Cranial Nerves

The cranial nerves are twelve pairs of nerves which stem from various places on the underside of the brain. The first pair comes from the cerebrum. The others all originate at the brain stem. They pass from these locations through the skull and lead to parts of the head, neck and trunk of the body. Although most cranial nerves are mixed, some of them which are associated with special senses, such as smell and vision, contain only sensory fibers. Others that are closely involved with the activities of the muscles and glands are made up of mostly motor fibers and have limited sensory functions. When sensory fibers are present, the neuron cell bodies that are connected to the fibers are located outside the brain and are usually in groups called "ganglia" (one cell is a "ganglion"). Most motor neuron cell bodies, however, are usually found within the gray matter of the brain. Cranial nerves are designated with by number or by name. If a number is used, it refers to the order in which the nerves arise from the front or back areas of the brain; names signify their function or the distribution of the nerve fibers. "Keeping a stiff upper lip" means to control the feelings and not to show pain or emotion. This expression is not related to the true anatomy, however, because when a person cries, it's the muscles in the lower lip that quiver.