Autonomic Nervous System (ANS):

Autonomic nervous system (ANS), also called visceral nervous system, is a component of the peripheral nervous system (PNS) made up of autonomic nerves that connect the spinal cord to the heart, stomach, intestines, and other visceral organs. The control and regulate involuntary physiologic processes, including heartrate, blood pressure, respiration, digestion, and sexual arousal. Also see the ANS’s three divisions:

• Sympathetic nervous system activates body processes that help in times of stress or danger, responsible for the body’s fight-or-flight response (FNR). (See my blog on anxiety for a detailed description of the FNR body process.)
• Parasympathetic nervous system, opposite of the sympathetic nervous system, is responsible for the “rest-and-digest” body processes, including the resting and “return-to-normal” phase of FNR.
• Enteric nervous system: Manages how the body digests food.