Topics:
Animal Physiology, Animal Refresher
Major Stimulus for Aldosterone Release
The major stimulus for release of aldosterone is:
- Decreased blood volume — Correct Answer
- Decreased blood osmolarity
- Increase K⁺
- Decrease Na⁺
Explanation:
Correct Answer: Decreased blood volume
The major stimulus for aldosterone release from the adrenal cortex (zona glomerulosa) is decreased blood volume, acting primarily through the Renin-Angiotensin-Aldosterone System (RAAS).
RAAS Pathway
- Decreased blood volume / decreased blood pressure → JG cells of kidney release Renin.
- Renin converts Angiotensinogen → Angiotensin-I.
- ACE (Angiotensin-Converting Enzyme, in lungs) converts Angiotensin-I → Angiotensin-II.
- Angiotensin-II stimulates adrenal cortex → releases Aldosterone.
Actions of Aldosterone
- Acts on collecting duct/DCT → Na⁺ reabsorption & K⁺ secretion.
- Water follows Na⁺ → blood volume increases → blood pressure rises.
Other Stimuli for Aldosterone Release
- Hyperkalemia (increased K⁺ in blood) — direct stimulant of aldosterone (independent of RAAS).
- Hyponatremia (decreased Na⁺) — minor direct stimulus.
- ACTH (adrenocorticotropic hormone) from pituitary — minor stimulus.
Aldosterone Antagonist
- ANP (Atrial Natriuretic Peptide) opposes aldosterone — released when blood volume is too high → promotes Na⁺ and water excretion → lowers blood volume and BP.
📚 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.
