Epinephrine

epinephrine, also called adrenaline, hormone that is secreted mainly by the medulla of the adrenal glands and that functions primarily to increase cardiac output and to raise glucose levels in the blood. Epinephrine typically is released during acute stress, and its stimulatory effects fortify and prepare an individual for either “fight or flight” (see fight-or-flight response). Epinephrine is closely related in structure to norepinephrine, differing only in the presence of a methyl group on the nitrogen side chain. In both substances, the amine (nitrogen-containing) group is attached to a catechol group (a benzene ring with two hydroxyl groups)—a structure unique to the catecholamines. Both substances are key stimulatory components of the sympathetic nervous system (part of the autonomic nervous system), hence their pharmacological classification as sympathomimetic agents.