From my reading, the action potential is generated by pacemaker cells within the SA node and the conduction system of the heart carries the action potential to the cardiac muscle cells. I was just wondering whether the action potential travels through gap junctions or along the sarcolemma? It would need to travel along the sarcolemma to activate L-type calcium channels during muscle contraction, but how does the action potential actually travel from the SA node to the membrane of the cell? How does it just 'jump' to the surface of the muscle cell?

In addition to that inquiry, when do action potentials travel through the gap junction then? Does the action potential travel through both the sarcolemma and the gap junctions?



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