Question

Aldosterone from adrenal cortex stimulates the reabsorption of water and Na$^+$ from ________.

• A. Proximal Convoluted Tubule (PCT)
• B. Ascending limb of loop of Henle
• C. Distal Convoluted Tubule (DCT)
• D. Descending limb of loop of Henle

Hint:

Remember the RAAS mechanism. Aldosterone facilitates the conditional reabsorption of Na$^+$ and water specifically in the DCT.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept: Aldosterone is a mineralocorticoid hormone secreted by the adrenal cortex that regulates blood pressure, sodium, and potassium levels in the blood.
Step 2: Key Formula or Approach: Identify the specific target site (segment of the nephron) where aldosterone exerts its primary physiological effect.
Step 3: Detailed Explanation: Aldosterone acts primarily on the later parts of the nephron, specifically the Distal Convoluted Tubule (DCT) and the collecting duct.
It stimulates the active "conditional" reabsorption of sodium ions (Na$^+$) and, consequently, water from the filtrate back into the blood plasma.
It also promotes the excretion of potassium (K$^+$) and phosphate ions into the urine.
The Proximal Convoluted Tubule (PCT) is responsible for bulk reabsorption, while the Loop of Henle is involved in creating a concentration gradient, but they are not the primary targets for aldosterone.
Step 4: Final Answer: The correct option is (3).