Question

The absolute refractory period begins with the onset of the _____ and terminates _____.

a) P wave, before the QRS complex
b) QRS complex, after the T wave
c) T wave, before the P wave
d) PR interval, after the ST segment

Answer 1

The absolute refractory period begins with the onset of the QRS complex and terminates after the T wave. This period reflects the time when cardiac cells cannot respond to a new electrical stimulus due to inactivated sodium channels.

Step-by-step explanation:

The question concerns the absolute refractory period and when it begins and ends in relation to an electrocardiogram (ECG) tracing. As per ECG physiology, the absolute refractory period begins with the onset of the QRS complex, which represents ventricular depolarization, and it terminates after the completion of the T wave, which signifies ventricular repolarization.

Therefore, the correct answer to the question would be option b) QRS complex, after the T wave. The absolute refractory period is the time during which the cardiac cells are unable to respond to a new electrical stimulus, primarily because the sodium channels are inactivated.