The adrenals function as several separate endocrine glands within one anatomical structure.
The adrenal medulla is an extension of the sympathetic nervous system which secretes catecholamines.
The adrenal cortex produces three major classes of steroids: (1) glucocorticoids, (2) mineralocorticoids, and (3) adrenal androgens.
Most of the adrenal cortex is made up of cells which secrete cortisol and adrenal androgens, and form part of the hypothalamic-pituitary-adrenal axis.
The small outer glomerulosa of the cortex secretes aldosterone under the control of the renin-angiotensin system.
-These functions are important in the integrated control of cardiovascular, metabolic and immune responses to stress.
The hypothalamic-pituitary-adrenal axis. The main sites for feedback control by plasma cortisol are the pituitary gland (1) and the hypothalamic corticotropin-releasing center (2). Feedback control by plasma cortisol also occurs at the locus coeruleus/sympathetic system (3) and may involve higher nerve centers (4) as well. There may also be a short feedback loop involving inhibition of corticotropin-releasing hormone (CRH) by adrenocorticotropic hormone (ACTH) (5). Hypothalamic neurotransmitters influence CRH release; serotoninergic and cholinergic systems stimulate the secretion of CRH and ACTH; adrenergic agonists and -aminobutyric acid (GABA) probably inhibit CRH release. The opioid peptides -endorphin and enkephalin inhibit, and vasopressin and angiotensin II augment, the secretion of CRH and ACTH. -LPT, -lipotropin; POMC, pro-opiomelanocortin; LC, locus coeruleus; NE, norepinephrine.
