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Question #45747
The Question
During severe autonomic dysregulation, such as a catecholamine storm experienced in drug withdrawal syndrome, a patient exhibits a marked inability to produce highly concentrated urine despite systemic dehydration. Based on the principles of renal hemodynamics and the counter-current mechanism, which of the following physiological cascades best explains this anomaly?
Options
- A.
Sympathetic overactivation causes vasodilation of the vasa recta, leading to the rapid washout of NaCl and urea from the medullary interstitium.
- B.
Intense vasoconstriction of afferent arterioles drastically reduces GFR and filtrate flow, compromising the dynamic urea recycling and NaCl transport needed to maintain the corticomedullary gradient.
- C.
The adrenergic surge directly inhibits the active transport of Na+ and Cl- in the descending limb of the Loop of Henle, halting the multiplier effect.
- D.
Decreased renal blood flow stimulates excessive renin release, which directly blocks the permeability of the collecting duct to urea.
Check Your Answer
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
Renal_Blood_Flow|Glomerular_Filtration_Fraction|Adrenergic_Influence
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Students often memorize the oversimplified rule that 'low GFR = more time for reabsorption = concentrated urine' (true for mild volume depletion).
However, they fail to synthesize that the counter-current multiplier is a highly dynamic system.
A severe, pathological drop in GFR (as in an autonomic storm) disrupts the mass delivery of solutes (NaCl and urea) to the medullary interstitium, effectively collapsing the osmotic gradient required for water extraction in the collecting duct.
The question also utilizes a high-frequency NEET location trap regarding the specific permeabilities of the descending versus ascending limbs of the Loop of Henle.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Excretory Products and Their Elimination - Class 11 |
| Concept | Urea Recycling |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |