Epinephrine, also known as adrenalin or adrenaline, is a hormone, neurotransmitter, and medication. Epinephrine is normally produced by both the adrenal glands and certain neurons.

It plays an important role in the fight-or-flight response by increasing blood flow to muscles, output of the heart, pupil dilation, and blood sugar. It does this by binding to alpha and beta receptors. It is found in many animals and some single cell organisms. Napoleon Cybulski first isolated epinephrine in 1895.

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