AEMCA Practice Exam

How does aldosterone influence kidney function?

1. It decreases sodium reabsorption

2. It promotes calcium excretion

3. It increases sodium and water reabsorption

4. It reduces urine output

The correct answer is: It increases sodium and water reabsorption

Aldosterone is a steroid hormone produced by the adrenal glands that plays a crucial role in regulating sodium and potassium levels in the blood. Its primary function in the kidneys is to increase sodium reabsorption in the distal convoluted tubule and collecting duct of the nephron. When aldosterone acts on the kidneys, it stimulates the epithelial cells to increase the number and activity of sodium channels and sodium-potassium ATPase pumps. This results in greater reabsorption of sodium from the urine back into the bloodstream. As sodium is reabsorbed, water typically follows due to osmotic forces, leading to an increase in total blood volume. Consequently, this action not only increases sodium reabsorption but directly influences water retention as well. By promoting sodium and water reabsorption, aldosterone helps maintain blood pressure and electrolyte balance, which is essential for normal physiological functioning. Therefore, the correct understanding of aldosterone's role underscores the importance of sodium retention and the resultant impact on overall fluid balance in the body.