The Definition Of the Autonomic Nervous System

Definition: The autonomic nervous system (ANS) is the part of the nervous system in charge of regulating involuntary vital functions, including the activity of the heart, the digestive system and the glands. It’s divided into two subsystems: the sympathetic nervous system, which responds to stress by speeding the heart rate, constricting blood vessels, decreasing digestive activity, raising blood pressure, and preparing the body to fight or run (the fight-or-flight response response); and the parasympathetic nervous system, which counteracts this response by slowing heart rate, increasing digestive and gland activity and relaxing muscles.