What does depolarization of the heart mean?

Depolarization of the heart refers to the process by which the cells in the heart muscle, known as cardiomyocytes, undergo a change in electrical charge. This change is crucial for the proper functioning of the heart, as it triggers the contraction of the heart muscle, which in turn pumps blood throughout the body. In a healthy heart, depolarization begins in a specific region called the sinoatrial (SA) node, which is the natural pacemaker of the heart. The SA node is located in the right atrium and is responsible for generating electrical impulses that spread throughout the heart muscle. When these impulses reach the atrial cells, they cause the cells to depolarize, leading to the contraction of the atria. This is the first phase of the heart's contraction cycle and is represented by the P wave on an electrocardiogram (ECG). Following atrial depolarization, the electrical impulses travel to the atrioventricular (AV) node, which is located at the lower part of the right atrium and serves as a relay station. From the AV node, the impulses move through a specialized conduction system and reach the ventricles. The ventricles are the two lower chambers of the heart that pump blood to the lungs and the rest of the body. When the ventricles depolarize, they contract forcefully, pushing blood out of the heart. This ventricular depolarization is represented by the QRS complex on the ECG. In summary, depolarization is a vital step in the cardiac cycle that ensures the heart's coordinated contraction and efficient blood circulation.

Depolarization occurs in the four chambers of the heart: both atria first, and then both ventricles. The sinoatrial (SA) node on the wall of the right atrium initiates depolarization in the right and left atria, causing contraction, which is symbolized by the P wave on an electrocardiogram.