adrenaline (also called epinephrine)

one of two chemicals (the other is norepinephrine) released by the adrenal gland that increases the speed and force of heartbeats. It dilates the airways to improve breathing and narrows blood vessels in the skin and intestine so that an increased flow of blood reaches the muscles and allows them to cope with the demands of exercise. It is also a drug that can be given in anaphylactic emergencies.