/ep'euh nef"rin, -reen/, n.1. Biochem. a hormone secreted by the adrenal medulla upon stimulation by the central nervous system in response to stress, as anger or fear, and acting to increase heart rate, blood pressure, cardiac output, and carbohydrate metabolism.2. Pharm. a commercial form of this substance, extracted from the adrenal glands of sheep and cattle, or synthesized: used chiefly as a heart stimulant, to constrict the blood vessels, and to relax the bronchi in asthma.Also, epinephrin. Also called adrenaline.[1895-1900; EPI- + Gk nephr(ós) kidney + -INE2]
* * *or adrenalineOne of two hormones (the other being norepinephrine) secreted by the adrenal glands, as well as at some nerve endings (see neuron), where they serve as neurotransmitters.They are similar chemically and have similar actions on the body. They increase the rate and force of heart contractions, increasing blood output and raising blood pressure. Epinephrine also stimulates breakdown of glycogen to glucose in the liver, raising blood glucose levels, and both hormones increase the level of circulating free fatty acids. All these actions ready the body for action in times of stress or danger, times requiring increased alertness or exertion. Epinephrine is used in medical situations including cardiac arrest, asthma, and acute allergic reaction (see allergy). See also dopamine.
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