brain, spinal cord, and nerve disorders
Nerves
Cranial nerves and spinal nerves
 directly connect the brain and the brain stem with the eyes, ears, nose, and throat and with various parts of the head, neck, and trunk. There are 12 pairs of them (see Overview of the Cranial Nerves ). Cranial nerves transmit sensory information, including touch, vision, taste, smell, and hearing. connect the spinal cord with other parts of the body. The brain communicates with most of the body through the spinal nerves. There are 31 pairs of them, located at intervals along the length of the spinal cord (see Overview of Spinal Cord Disorders ). Several cranial nerves and most spinal nerves are involved in both the somatic and autonomic parts of the peripheral nervous system. Spinal nerves emerge from the spinal cord through spaces between the vertebrae. Each nerve emerges as 2 short branches (called spinal nerve roots): one at the front of the spinal cord and one at the back. Motor nerve root (anterior nerve root):The motor root emerges from the front of the spinal cord. Motor nerve fibers carry commands from the brain and spinal cord to other parts of the body, particularly to skeletal muscles. Sensory nerve root (posterior nerve root):The sensory root enters the back of the spinal cord. Sensory nerve fibers carry sensory information (about body position, light, touch, temperature, and pain) to the brain from other parts of the body. The sensory nerve fibers in each sensory nerve root carry information from a specific area of the body, called a dermatome (see figure). After leaving the spinal cord, the corresponding motor and sensory nerve roots join to form a single spinal nerve. Some of the spinal nerves form networks of interwoven nerves, called nerve plexuses. In a plexus, nerve fibers from different spinal nerves are sorted and recombined so that all fibers going to or coming from one area of a specific body part are put together into one nerve (see figure). There are 2 major nerve plexuses: Brachial plexus:Sorts and recombines nerve fibers traveling to the arms and hands Lumbosacral plexus:Sorts and recombines nerve fibers going to the legs and feet 