5.2 Hormonal Control of Excretory System
Module 8 ~ Lesson 5
Water intoxication is an interesting example of how your body can react to imbalance. Water intoxication occurs when the normal balance of electrolytes in the body become severely altered due to an excess of water consumption.
The concentration gradient between ions such as sodium and outside cells is lowered. Osmotic pressure is reversed, and water moves into the cells in an effort to balance concentration. Electrolyte imbalance and tissue swelling can cause fluid in the lungs and an irregular heartbeat. Swelling puts pressure on the brain and nerves, which can produce behaviour resembling alcohol intoxication.
Instances of water intoxication are much less common than the opposite extreme, dehydration. Your body has a mechanism to respond to high osmotic pressure in your bloodstream that occurs under dehydrated conditions. High osmotic pressure occurs when there are low water and high solute (salt) concentrations.
When blood pressure drops or sodium ion concentration in the blood is reduced, it stimulates the release of aldosterone from a triangular-shaped gland located on top of each kidney. Aldosterone stimulates the distal tubules and collecting ducts to reabsorb sodium ions. Negatively charged chlorine ions and water are also reabsorbed, which has the net effect of retaining salt and water. Aldosterone also stimulates the secretion of potassium ions into the distal tubes and collecting ducts if the concentration of potassium ions in the blood is high.
ReadRead "Regulating Reabsorption of Water", "Reabsorption of Salts", "Maintaining the Blood pH", and "Upsetting the Balance of the Excretory System" on pages 316 to 318 of your textbook.