Consists of the brain, spinal cord, and peripheral nerves, each performing specific functions. The processing of nerve impulses in the brain is somewhat localized. Basic functions are mediated in the lower parts of the brain, activities such as hunger, thirst, and thermoregulation. Sensory regions of the brain are located above, along with most voluntary control of muscles. The highest regions of the brain are dedicated to processing and integrating information, and the production of thought. The spinal cord is the primary pathway by which most of the nerve impulses are carried to the brain. Nerves throughout the body send pulses through the spinal cord to the brain where they are processed, and the brain sends back impulses to regulate and control organs and muscles. There are two main divisions to the nervous system: the central (brain and spinal cord) and the peripheral (nerves and ganglia located outside of the central nervous system). The peripheral nervous system is further divided into the somatic (voluntary muscular movements) and autonomic branches (various unconscious functions such as digestion, sweating, heart rate, pupillary response, vasomotor activity, etc.) Some taxonomies also add a third branch, the sensory nervous system. In polygraphy, the autonomic branch receives special attention due to its association with the physiological data recorded and analyzed with the polygraph.
