Cranial nerves

The cranial nerves emerge from the base of the brain and lead to muscles and sense organs in the head and neck for the most part. The twelve pairs of cranial nerves with their functions are as follows:

• Olfactory nerve (I): Sensory nerve that carries impulses for smell to the brain.
• Optic nerve (II): Sensory nerve that carries impulses for vision to the brain.
• Oculomotor nerve (III): Motor nerve that carries impulses to the extrinsic eye muscles, which help direct the position of the eyeball. This nerve also carries impulses to the muscles that regulate the size of the pupil.
• Trochlear nerve (IV): Motor nerve that carries impulses to one extrinsic eye muscle (the superior oblique muscle). Once again, this muscle helps regulate the position of the eyeball.
• Trigeminal nerve (V): A mixed nerve. The sensory fibers of this nerve carry impulses for general sensation (touch, temperature and pain) associated with the face, teeth, lips and eyelids. The motor fibers of this nerve carry impulses to some of the mastication muscles of the face.
• Abducens nerve (VI): A mixed nerve, but primarily a motor nerve. This nerve carries impulses to the lateral rectus muscle of the eye. This muscle is an extrinsic eye muscle that is involved in positioning the eyeball.
• Facial nerve (VII): A mixed nerve. The sensory fibers of this nerve carry taste sensations from the tongue. The motor fibers of this nerve carry impulses to many of the muscles of the face and they carry impulses to the lacrimal, submandibular, and sublingual glands.
• Vestibulocochlear nerve (VIII): A sensory nerve that carries impulses for hearing and equilibrium from the ear to the brain.
• Glossopharyngeal nerve (IX): A mixed nerve. The sensory fibers of this nerve carry basic sensory information and taste sensations from the pharynx and tongue to the brain. The motor fibers of this nerve carry impulses associated with swallowing to the pharynx.
• Vagus nerve (X): A mixed nerve. The sensory fibers of this nerve carry impulses from the pharynx, larynx, and most internal organs to the brain. The motor fibers of this nerve carry impulses to internal organs of the chest and abdomen and to the skeletal muscles of the larynx and pharynx.
• Accessory nerve (XI): A mixed nerve, but primarily motor. Carries impulses to muscles of the neck and back.
• Hypoglossal nerve (XII): Primarily a motor nerve. This nerve carries impulses to the muscles that move and position the tongue.