The parts of the body in charge of involuntary and voluntary actions. It consists of the brain and spinal cord, as well as the nerves, and it transmits signals throughout the body. The two main parts of the system are the central nervous system, or CNS (brain and spinal cord), and the peripheral nervous system, or PNS (nerves). The PNS consists of the somatic (voluntary), autonomic (sympathetic for emergencies and parasympathetic for relaxation), and enteric (gastrointestinal) nervous systems. Autonomic and enteric systems are involuntary.