Q.Aldosterone acts at the distal convoluted tubule and collecting duct resulting in the absorption of water through
a. Aquaporins
b. spectrins
c. GLUT
d. Chloride channels

Why Does the Kidney Need Regulation?

Your body is a bag of water with salt dissolved in it. Every day, you drink, you sweat, you breathe out moisture, and you eat salty food. Left to itself, the composition of your blood would swing wildly — too dilute after a big glass of water, too concentrated after a sweaty run. The kidney's job is to hold the line: keep the volume of blood steady and the concentration of salts (especially sodium) within a razor-thin range.

But the kidney can't just guess. It needs signals — hormones — that tell it: "We're getting dehydrated, hold onto water" or "Blood pressure is dropping, save salt" or "We've had enough, flush it out." That's regulation.

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The Three Main Controllers

Three hormone systems work together, like a thermostat with multiple sensors. They act on the nephron — specifically on the distal convoluted tubule and the collecting duct, where the final adjustments to urine are made.

1. ADH (Antidiuretic Hormone) — The Water Saver

Intuition: Imagine you're in a desert with limited water. Your brain detects that blood is getting too concentrated (osmoreceptors in the hypothalamus fire). It sends a signal: "Release ADH." ADH travels in the blood to the kidney and tells the collecting duct: "Open the water channels (aquaporins)." Water rushes out of the tubule back into the blood. You produce a small volume of concentrated urine.

If you've just drunk a litre of water, ADH secretion stops. The collecting duct becomes waterproof. Water stays in the tubule and leaves as dilute urine. …