle. Exits via jugular foramen

Question 10

Cranial nerve X

Answer 10

Vagus. B. Medulla.
Sensory throat, pharynx, epiglottis, and skin of ear, Sensory from chemoreceptors, baroreceptors, viscera, taste, smooth muscle innervation of digestive tract. Exits via jugular foramen.

Question 11

Cranial nerve XI

Answer 11

Accessory nerve. M. Medulla.

Innervate the sternocleidomastoid and trapezius muscle. Exits via jugular foramen.

Question 12

Cranial nerve XII

Answer 12

Hypoglossal. M. Medulla.

Inenrvates tongue muscle, key in speech and swallowing. Exits via hypoglossal canal.

Question 13

What nerve is affected in anosmia and how may this nerve be injured

Answer 13

Olfactory (inability to detect odours). Cribiform plate fracture.

Question 14

What may an orbital fracture result in

Answer 14

Optic nerve damage. Loss of visual acuity/ visual field defects.

Question 15

What may occur with damage to the oculomotor nerve?

Answer 15

Ptosis (drooping of upper eyelid), diploplia (double vision), stabismus (cross eyes)

Question 16

What is trigeminal neuralgia

Answer 16

Sudden severe shock like pain that courses along the trigeminal nerve divisions. Incidence 1:8000

Question 17

What may result from viral infection of cranial nerve VII

Answer 17

Bells palsy, loss of taste, decreased salivation, loss of ability to close eyes even during sleep

Question 18

What may a vestibular schwannoma cause

Answer 18

Damage to cranial nerve VII. Hearing loss, vertigo, tinnitus

Question 19

What would damage to cranial nerve IX cause

Answer 19

Difficulty in swallowing, reduced secretion of saliva, loss of sensation in the throat, loss of taste sensation.

Question 20

What would damage to the vagus nerve cause

Answer 20

Interrupted sensation from abdominal and thoracic viscera. Dysphagia. paralysed vocal cords. Tachycardia.

Question 21

Damage to cranial nerve XI

Answer 21

Inability to raise shoulders and turn head

Question 22

Damage to cranial nerve XII

Answer 22

Difficulty in chewing, speaking and swallowing. The tongue when protruded curls towards the affected side and the affected side atrophies.