Epinephrine, otherwise known as adrenaline, is a hormone secreted by the adrenal glands that is involved in the "fight or flight" response in humans. This response occurs when an individual comes in contact with a threat causing the body to release epinephrine giving the individual energy to respond to the threat.
Epinephrine is derived from tyrosine, one of the 20 major amino acids.
Cashin-Garbutt, April. "What is Epinephrine (Adrenaline)?." News Medical. N.p., n.d. Web. 6 Dec. 2012. <http://www.news-medical.net/health/What-is-Epinephrine-(Adrenaline).aspx>.