Unlike skeletal muscle, cardiac muscle cannot undergo tetanic contraction. The physiological basis for this is:
- A The absence of sarcoplasmic reticulum
- B The low resting membrane potential
- C The long duration of the absolute refractory period ✓
- D The lack of actin-myosin cross-bridges
Correct answer: C. The long duration of the absolute refractory period
Explanation
The cardiac action potential has a prolonged plateau phase, resulting in an absolute refractory period that lasts almost as long as the mechanical contraction. This prevents summation of contractions and tetanus, allowing the heart to fill. Skeletal muscle has a much shorter refractory period, allowing tetanus.
Reference: Guyton and Hall Textbook of Medical Physiology, 14th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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