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Question #45723
The Question
A patient presents with severe skeletal muscle weakness and fatigue. Clinical evaluation reveals a hypersecreting tumor of the adrenal cortex, leading to chronic overactivation of the RAAS pathway. Based on the principles of neural and muscular physiology, which of the following best explains the molecular basis of this neuromuscular impairment?
Options
- A.
Excessive Na+ reabsorption depolarizes the sarcolemma, causing continuous Ca2+ efflux from the sarcoplasmic reticulum and rapid ATP depletion.
- B.
Enhanced K+ excretion leads to hypokalemia, which hyperpolarizes the sarcolemma, thereby increasing the threshold required to trigger Ca2+ release for troponin binding.
- C.
Aldosterone directly binds to intracellular receptors in muscle fibers, inhibiting the ATPase activity of the heavy meromyosin (HMM) head.
- D.
Decreased K+ levels in the blood prevent the repolarization of the motor end plate, leading to sustained muscle contraction and subsequent fatigue.
Check Your Answer
Correct Answer
Step-by-Step Solution
Explanation
How the Examiner Thinks
Comparative_Analysis
Sharpen your ability to evaluate multiple scenarios and distinguish between competing potential answers.
Concepts Behind This Question
Aldosterone|Troponin|Sarcoplasmic_Reticulum|Potassium_Excretion
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Students often memorize 'Aldosterone = Na+ retention = High BP' but neglect the 'K+ excretion' aspect.
Furthermore, a common misconception is how K+ imbalances affect membrane potential.
Students often assume low extracellular K+ would depolarize the cell, but it actually increases the efflux gradient, causing hyperpolarization and flaccid paralysis (weakness), rather than tetany or sustained contraction.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Excretory Products and Their Elimination - Class 11 |
| Concept | RAAS Pathway Feedback Loop |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |