Cranial nerves

Question 1

Cranial nerves

Answer 1

12 bilaterally paired nerves, which carry both afferent and efferent fibres between the brain and peripheral structures, principally of the head and neck. CN I and II attach directly to the forebrain, while CN III-XII connect to cranial nerve nuclei within the brainstem.

Question 2

Cranial nerve nuclei

Answer 2

Groups of cell bodies of 10 of the cranial nerves, located within the brainstem.

Question 3

CN I

Answer 3

Olfactory nerve; responsible for olfaction (sense of smell)

-special sensory afferent neurones innervate the olfactory epithelium in the nasal cavity

Question 4

CN II

Answer 4

Optic nerve; responsible for vision and the pupillary light reflex
-special sensory afferent neurones innervate the retina

Question 5

CN III

Answer 5

Oculomotor nerve; responsible for movement of the eyeball, elevation of the upper eyelid. pupillary constriction and lens accomodation

• motor neurones innervate 4 of the 6 extraocular muscles (sup., med., inf. rectus, inf. oblique) and the levator palpebrae superioris
• parasympathetic neurones innervate the sphincter pupillae and ciliary muscle

Question 6

CN IV

Answer 6

Trochlear nerve; responsible for movement of the eyeball

-motor neurones innervate 1 of the extraocular muscles (sup. oblique)

Question 7

CN V

Answer 7

Trigeminal nerve; composed of opthalmic, maxillary and mandibular nerves, responsible for general sensation, mastication, dampening loud noises, and events during swallowing

• sensory neurones innervate the face, scalp, cornea, nasal and oral cavities, cranial dura mater
• motor neurones innervate the muscles of mastication, tensor tympani, and tensor veli palitini

Question 8

CN VI

Answer 8

Abducens nerve; responsible for movement of the eyeball

-motor neurones innervate 1 of the extraocular muscles (lat. rectus)

Question 9

CN VII

Answer 9

Facial nerve; responsible for facial movement, swallowing, jaw movement, dampening loud noises, taste, lacrimation, mucous secretion and salivation

• motor neurones innervate the muscles of facial expression and stapedius muscle
• special sensory afferent neurones innervate the anterior 2/3 of the tongue
• parasympathetic neurones innervate the lacrimal glands, mucous glands of the nose, palate and sinuses, sublingual and submandibular salivary glands

Question 10

CN VIII

Answer 10

Vestibulocochlear nerve; responsible for hearing, equilibration (balance) and vestibular sensation (position and movement of the head)
-special sensory afferent neurones innervate the vestibular apparatus and cochlea

Question 11

CN IX

Answer 11

Glossopharyngeal nerve; responsible for general sensation, taste, baroreception, chemoreception, swallowing and salivation

• sensory neurones innervate the pharynx, posterior 1/3 of the tongue, Eustachian tube and middle ear
• special sensory afferent neurones innervate the posterior 1/3 of the tongue, carotid sinus and carotid body
• motor neurones innervate the stylopharyngeus muscle
• parasympathetic neurones innervate the parotid salivary gland

Question 12

CN X

Answer 12

Vagus nerve; responsible for general sensation, visceral sensation, chemoreception, baroreception, taste, speech, swallowing, innervation of cardiac muscle, innervation of smooth muscle and glands of cardiovascular ssystem, respiratory and GI tracts

• sensory neurones innervate the pharynx, larynx, trachea, oesophagus and external ear
• special sensory afferent neurones innervate the thoracic and abdominal viscera, aortic bodies, aortic arch and epiglottis
• motor neurones innervate the soft palate, pharynx, larynx and upper oesophagus
• parasympathetic neurones innervate the thoracic and abdominal viscera

Question 13

CN XI

Answer 13

Accessory nerve; responsible for the movement of the head and shoulder
-motor neurones innervate the sternomastoid and trapezius muscles

Question 14

CN XII

Answer 14

Hypoglossal nerve; responsible for the movement of the tongue, speech and swallowing
-motor neurones innervate the extrinsic and intrinsic muscles of the tongue