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Question #46343
The Question
A patient presents with severe respiratory distress. Investigations reveal a localized toxin that completely blocks the release of calcium ions from the sarcoplasmic reticulum of the diaphragm muscle fibers during neural stimulation. Which of the following accurately describes the immediate state of the sarcomere and the resulting effect on pulmonary mechanics?
Options
- A.
Calcium fails to bind to the regulatory protein tropomyosin, leaving myosin-binding sites masked and drastically reducing the functional residual capacity.
- B.
The unmasking of active sites on F-actin is prevented, leading to a failure of diaphragm contraction and an inability to increase thoracic volume in the antero-posterior axis.
- C.
Cross-bridge formation is halted because ATP cannot be hydrolyzed by the myosin head, leading to a restrictive respiratory pattern with an increased tidal volume.
- D.
The diaphragm undergoes sustained tetanic contraction due to the lack of calcium-dependent relaxation, locking the thoracic chamber in a state of forced expiration.
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
Diaphragm|Cross-bridge_Cycling_Energy|Calcium_Dynamics|Sarcomere_Functional_Boundaries
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot & Cross-Chapter Synthesis: This question forces students to integrate 'Locomotion and Movement' (Sliding Filament Theory) with 'Breathing and Exchange of Gases' (Mechanism of Breathing).
The primary trap is functional/anatomical specificity: students frequently confuse Troponin with Tropomyosin as the calcium-binding site, and often forget that the diaphragm specifically increases thoracic volume in the antero-posterior axis (while external intercostals increase it in the dorso-ventral axis).
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Breathing and Exchange of Gases - Class 11 |
| Concept | Diaphragm Mechanics |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |