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•Distinguish the cranial nerves and categorize if the nerve is sensory, motor, or mixed and its major function(s).

There are twelve cranial nerves. They exit the brain in an orderly fashion. Two, olfactory and optic, are located in the telencephalon. Two, occulomotor and trochlear, are located in the midbrain. Four, trigeminal, abducens, facial and acoustovestibular, are located in the pons. The remaining four, glossopharyngeal, vagus, accessory and hypoglossal are located in the medulla.
It is most useful however to discuss them, not related to location, but rather as to function.

There are three cranial nerves with primarily sensory functionCranial nerve I, Olfactory, modulates smell, cranial nerve II, Optic,modulates vision. Cranial nerve VIII, Acoustovestibular, modulates hearing and balance.

There are four cranial nerves with primarily motor function. CN IV, Trochlear, innervates the superior oblique muscle of the eyeball. CN VI, Abducens, innervates the lateral rectus muscle of the eyeball and abducts the eye. CN XI, Accessory, innervates the trapezius muscle in the back and shoulders. CN XII, Hypoglossal, innervates the muscles of the throat and enables us to swallow.

Five cranial nerves have mixed sensory, motor and parasympathetic function. These five will be discussed in detail here. The mixed cranial nerves are CN III Occulomotor, CN V Trigeminal, CN VII Facial, CN IX Glossopharyngeal and CN X Vagus.

The occulomotor nerve exits the brain at the midbrain in the middle of the cerebral peduncle. As such it is compressed whenever there is swelling of the brain and herniation through the tentorium. This results in a dilated pupil which is unreactive to light. A clinical phenomenon known as a "blown" pupil. This signals dire consequences and brain death unless the condition is quickly treated.

The occulomotor nerve supplies four of the six eyeball muscles.. It also carries Parasympathetic input to the ciliary ganglion to constrict pupil.

The trigeminal is a large important nerve which carries Sensory input from the face, cornea, mouth, nose and temporomandibular joint. Nerve impulses travel from the face to the trigeminal ganglion which is located at the base of the skull, to the nucleus in the medulla. The stimulus finally travels to the Ventral Posterior Medial thalamus.

The trigeminal nerve also supplies motor innervation to the muscles of mastication.

The Facial nerve carries taste sensation from the anterior 2/3 tongue. Link to taste. It also supplies Motor function to the muscles of facial expression. Paralysis of the facial nerve causes a facial droop. Finally it carries Parasymapathetic input to the salivary and lacrimal glands.

The Glossopharyngeal nerve carries taste sensation from the posterior 1/3 tongue. It also carries general sensation from the auditory tube and pharynx. This is why ear problems commonly cause funny sensations in the throat. It also supplies Parasympathetic input to the parotid gland.

Last, but certainly not least, is the Vagus. It supplies general sensory and motor function to the larynx and pharynx.

Perhaps most importantly it supplies Parasympathetic input to the heart and lungs and gastro intestinal tract to the level of the splenic flexure of the colon.

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