Which wave is primarily involved in the atrial contraction phase?

Which wave is primarily involved in the atrial contraction phase?

• A. P wave
• B. QRS complex
• C. T wave
• D. U wave

Answer: (A)

The P wave is primarily involved in the atrial contraction phase. It represents the depolarization of the atria, which is the electrical activity that triggers the contraction of the atrial muscle. As the atria depolarize, they contract and push blood into the ventricles, contributing to the heart's overall pumping action. This phase is crucial for ensuring that the ventricles receive an adequate volume of blood before they themselves contract.

In contrast, the QRS complex represents the depolarization of the ventricles and occurs after the P wave; hence, it is associated with ventricular contraction rather than atrial contraction. The T wave indicates the repolarization of the ventricles, allowing them to recover from contraction, and the U wave is often considered a normal variant and is not directly involved in any contraction phase. Understanding these distinctions is essential for interpreting EKGs and recognizing the phases of the cardiac cycle as they relate to the electrical activity of the heart.