Adrenal Glands

The adrenal glands (suprarenal glands) curve over the top of each kidney in the abdomen. Although it appears to be one organ, it is actually two small glands, each weighing about 1/4 ounce (7 grams). The adrenal medulla (inner part or zona glomerulosa) is an agent of the sympathetic nervous system and is activated by nerve impulses. The adrenal cortex (the outer part, or zona fasciculata) is a true endocrine gland activated by adrenocorticotrophic hormone (ACTH) sent out from the pituitary gland.

The adrenal medulla secretes the catecholamines epinephrine and norepinepherine. These hormones help the body reduce stress. When the sympathetic nervous system reacts to intense emotions, such as fright or anger, large amounts of the hormone are released. This may cause a "fight or flight" reaction, in which blood pressure rises, the pupils widen, and blood is shunted to the most vital organs and to the skeletal muscles. The heart is also stimulated.

The adrenal cortex secretes two hormones: cortisol and aldosterone. These hormones are known collectively as corticosteroids. They help the body reduce stress and are essential for life. Cortisol is an energy generator. It regulates conversion of carbohydrates into glucose and directs reserves to the liver. It also suppresses inflammation. Aldosterone regulates the mineral and water balance of the body. It prevents excessive loss of water through the kidneys and maintains the balance between sodium and potassium in the blood stream. This balance is important to the contractility of muscles.

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