Module 2 Lesson 5 - 5
Lesson 5 — The Adrenal Gland
Aldosterone
Read pages 317 and 454
A second group of hormones produced by the adrenal cortex is called the mineralocorticoids, which includes aldosterone.
Aldosterone increases reabsorption of sodium ions into the blood from the kidneys. This causes an increase in solute concentration of the blood, which results in water reabsorption. The difference between aldosterone and antidiuretic hormone (ADH) is that ADH increases directly the permeability of cells in the nephrons of the kidneys to reabsorb more water and aldosterone does that indirectly through absorption of sodium ions.
Reabsorption of sodium ions is very important because sodium ions are essential in nerve impulse transmission (studied in Module 1), muscle contraction, and ion (electrolyte) balance in the body.
Aldosterone helps the body cope with an ongoing stressful situation by targeting the kidneys where it promotes the renal absorption of sodium ions into the bloodstream. The increase in the solute concentration of the blood that results draws more water from the nephrons in the kidneys, resulting in higher blood pressure. Higher blood pressure is advantageous as a stress response because more oxygen and glucose from the blood are made available to the tissues in less time.
This response is different from the "fight-or-flight" response in that it occurs over a much longer time than the "fight-or-flight" response does, and it may be harmful to the circulatory system if sustained for long periods, resulting in increased risk of heart attack and atherosclerosis.
Disorders Related to Adrenal Glands
The appropriate level of hormones circulating in the body is critical to proper homeostasis. Too much cortisol and aldosterone cause a person to develop Cushing's disease. Too little of these hormones and a person develops Addison's disease.
Contrasting Over-secretion and Under-secretion of Adrenal Cortex Hormones
| Features | Cushing's Disease | Addison's Disease |
| Hormones Involved | Cortisol, aldosterone | Cortisol, aldosterone |
| Level of Hormones Secreted | Too much | Too little |
| Cause of Inappropriate Level of Secretion | Tumors in anterior pituitary causing over-secretion of ACTH OR tumors in adrenal cortex causing over-secretion of cortisol/aldosterone | Destruction of cells in adrenal cortex (autoimmune disease) |
| Symptoms | Excess accumulation of fat at back of neck (buffalo hump) or puffiness of the face causing a round or "moon" face due to water retention, increased blood pressure and decreased resistance to infections | Sodium ions not balanced, loss of water in urine, decreased blood pressure, low blood glucose, high potassium levels |
| Treatment | Surgery to remove or radiation to shrink tumors, drugs to dampen effect of ACTH | Cortisol in the form of prednisone or hydrocortisone by mouth in tablet form |
Did You Know?
Epinepherine auto-injector for allergic reaction contains epinephrine. Allergic reactions (from bee sting venom, peanuts, nuts, some medications etc.) cause the bronchioles to constrict.
Epinephrine restores breathing by dilating bronchioles. During cardiac arrest, epinephrine can stimulate the heart to start beating.
Adrenal Glands Overview
| adrenaline | mineralocorticoids - aldosterone | glucocorticoids - cortisol |
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| short-term response | long-term responses | long-term responses |