What are the three electrical events that occur at the sarcolemma of cardiac muscle cells?

What are the three electrical events that occur at the sarcolemma of cardiac muscle cells?

• A. Atrial depolarization (P wave), 2. Ventricular depolarization (QRS complex), 3. Ventricular repolarization (T wave)
• B. Atrial repolarization, 2. Ventricular depolarization, 3. Atrial depolarization
• C. P wave, 2. QRS, 3. U wave
• D. Atrial depolarization, 2. Ventricular repolarization, 3. Atrial repolarization

Answer: (A)

The sequence reflects the main electrical events across the sarcolemma of cardiac muscle as the heart activates and then relaxes. First, atrial depolarization occurs, which shows up on the ECG as the P wave. Next comes ventricular depolarization, represented by the QRS complex as the ventricles activate. Finally, ventricular repolarization appears as the T wave, signaling the ventricles returning to their resting state. Atrial repolarization does happen, but it is masked by the large QRS complex and not seen as a separate deflection on the standard ECG. The U wave isn’t part of the normal triad of events. So the best description is atrial depolarization, ventricular depolarization, and ventricular repolarization.

The sequence reflects the main electrical events across the sarcolemma of cardiac muscle as the heart activates and then relaxes. First, atrial depolarization occurs, which shows up on the ECG as the P wave. Next comes ventricular depolarization, represented by the QRS complex as the ventricles activate. Finally, ventricular repolarization appears as the T wave, signaling the ventricles returning to their resting state. Atrial repolarization does happen, but it is masked by the large QRS complex and not seen as a separate deflection on the standard ECG. The U wave isn’t part of the normal triad of events. So the best description is atrial depolarization, ventricular depolarization, and ventricular repolarization.