The Autonomic Nervous System (ANS) regulates involuntary functions of smooth muscle (e.g. in blood vessels, gut), cardiac muscle (heart rate), and glands (secretion). The ANS has two divisions: sympathetic (fight-or-flight: increases heart rate, dilates pupils, inhibits digestion) and parasympathetic (rest-and-digest: decreases heart rate, stimulates digestion). Both divisions of the ANS collectively control these involuntary effectors.