Purkinje fibers initiate spontaneous action potentials, which cause the ventricles to contract early. Action potentials are not delayed sufficiently at the AV node. Spontaneous action potentials in the SA node overlap such that the repolarizing phase of one action potential cancels out the depolarizing phase of the next. Action potentials propagate into the ventricles before the contractile cells have repolarized from the previous heartbeat. Submit

The Purkinje fibers are fascinating components of the heart's conduction system. They allow for a rapid and coordinated contraction of the ventricles, ensuring that the heart pumps blood efficiently. This unique fiber network plays a pivotal role in the heart's electrical system, helping to prevent chaotic rhythms that can occur if the timing of contractions is disrupted. In practice, understanding the timing of action potentials is crucial for diagnosing and treating cardiac arrhythmias. Medications can be designed to target specific phases of these action potentials, and interventions like catheter ablation can help correct conduction pathways that may lead to dangerous scenarios like fibrillation, ensuring the heart works as a well-tuned machine!