Adrenal medulla hormones

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:
 * adrenaline (epinephrine),
 * noradrenaline (norepinephrine), and
 * dopamine.

In response to stressors such as exercise or imminent danger, medullary cells release catecholamines into the blood in a 85:15 ratio of adrenaline to noradrenaline.

Notable effects of adrenaline and noradrenaline include increased heart rate and blood pressure, blood vessel constriction, bronchiole dilation, and increased metabolism, all of which are characteristic of the fight-or-flight response. Release of catecholamines is stimualted by nerve impulses, and receptors for catecholamines are widely distributed throughout the body.

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