The PNS is divided into a) somatic and b) autonomic nervous system, and c) the enteric nervous system. Somatic nerves mediate voluntary movement. The autonomic nervous system) is the one that influences the function of internal organs, it is further subdivided into the sympathetic and the parasympathetic nervous systems. The sympathetic nervous system is activated in cases of emergencies to mobilize energy, while the parasympathetic nervous system is activated when organisms are in a relaxed state. The enteric nervous system functions to control the gastrointestinal system. Both autonomic and enteric nervous systems function involuntarily. Nerves that exit from the cranium are called cranial nerves while those exiting from the spinal cord are called spinal nerves.