he process of cardiac excitation begins with the sinoatrial (SA) node, which generates an action potential (excitation signal). This signal propagates across the atria, triggering their contraction. Upon reaching the atrioventricular (AV) node, the signal experiences a brief delay, allowing the atria to contract before the ventricles are stimulated fully. From the AV node, the excitation is transmitted to His bundle, which runs along the interventricular septum. The bundle of His branches into Purkinje fibres, which distribute the signal throughout the ventricles, causing them to contract and effectively pump blood.

Alpha, Beta and Gamma

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