Adrenal medulla
The adrenal medulla is a hormone-producing organ within the adrenal gland formed primarily of chromaffin cells. The medulla is innervated by preganglionic sympathetic fibers descending from the brain as a regulatory pathway in the sympathetic nervous system. The adrenal medulla is the site of adrenaline releases in a fight-or-flight response.
The adrenal medulla takes up the core 20 percent of the adrenal gland. It secretes two catecholamine hormones into the blood: epinephrine (adrenaline) and norepinephrine (noradrenaline). Of catecholamines produced in the adrenal medulla about 80 percent are epinephrine and 20 percent are norepinephrine.
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