alleryStart learning →What happens to potassium when the nephron reabsorbs more sodium?
AMore potassium is reabsorbed alongside it
BMore potassium is secreted into the lumen
CPotassium handling does not change at all
DPotassium is filtered at a lower rate
Answer & Solution
Correct answer: B. More potassium is secreted into the lumen
1. Sodium and potassium concentrations move in opposite directions in the nephron.
2. When more sodium is reabsorbed, more potassium is secreted into the lumen.
3. When less sodium is reabsorbed, more potassium is retained in the circulation.
4. Aldosterone drives this pairing, since recovering sodium leaves a negative gradient that promotes potassium and chloride secretion.
5. Treating the two ions as independent would make the effects of aldosterone impossible to predict.
_Source: OpenStax Anatomy and Physiology (CC BY 4.0), Ch 25 "The Urinary System", section 25.9 Regulation of Fluid Volume and Composition_
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