Osmosis video - Cardiac conduction system

The heart is a muscular organ that contracts and relaxes to pump blood throughout the body. Electrical signals originate in the sinoatrial (SA) node in the right atrium. The depolarization wave from the SA node travels to the atrioventricular (AV) node and the left atria. From the AV node, the depolarization wave travels through the bundle of His and the Purkinje fibres, from where it spreads to the rest of the heart's muscle. This impulse triggers the heart muscles to contract and pump blood.