Which wave is produced when a signal from the SA node spreads through the atria?

The P wave is generated when the electrical impulse from the sinoatrial (SA) node propagates through the atria. This wave reflects the depolarization of the atrial myocardium, which occurs as the electrical signal stimulates the atrial muscle to contract. During this phase, the atria squeeze to push blood into the ventricles. The P wave corresponds to the initial electrical activity seen on an electrocardiogram (ECG), indicating that the heart is preparing for the next phase of the cardiac cycle. Understanding the role of the P wave is critical for interpreting cardiac rhythms and diagnosing various cardiac conditions.