Adrenal gland

In mammals, the adrenal glands (also known as suprarenal glands or colloquially as kidney hats) are the triangle-shaped endocrine glands that sit atop the kidneys; their name indicates that position (ad, "near" or "at" + renes, "kidneys"). They are chiefly responsible for regulating the stress response through the synthesis of corticosteroids and catecholamines, including cortisol and adrenalin.

Adrenal medulla

Composed mainly of hormone-producing chromaffin cells, the adrenal medulla is the principal site of the conversion of the amino acid tyrosine into the catecholamines epinephrine and norepinephrine (also called adrenaline and noradrenaline, respectively). Medullary cells are derived from the embryonic neural crest and, as such, are simply modified neurons. In particular, they are postganglionic cells of the sympathetic nervous system, receiving innervation from corresponding preganglionic fibers. Moreover, as the synapses between pre- and postganglionic fibers are called ganglia, the adrenal medulla is actually a ganglion of the sympathetic nervous system.

Related Topics:
Chromaffin cell - Amino acid - Tyrosine - Epinephrine - Norepinephrine - Embryo - Neural crest - Neuron - Postganglionic cell - Sympathetic nervous system - Preganglionic fiber - Ganglia

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

In response to stressors such as exercise or imminent danger, medullary cells release catecholamines into the blood in a 70:30 ratio of epinephrine to norepinephrine. Notable effects of epinephrine and norepinephrine include increased heart rate, blood vessel constriction, bronchiole dilation, and increased metabolism, all of which are characteristic of the fight-or-flight response.

Related Topics:
Stressor - Exercise - Heart rate - Blood vessel constriction - Bronchiole - Metabolism - Fight-or-flight response

~ ~ ~ ~ ~ ~ ~ ~ ~ ~