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Question #47393
The Question
Following an accidental parathyroidectomy, a patient develops severe asphyxiation despite having unobstructed airways and healthy alveolar tissue. Which of the following accurately describes the physiological basis of this respiratory failure?
Options
- A.
Hypocalcemia increases neuronal membrane excitability, causing tetanic spasms of the diaphragm and external intercostals, thereby preventing rhythmic thoracic ventilation.
- B.
Decreased blood calcium levels deplete the sarcoplasmic reticulum, preventing calcium binding to troponin and causing flaccid paralysis of the rib cage.
- C.
The absence of Parathyroid Hormone (PTH) leads to hypercalcemia, which directly depresses the respiratory rhythm centre in the medulla oblongata.
- D.
Low extracellular calcium inhibits the release of acetylcholine at the neuromuscular junctions of the intercostal muscles, halting inspiration.
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
Intercostal_Muscles|Diaphragm|Parathyroid_Hormone|Calcium_Ion_Channels
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Students frequently confuse the role of intracellular calcium (from the sarcoplasmic reticulum, required for muscle contraction) with extracellular calcium (in blood/ECF, required for stabilizing neuronal membranes).
A common misconception is that low blood calcium causes muscle weakness (flaccid paralysis) because calcium is needed for cross-bridge formation.
However, the critical NCERT concept is that low ECF calcium causes neuronal hyperexcitability, leading to 'Tetany' (spasms).
Applying this to the respiratory system reveals that these spasms lock the thoracic cavity, preventing the volume changes necessary for pulmonary ventilation.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Locomotion and Movement - Class 11 |
| Concept | Rib Cage Architecture |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |