The two adrenal glands are small, triangular structures situated on the upper portion of each kidney just below the diaphragm. They are composed of two portion, called the adrenal medulla; and the outer portion, called the cortex. Each portion has a separate secretion and function. Epinephrine and norepinephrine are secreted into the blood stream by the medullary portion. This medullary portion of the gland is derived from the same embryonic cells that form the sympathetic nervous system. Fear, anger, excitement, sudden physical exertion are some of the stimulating factors, both to the sympathetic nervous system, and, in turn, to the secretion of epinephrine.
Adrenaline is the trade name for epinephrine. On the other hand norepinephrine serves as an effective aide to epinephrine, causing an increase in the rate of heartbeat and constricting the skin capillaries so that blood is forced out of them and shunted, by the action of the epinephrine to the body’s major organs.
A number of hormones which may be divided into four groups: Mineralocorticoids or Aldosterone which promotes retention of sodium and water in the body effecting blood pressure, glucocorticoids hydrocortisone which acts to raise blood glucose levels and as an anti-inflammatory agent, steroids, related to sex hormones. See diagram.
Response of Body Stress
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The presence of intact adrenal cortices appears to be essential to enable animals to react to environmental change, and it has lately been suggested that in man exposure to continued environmental stress may bring about functional and morphological changes in the adrenal cortex which may form the basis for the so-called stress diseases.
In Addison’s disease, progressive destruction of the cortex of the adrenal, usually as the result of tuberculosis gives rise to symptoms resulting from deficiencies of the hormones listed above. In the Waterhouse-Friderichsen syndrome, destruction of part or the whole of one or both glands by hemorrhage occurring in the course of meningitis due to meningococci leads to sudden collapse and death unless very prompt treatment by replacement of the absent hormones is available. The most common cause of Addison’s disease is pituitary tumor.
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