< b>Adrenal gland: One of a pair of small glands, each of which sits on top
of one of the kidneys. The adrenal is made up of an outer wall (the cortex) and
an inner portion (the medulla).
The adrenal glands produce hormones that help control the heart rate, blood pressure,
the way the body uses food, and other vital functions. The adrenal cortex secretes
steroid (cortisone-related) hormones and mineralocortoids that regulate the levels
of minerals such as sodium and potassium in the blood.
The adrenal medulla makes adrenaline (adrenaline) and noradrenaline (noradrenaline).
Adrenaline is secreted in response to low blood levels of glucose as well as exercise
and stress; it causes the breakdown of the storage product glycogen to the sugar
glucose in the liver, facilitates the release of fatty acids from adipose (fat)
tissue, causes dilation (widening) of the small arteries within muscle and increases
the output of the heart. Noradrenaline is a neurohormone, a neurotransmitter, for
of most of the so-called sympathetic nervous system.
The name "adrenal" comes from the Latin "ad-", toward + "rebes", kidney. It refers
to the perch of this gland atop the kidney. The adrenals are also called the suprarenal
glands, "supra-" in Latin meaning "on top."
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