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Question #46379
The Question
Cardiac muscle is highly resistant to fatigue under normal physiological conditions, functioning as an obligate aerobic tissue. However, during acute coronary ischemia, the myocardium rapidly loses contractility, whereas skeletal muscles can sustain temporary activity under oxygen debt. Which of the following structural or metabolic features best explains this inability of cardiac muscle to tolerate hypoxia?
Options
- A.
Cardiac myocytes possess a highly developed sarcoplasmic reticulum that rapidly depletes intracellular calcium during hypoxia.
- B.
The myocardium has a negligible reserve of glycolytic enzymes and relies almost entirely on oxidative phosphorylation.
- C.
High myoglobin content in cardiac myocytes competitively inhibits the enzyme lactate dehydrogenase during anaerobic conditions.
- D.
Cardiac muscle fibers lack intercalated discs in their ischemic zones, preventing the propagation of anaerobic action potentials.
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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
Myoglobin|Mitochondrial density|Lactate accumulation
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Distinguishing the metabolic profiles of red, white, and cardiac muscle fibers.
Students often know cardiac muscle does not fatigue, but fail to link this to its obligate aerobic nature and lack of glycolytic capacity.
The trap lies in assuming cardiac muscle has the same anaerobic backup as skeletal muscle but simply 'chooses' not to use it, whereas it actually lacks the enzymatic machinery to sustain contraction anaerobically.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Body Fluids and Circulation - Class 11 |
| Concept | Coronary Circulation Specifics |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |