Before You Begin
Question #45719
The Question
The counter-current mechanism relies on the precise cycling of NaCl and urea to maintain the medullary osmotic gradient. If a patient develops a lesion completely destroying the supraoptic and paraventricular nuclei of the hypothalamus, which of the following represents an INCORRECT physiological consequence?
Options
- A.
The inner medullary collecting duct loses its permeability to urea, impairing urea recycling into the interstitium.
- B.
The active transport of NaCl from the thick ascending limb of Henle's loop into the medullary interstitium is halted.
- C.
The peak osmolarity of the inner medullary interstitium fails to reach the maximum of 1200 mOsmol/L.
- D.
The tubular fluid passing through the distal convoluted tubule and collecting duct remains hypotonic.
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
Collecting_duct|Hypothalamo-Hypophyseal_Portal_System|Osmoreceptors
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Students often assume that a failure in the urine concentrating mechanism (lack of ADH) shuts down the entire counter-current multiplier.
The trap lies in distinguishing between ADH-dependent processes (urea recycling and facultative water reabsorption) and ADH-independent processes (active NaCl transport in the thick ascending limb).
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Excretory Products and Their Elimination - Class 11 |
| Concept | Counter-Current Exchanger |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |