epinephrine

n. Ahormone (C₉H₁₃NO₃) and neurotransmitter created in the adrenal glands which acts primarily as an arousal agent. Epinephrine causes an increase in heart rate and heart stroke volume, dilates the pupils, increases blood sugar levels, reduces blood flow to the skin and digestive tract, increases blood flow to the muscles, and suppresses immune function. It is used to stimulate the heart in cases of cardiac arrest and sometimes in cardiac arrhythmias. Epinephrine is one of the main neurotransmitters in the flight-or-fight response and in activating the reticular activating system (RAS). Its action is mimicked by amphetamines, caffeine, and Ritalin. Also called adrenaline.