- A Blood from flowing backward through the semilunar and AV valves
- B Tetanic (continuous) contraction of the heart (ensures rhythmic pumping)
- C Autonomic nerve signals from the vagus and sympathetic trunk from reaching the SA node
- D Excessively rapid filling of the ventricles during diastole
Correct answer: B. Tetanic (continuous) contraction of the heart (ensures rhythmic pumping)
Explanation: The refractory period of cardiac muscle cells prevents tetanus. The heart must relax between beats to fill with blood for the next contraction.
Concept context
Blood, lymph, the heart, the cardiac cycle, blood pressure, and ECG. High NEET weightage.