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Question #45734
The Question
Atrial Natriuretic Factor (ANF) acts as a crucial check on the Renin-Angiotensin-Aldosterone System (RAAS) by promoting vasodilation and increasing Glomerular Filtration Rate (GFR). In a clinical scenario, a patient with persistent hypervolemia and hypertension is found to have highly elevated ANF levels, indicating target-tissue resistance. Assuming the defect lies in the intracellular calcium dynamics of the Vascular Smooth Muscle Cells (VSMCs), which of the following cellular anomalies best explains this physiological failure?
Options
- A.
A defect in myofilament-associated proteins that maintains high Ca2+ sensitivity, preventing smooth muscle relaxation despite ANF signaling.
- B.
Enhanced active transport of Ca2+ from the sarcoplasm into the sarcoplasmic reticulum, leading to sustained vasoconstriction.
- C.
Excessive binding of Ca2+ to Troponin C in the VSMCs, preventing the detachment of myosin cross-bridges.
- D.
Overexpression of ANF receptors on the afferent arteriole, leading to a drastic reduction in Glomerular Filtration Rate (GFR).
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
ANF|Calcium_Dynamics|Myofilament_Protein_Composition
Why This Question Is Tricky
Common Mistakes
The Conceptual Pivot relies on integrating the endocrine function of ANF with the micro-anatomy of muscle contraction.
Students often memorize that 'ANF causes vasodilation' without understanding the intracellular Ca2+ dynamics required for it.
The primary trap (Option C) exploits a common structural misconception: failing to distinguish the myofilament protein composition across muscle types (Skeletal/Cardiac use Troponin, whereas Smooth Muscle uses Calmodulin).
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Excretory Products and Their Elimination - Class 11 |
| Concept | ANF Antagonism |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |