Introduction to autonomic pharmacology—the nervous system is divided into central and peripheral nervous systems. The peripheral nervous system consists of autonomic and somatic nervous system. The autonomic nervous system is not under voluntary control and consists of two major divisions—the sympathetic and the parasympathetic. The two divisions have opposing effects and normally their effects are in a state of equilibrium. The prime function of the sympathetic system is to help a person to adjust to stress and prepare the body for fight or flight reactions while parasympathetic system takes part in tissue building reactions. In the ANS, the neurotransmitters released are acetylcholine, noradrenaline, dopamine, and in adrenal medulla, it is adrenaline and noradrenaline.