Now that we are done with the basics, let us move on to the segments and intervals. Since the ventricles contract stronger than the atria, the QRS complex which represents the contraction of the ventricles masks the atrial repolarization. You might ask, where is the atrial repolarization or the relaxation of the atria? Well, the answer to that is within the QRS complex. T wave represents ventricular repolarization where the two ventricles are relaxing. The QRS complex represents ventricular depolarization where the two ventricles are contracting. P wave represents atrial depolarization where the two atria are contracting. If the AV node and the Bundle of His fail, the left and right bundle branches and the Purkinje Fibers can conduct 20 – 40 bpm. However, if there is a blockage from the SA node, the AV node can conduct its electrical impulse and can generate 40 – 60 bpm same with the Bundle of His. If the SA node generates a normal impulse up to the Purkinje fibers, it conducts a heart rate of 60 – 100 beats per minute (bpm). These cells have the capabilities to fire electrical impulses in case there is a blockage in one or more components of the conduction system of the heart. So, if we make a pattern out of the conduction system of the heart, it goes like this: SA Node -> AV Node -> Bundle of His -> L and R Bundle Branches -> Purkinje Fibers These fibers simultaneously activate the left and right ventricles by directly stimulating the myocardium. That being said, if the SA node sends a weak impulse due to a block for example between the 2 nodes, the AV node can conduct its impulse.Ī lso known as atrioventricular bundle, are cardiac muscle fibers that conduct electrical impulses received from the AV node and bifurcate into two separate cells (one to the left and the other to the right) which is referred to as Left and Right Bundle Branches.Īs the left and right bundle branches extend towards the apex of the heart, they will then be termed as the Purkinje Fibers. The AV node is known as the “gate-keeper” of the heart as it decides what impulse to send through. As the conduction starts in the SA node, it goes directly to the AV node which is located within the border of the right atrium and the right ventricle.

6 second ekg strips practice