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nmdcat.online July 28, 2026

The functional significance of the absolute refractory period in cardiac muscle is primarily to:

A. Allow the sarcoplasmic reticulum to refill with calcium
B. Prevent tetanic contractions that would stop the heart from pumping
✓
C. Ensure that the ventricles contract before the atria
D. Give the intercalated discs time to transmit the action potential

📝 Explanation

Cardiac muscle has an unusually long action potential and absolute refractory period (lasting almost as long as the contraction itself). This biological adaptation prevents multiple action potentials from summing and causing tetanus (sustained contraction), which would be fatal as the heart must relax to fill with blood.

📖 Additional Information

  • Allow the sarcoplasmic reticulum to refill with calcium
  • Prevent tetanic contractions that would stop the heart from pumping
  • Ensure that the ventricles contract before the atria
  • Give the intercalated discs time to transmit the action potential

Cardiac muscle has an unusually long action potential and absolute refractory period (lasting almost as long as the contraction itself). This biological adaptation prevents multiple action potentials from summing and causing tetanus (sustained contraction), which would be fatal as the heart must relax to fill with blood.

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