ABSTRACT
Cranial nerves can have motor function, sensory function and parasympathetic function, and can thus be composed of motor neurons, sensory neurons and parasympathetic neurons. CN I is responsible for smelling, also called olfaction, and is virtually never tested clinically. CN II transmits visual information to the occipital lobe, where it is processed and interpreted. Together, CN III, CN IV and CN VI control eye movements. CN III also helps to keep the eye open and plays a role in determining pupillary size. CN V provides sensory innervation of the face, and controls muscles involved in chewing, also called mastication. CN VII controls all the other muscles in the face, receives taste from anterior two-thirds of the tongue and innervates many glands in the head. CN VIII is involved in both hearing and balance. CN IX and X both provide sensory and motor innervation to the throat. In addition, CN X provides much of the parasympathetic innervation to the body. CN XI controls turning of the head and shrugging the shoulders. Finally, CN XII controls the tongue.
