Adrenaline, also known as epinephrine, is primarily a hormone. The amino acids phenylalanine and tyrosine are precursors to noradrenaline, which is then converted into adrenaline in the adrenal medulla (part of the adrenal glands). Small amounts are also produced in nerve cells throughout the body and can act as a neurotransmitter. During times of stress the sympathetic nervous system triggers adrenaline to be released by the adrenal medulla into the bloodstream. This triggers the body’s “fight or flight” response, increasing heart rate and blood pressure; expanding air passages in the lungs; enlarging pupils; redistributing blood to the muscles and slowing digestion and other non-essential bodily functions.You and Your Hormones from the Society for Endocrinology. (2018). Adrenaline. [online] Available at: http://www.yourhormones.info/hormones/adrenaline/ [Accessed 15 Nov. 2018]. Drugs.com. (2016). Norepinephrine vs Epinephrine: What’s the difference?. [online] Available at: https://www.drugs.com/answers/norepinephrine-epinephrine-difference-3132946.html [Accessed 29 Nov. 2018].