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adrenal medulla

The adrenal medulla is the central, reddish-brown portion of the adrenal gland and is surrounded by the adrenal cortex. It consists of irregularly shaped cells grouped around blood vessels, which are intimately connected by the sympathetic division of the autonomic nervous system. The cells of the adrenal medulla produce, store, and release epinephrine (adrenaline), norepinephrine (noradrenaline), and a small amount of dopamine. These are the hormones involved in the fight-or-flight response, where the production of epinephrine increases heart rate and blood pressure, blood vessel constriction in the skin and gastrointestinal tract, smooth muscle dilation, and metabolism; norepinephrine has the opposite effect.