Question:medium
How does the kidney respond to shock?
How does the kidney respond to shock?
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The kidney actively constricts a glomerular inflow vessel to defend pressure.
Updated On: Jun 24, 2026
- Decreases renal blood flow
- Increases afferent arteriole resistance
- GFR remains unaltered
- Perfusion of the kidney increases
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The Correct Option is B
Solution and Explanation
Step 1: Frame the question as what the kidney actively does, not merely what happens to it, when systemic pressure drops. Step 2: Sensing reduced volume, the kidney drives vasoconstriction of the afferent arteriole, so afferent resistance $R_{aff}$ rises. Step 3: Because glomerular filtration depends on the pressure gradient across this vessel, raising $R_{aff}$ lowers glomerular capillary pressure and hence GFR; simultaneously aldosterone and ADH conserve sodium and water. Step 4: Thus saying renal blood flow simply decreases or perfusion increases or GFR is unchanged all miss the active regulatory step, which is the rise in afferent arteriolar resistance.\[\boxed{\text{Increases afferent arteriole resistance}}\]
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