The central nervous system includes the brain and spinal cord. The peripheral nervous system includes all of the nerves carrying signals to and from the brain and spinal cord. The Sympathetic and Parasympathetic Nerves Parasympathetic nerves tend to slow down body activity when the body is not under stress. The spinal cord is a pathway for signals traveling between the peripheral nervous system and the brain. The cord is also the center for controlling some reflex actions.
Signals move up and down the spinal cord in bundles of sheathed axons.
The tracts located on the periphery of the spinal cord glisten because of their myelin sheaths and are called white matter. The body's master control panel, the brain, is a continuation of the anterior end of the spinal cord. The brain is protected by meninges and bones. The most primitive tissue is the brain stem, which contains simple, basic reflex centers. The cerebellum acts as a reflex center for maintaining posture and coordinating limbs.