adrenaline

adrenalin (adrenaline, epinephrine) A hormone secreted by the adrenal medulla and largely responsible for the ‘fight or flight’ response in mammals. It stimulates the breakdown of glycogen, thus raising the blood-sugar level, it mobilizes free fatty acids, and it has a variety of effects on the cardiovascular and muscular systems.

adrenaline Hormone secreted by the adrenal glands, important in preparing the body's response to stress. It has widespread effects in the body, increasing the strength and rate of heartbeat and the rate and depth of breathing, diverting blood from the skin and digestive system to the heart and muscles, and stimulating the release of glucose from the liver to increase energy supply by promoting increased respiration. Synthetic adrenaline is used medicinally in the resuscitation of patients in shock or following cardiac arrest.

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.