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The Human Heart Runs on Electricity
The heart’s cardiac conduction system — specialized cells that work like an electrical generator — tells the heart when and how fast to beat. First, pacemaker cells in the sinoatrial (SA) node send out an electrical signal that cascades down the left and right atria, causing the chambers to contract. That squeezes blood through the mitral and tricuspid valves into the left and right ventricles. Another group of pacemaker cells in the atrioventricular (AV) node sends out another signal telling the ventricles to start contracting, which pushes the blood through two more valves and out to the body. Then the SA node shoots out a fresh signal, and the process repeats.
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