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Question:
What is the electrical output that the SA Node and/or AV Node put out when emitting an electrical charge? Is it sustainable or measurable and is it only during the QRS Complex?



Replies:
The EKG measures and amplifies the electrical conductivity of the heart. It is a recording of the electrical changes that accompany each cardiac cycle and is a composite of ALL of the action potentials produced by ALL heart muscle fibers during each heartbeat. The first wave on an EKG cycle is the P wave and represents atrial depolarization which spreads from the SA node over the atria. About 0.1 sec after the P wave begins the atria contract. The second wave is the QRS complex which represents the onset of ventricular depolarization. It is delayed at the AV node to allow time for the ventricles to fill with blood. Shortly after the QRS complex begins, ventricular contraction occurs. The third wave or T wave signals ventricular REpolarization. Atrial depolarization doesn't show up because it is buried in the QRS wave. I couldn't find information on the exact voltage coming from the heart.

Van Hoeck



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