Q. What are the hormones secreted by the adrenal medulla? What are their respective functions?
The medullary portion of the adrenals secretes hormones of the catecholamine group: noradrenaline (also known as norepinephrine) and adrenaline (also known as epinephrine). Besides their hormonal function noradrenaline and adrenaline act as neurotransmitters too and the neurons that use them as neurotransmitters are called adrenergic neurons.
Adrenaline increases the glycogen breaking into glucose (glycogenolysis) thus increasing the basal metabolic rate of the body and glycemia. Noradrenaline and Adrenaline are released during situations of danger (flight response or fightfight) and they intensify the strength and rate of the heartbeat and selectively modulate the blood irrigation in some tissues by selective vasoconstriction and selective vasodilation. By vasodilation they increase the blood supply to the brain, the muscles and the heart and by vasoconstriction they reduce the blood supply to the skin, the kidneys and the gastrointestinal tract.
Substances like noradrenaline and adrenaline that promote vasoconstriction or vasodilation are called vasoactive substances.