Topics:
Animal Physiology, Animal Refresher
Main Function of Aldosterone
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Question (English)
Main function of aldosterone is-
- Na⁺ reabsorption & K⁺ secretion by collecting tubules ✓ Correct
- K⁺ reabsorption & Na⁺ secretion by collecting tubules
- Na⁺ reabsorption & K⁺ reabsorption by collecting tubules
- None
Explanation:
Correct Answer: Na⁺ reabsorption & K⁺ secretion by collecting tubules
Aldosterone (mineralocorticoid from adrenal cortex zona glomerulosa) acts on principal cells of collecting tubules (and late DCT) to promote Na⁺ reabsorption and K⁺ secretion (along with H⁺ secretion).
Mechanism
- Aldosterone binds intracellular mineralocorticoid receptor → enters nucleus → transcription of Na⁺/K⁺-ATPase and ENaC (epithelial Na⁺ channel) genes
- ENaC on apical membrane: Na⁺ enters from tubular fluid → K⁺ pumped out into lumen via ROMK channels
- Net: Na⁺ (+ water) retained → blood volume and pressure ↑; K⁺ and H⁺ excreted in urine
Stimuli for Aldosterone Release
- Decreased blood volume (primary stimulus → via Angiotensin II)
- Increased plasma K⁺
- Angiotensin II (from RAAS)
Electrolyte Regulation
- Na⁺ in ECF: regulated by Osmoreceptor–ADH–Thirst system
- K⁺ in ECF: regulated by Aldosterone
- Ca²⁺: regulated by PTH and Calcitonin
📚 About this Topic — Animal Physiology
This multiple choice question is from Animal Physiology, Animal Refresher. It has 4 options with a detailed explanation of the correct answer. Practice more MCQs from Animal Physiology to strengthen your preparation.
