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HEALTH • MEDICINE • WELLNESS • HEALTH • MEDICINE • WELLNESS • HEALTH • MEDICINE • WELLNESS • HEALTH • MEDICINE • WELLNESS • HEALTH • MEDICINE • WELLNESS • HEALTH • MEDICINE • WELLNESS • HEALTH • MEDICINE • WELLNESS • HEALTH • MEDICINE • WELLNESS • HEALTH • MEDICINE • WELLNESS

AIKEN-AUGUSTA’S MOST SALUBRIOUS NEWSPAPER • FOUNDED IN 2006

FEBRUARY 3, 2017

It’s got the beat Sure, we all know that already. But why? How? Every year February is observed as American Heart Month, so at every turn for the next several weeks we’ll be reading stories about heart health and heart disease statistics and prevention and all other things heart-related. All month long our hearts will be beating, tallying an average of 100,000 beats a day for each and every one of us. In fact, even when a heart is cut out of the chest for a heart transplant operation (or an Aztec sacrifice, for that matter) it will continue to beat sitting in a pan awaiting placement in its new home. Why? How? What makes the heart go lub-dub, lub-dub, lub-dub all day every day — and all night every night? It’s a hearty topic for our intermittent series called Body Parts. Keeping the beat Like just about everything else in the human body (and the natural world as a whole), the heart is extremely complex and sophisticated, and its mechanism of pumping is involved and elaborate. A simple lub-dub it is not. As suggested by the illustration, the heart has an electrical system. After all, it’s getting an EKG, the E of which stands for “electro.” (EKG stands for electrocardiogram.) That’s where the beat comes from, the regular pulse, the constant rhythm of our hearts: it’s a reaction to a mild electric shock that originates within the heart itself. The mini-jolt is generated in the sinoatrial (SA) node located in the right atrium of the heart. The jolt is triggered when the right and left atria, the top chambers of the heart, fill with blood. “Full” activates the SA node, which zaps both atria, causing them to contract or squeeze their contents through one-way valves (the tricuspid valve on the heart’s right side, the mitral valve on the left) down into the right and left ventricles. While the ventricles are filling with blood, the SA node’s electrical signal reaches a relay switch of sorts known as the atrioventricular (AV) node. The AV

BODY PARTS: THE SERIES

Please see THE BEAT page 2

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