What does the P wave on an ECG represent?

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Prepare for the PLTW Biomedical Science Test. Study with flashcards and multiple choice questions, each question comes with hints and explanations. Get ready for your exam!

Multiple Choice

What does the P wave on an ECG represent?

Explanation:
The P wave shows atrial depolarization—the electrical activity that makes the atria contract. When the SA node fires, the impulse spreads across the atria, causing them to depolarize and push blood into the ventricles. This electrical event appears as the P wave, which occurs before the ventricles’ electrical activity. The big spike afterward—the QRS complex—represents ventricular depolarization and contraction, while the T wave reflects ventricular repolarization (relaxation). Atrial repolarization does occur, but it’s masked by the QRS complex and not seen as a separate wave.

The P wave shows atrial depolarization—the electrical activity that makes the atria contract. When the SA node fires, the impulse spreads across the atria, causing them to depolarize and push blood into the ventricles. This electrical event appears as the P wave, which occurs before the ventricles’ electrical activity. The big spike afterward—the QRS complex—represents ventricular depolarization and contraction, while the T wave reflects ventricular repolarization (relaxation). Atrial repolarization does occur, but it’s masked by the QRS complex and not seen as a separate wave.

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