The nervous system comprises the central nervous system (CNS) and the peripheral nervous system (PNS) components. The peripheral nervous system (PNS) is composted of three parts: the somatic, autonomic and enteric. The somatic portion functions to control voluntary movement, while the autonomic and enteric function involuntarily to control various bodily functions. The autonomic nervous system (ANS) controls homeostasis of the entire body, which includes the cardiovascular activity, digestion, urination, sexual function, sweating, sleep, and ability to maintain upright position.  Many physicians, including ourselves, consider the enteric nervous system (ENS) as actually a part of the ANS, and it is the most independent functioning of the components of the ANS. It controls gastrointestinal function (secretion and peristalsis).