Adrenaline (also called epinephrine), along with noradrenaline (norepinephrine) and dopamine, are catecholamines (substances containing a dihydroxy phenyl grouping with the hydroxy groups in adjacent positions). All three are released at some nerve terminals to act as neurotransmitters, but adrenaline is also found in the adrenal medulla and in chromaffin cells and can be released from these sites into the circulating blood to have effects throughout the body. Adrenaline is synthesized in the adrenal medulla by the methylation of noradrenaline, and both compounds are released from the gland together. Release of adrenal medullary catecholamines is caused by stressful stimuli, acting via the sympathetic nervous system in the so-called flight, fright, and fight phenomenon. Release of adrenaline prepares the individual to deal with the stress; heart rate and force are increased, blood pressure rises, and blood flow to the skeletal and cardiac muscles is increased, while blood flow to the less essential areas (e.g. gut, skin) is decreased. Adrenaline also mobilizes glycogen energy stores from the liver to increase blood glucose.
— Alan W. Cuthbert.
See also adrenal glands; autonomic nervous system.






