Question

Kidney responds to shock by

• A. Decreases renal blood flow
• B. Increases afferent arteriole resistance
• C. GFR remains unaltered
• D. Perfusion of kidney increases

Answer 1

The Correct Option is B

Step 1: Picture the kidney during circulatory shock. Effective blood volume is low, so neurohormonal systems (sympathetic drive, renin-angiotensin, ADH, aldosterone) switch on to defend pressure and conserve fluid.
Step 2: A key part of this defence is constriction of the renal arterioles. Raising resistance at the afferent arteriole is the active vascular response the kidney uses, which corresponds to the option increases afferent arteriole resistance.
Step 3: Trace the consequences to rule out the distractors. Because the arterioles constrict, the glomerular filtration rate falls rather than staying the same, so $GFR$ unaltered is false. Overall renal perfusion goes down, not up, so increased perfusion is false.
Step 4: While it is true that renal blood flow drops in shock, the option that names the underlying active mechanism is the rise in afferent arteriolar resistance, which is the response being asked for.
Hence the kidney responds to shock by increasing afferent arteriole resistance.\[\boxed{\text{Increases afferent arteriole resistance}}\]