The human nervous system has two major divisions, the voluntary and the autonomic systems. The voluntary system is concerned mainly with movement and sensation. It consists of a motor and sensory nerves, among many others.
The autonomic system mainly controls functions over which we have less conscious control. These include the digestion of food, blood pressure, and heart rate. Its nerves leave the spine and connect to all the major organs and glands, either inhibiting or stimulating their activity.