cranial nerves

I

Olfactory

Special sensory, for smell. Consists of small bundles of fibres passing from the nerve endings in the olfactory epithelium, through perforated bone at the top of the nose, to enter the olfactory bulb, underneath the frontal lobe.

II

Optic

Special sensory, for vision. Made up of fibres that converge from the whole of the retina. Pass backwards to the base of the brain from the back of the eyeballs.

III

Oculomotor

Mainly motor to small muscles that move the eyeball. Also carry autonomic (parasympathetic) nerve fibres that constrict the pupil.

IV

Trochlear

Mainly motor to the muscle that turns the eyeball downwards and outwards.

V

Trigeminal

The largest of the cranial nerves, with 3 main divisions: ophthalmic, maxillary, and mandibular. Mainly sensory, from most of the tissues of the head, face, and mouth; motor to the muscles that move the lower jaw.

VI

Abducens

Motor to the muscle that moves the eyeball outwards.

VII

Facial

Motor to the facial muscles; sensory, for taste, from the front part of the tongue; also parasympathetic nerve fibres to salivary glands.

VIII

Auditory (vestibulo-cochlear)

Mainly sensory, for hearing and balance; enter the brain from the inner ear (cochlea and vestibule).

IX

Glossopharyngeal

Sensory and motor, for the mouth, neck, including pharynx, larynx, and tongue (taste from the back part); also transmit sensory information concerning blood gases and blood pressure from the neck arteries; parasympathetic fibres to salivary glands.

X

Vagus

Carry visceral sensory information from thoracic and abdominal organs; motor to the larynx (speech) and oesophagus (swallowing); parasympathetic to heart, lungs, and to muscle and glands of the alimentary tract as far as the middle of the colon.

XI

Accessory

Shares the functions of X, and joins with uppermost spinal nerves to innervate muscles that move the head and shoulders.

XII

Hypoglossal

Motor to the tongue muscles.