Cranial Nerves

The cranial nerves are numbered sequentially in relation to their position from the front of the brain to the back. There are 12 pairs of cranial nerves which emerge from the underside of the brain and pass through the foramina in the base of the skull. Cranial nerves I, II, and VIII are pure sensory nerves. Cranial nerves III, IV, VI, XI, and XII are pure motor nerves. Cranial nerves V, VII, IX, and X are mixed sensory and motor nerves.

  1. The olfactory nerve (CN I) contains special sensory neurons concerned with smell.

  2. The optic nerve (CN II) contains sensory neurons dedicated to vision.

  3. The oculomotor nerve (CN III) provides motor function for all eye muscles except those supplied by cranial nerves IV and VI.

  4. The trochlear nerve (CN IV) provides motor function to the superior oblique muscle of the eye.

  5. The trigeminal nerve (CN V) is the principal sensory supply to the head (face, teeth, si­nuses, etc.); it also provides motor function to the muscles of mastication.

  6. The abducens nerve (CN VI) provides motor function to the lateral rectus muscle of the eye.

  7. The facial nerve (CN VII) provides motor innervation to the muscles of facial expression, lacrimal gland, submaxillary gland, sublingual gland, as well as sensory supply to the anterior two-thirds of the tongue.

  8. The acoustic nerve (CN VIII), also known as the vestibulocochlear nerve, provides sen­sory innervation for hearing and equilibrium.

  9. The glossopharyngeal nerve (CN IX) provides motor innervation to the pharyngeal mus­culature and sensory function to the posterior one-third of the tongue and pharynx.

  10. The vagus nerve (CN X) provides motor innervation to the heart, lungs, and gastrointes­tinal tract. It also provides sensory innervation to the heart, respiratory tract, gastrointes­tinal tract, and external ear.

  11. The accessory nerve (CN XI) provides motor function to the sternocleidomastoid and trapezius muscles.

  12. The hypoglossal nerve (CN XII) is a pure motor nerve that innervates the muscles of the tongue.