The cranial nerves are 12 pairs of nerves that emerge from the brain stem to innervate various areas of the face and some other regions of the body. The face needs to be capable of a number of different movements which require precision and control, making it necessary to have numerous nerves to handle different types of movements. These nerves fit through several holes in the skull that have been specifically designed to accommodate them; the holes can be seen when a person closely examines a skull.
In order from I to XII, the cranial nerves are the olfactory nerve, optic nerve, oculomotor nerve, trochlear nerve, trigeminal nerve, abducens nerve, facial nerve, vestibulocochlear nerve (also known as the auditory vestibular nerve), glossopharyngeal nerve, vagus nerve, spinal accessory nerve (or accessory nerve), and hypoglossal nerve. One common mnemonic used to remember the names is "on old Olympus' towering tops, a Finn and German viewed some hops," also sometimes rendered as "on old Olympus' towering tops, a famous vocal German viewed some hops."
The function of the olfactory nerve is to handle the sense of smell, through the olfactory bulb located behind the nose. The optic nerve is responsible for vision, while the oculomotor nerve is one of the nerves which moves the eye. The trochlear nerve is also involved in eye movement, while the trigeminal nerve is used for chewing and provides sensory feedback about touch and pain in the face and head.
The abducens nerve controls eye movement, while the facial nerve is partially responsible for taste along with facial movements. The vestibulocochlear is involved in the sense of balance. The glossopharyngeal nerve picks up tastes in the back the tongue and is responsible for some of the muscle movements involved in swallowing. The vagus handles input from the viscera, and the spinal accessory nerve is responsible for head movements. The 12th, the hypoglossal, is responsible for moving the tongue.
Learning all the cranial nerves can seem intimidating at first, but as people study facial anatomy, they become familiar with the different areas these nerves innervate, making it easier to remember which nerve does what. Many charts illustrating the nerves can be found online, along with images that show the paths the nerves take to various areas of the face and head. Damage to these nerves can cause a wide variety of problems including palsy, paralysis, and interference with vision, smell, taste, and touch.