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Introduction: Each adrenal gland is, in effect, structurally and functionally two endocrine glands in one in that it is comprised of an outer cortex surrounding an inner medulla. The cortex contains three histologically distinct zones from out to inward. These are the zona glomerulosa, zona fasciculata, and zona reticularis.
These are synthesized in the same cells. However, once secreted they interact with four adrenergic receptors such as 1, 2, 1, 2, and 3 that mediate the cellular effects of the hormones. Stress the predominant stimulus that leads to secretion of these hormones. More accurately stimuli such as injury, anger, pain, cold, strenuous exercise, and hypoglycemia as a result of stress response generate sympathetic impulses in the cholinergic preganglionic fibers that provides the neural impetus to the chromaffin cells, and this ultimately culminates into the release of catecholamines. Biochemically, however, catecholamines stimulate glucose production in the liver, lipolysis in the adipose tissue, and promotes anaerobic metabolism in the muscles leading to lactate production. Whereas, the adrenal medulla responds to predominantly neural stimuli, the outer adrenal cortex that literally encapsulates the medulla and forms the bulk of the gland, responds only to endocrine stimulation and releases a number of hormones which have steroid structures chemically. These hormones are glucocorticoids, aldosterone, and adrenal androgens. ...
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