Impulse Generation in the Heart: A Simple Animation

The heart's electrical system begins with the sinoatrial node, also known as the SA node.This specialized structure is located in the upper wall of the right atrium.The SA node contains specialized cells that spontaneously generate electrical impulses, typically at a rate of sixty to one hundred beats per minute.These electrical impulses spread across both atria like ripples on water, causing them to contract simultaneously.This contraction pushes blood from the atria into the ventricles below, preparing for the next phase of the heartbeat.The SA node is called the heart's natural pacemaker because it sets the pace for the entire heart. If it were to malfunction, other tissues in the heart could take over, but at a slower rate.After the electrical impulse has spread across the atria, it reaches the atrioventricular node, which will carry the signal to the ventricles.After spreading through the atria, the electrical impulse reaches the atrioventricular node, or AV node.The AV node is strategically located at the boundary between the atria and ventricles.As the impulse reaches the AV node, it experiences a crucial delay of approximately 100 milliseconds.This delay is physiologically critical, as it allows the atria to fully contract and empty their blood into the ventricles before ventricular contraction begins.After this carefully timed delay, the impulse travels down the Bundle of His, a specialized conduction pathway.From there, the impulse enters the Purkinje fibers, an extensive branching network that spreads throughout the ventricular walls.This specialized conduction system ensures that the electrical impulse reaches all parts of the ventricles in a coordinated manner.The precise timing and organization of this conduction pathway allows the ventricles to contract in a synchronized wave-like motion, efficiently pumping blood to the lungs and body.