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Question #45712
The Question
A patient suffers severe hemorrhage leading to hypovolemic shock, resulting in a hyper-activation of the RAAS mechanism and peak secretion of ADH. Despite maximum ADH levels, the ability of the kidneys to concentrate urine to 1200 mOsmol/L is threatened. Which of the following best explains this physiological paradox?
Options
- A.
The medullary interstitial osmolarity will exceed 1200 mOsmol/L due to the synergistic hyper-activation of Aldosterone and ADH, causing receptor downregulation.
- B.
The efficiency of the counter-current multiplier decreases due to a drastic fall in GFR, reducing NaCl delivery to the thick ascending limb of the Loop of Henle.
- C.
The vasa recta actively transports NaCl out of the medullary interstitium to compensate for the reduced tubular flow, washing out the gradient.
- D.
ADH independently maintains the medullary gradient by maximizing urea recycling, but the collecting duct becomes impermeable to water under severe hypoxia.
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Correct Answer
Step-by-Step Solution
Explanation
How the Examiner Thinks
Regulatory_Failure
Understand how NOT, EXCEPT, and logical constraints are used to manipulate exam results.
Concepts Behind This Question
Loop of Henle|ADH (Vasopressin) Logic|RAAS Mechanism
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Students often memorize the oversimplified rule that 'High ADH = Maximum Urine Concentration (1200 mOsmol/L)'.
This question tests the deeper NCERT concept that ADH only provides the permeability for water reabsorption in the collecting duct.
The actual driving force (the osmotic gradient) is created by the Counter-Current Multiplier.
If GFR drops severely, the multiplier lacks the NaCl delivery required to build the gradient, meaning ADH has a weaker gradient to work with, exposing a critical 'perfusion-concentration' paradox.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Excretory Products and Their Elimination - Class 11 |
| Concept | Counter-Current Mechanism Multiplier |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |