Bachmann's bundle that area. The normal cardiac rhythm originates in the sinoatrial node, which is located in the right atrium near the superior vena cava. From there, the electrical activation spreads throughout the right atrium. There are at least four different locations where the activation can pass to the left atrium. Apart from Bachmann's bundle these are the anterior interatrial septum, posterior interatrial septum, and the coronary sinus. Because it originates close to the sinoatrial node and consists of long parallel fibers, Bachmann's bundle is, during sinus rhythm, the first of these connections to activate the left atrium. Bachmann's bundle In the
Sinoatrial node known as a spontaneous Ca spark. This increase in calcium within the cell then activates a sodium-calcium exchanger (NCX), which removes one Ca from the cell, and exchanges it for 3 Na into the cell (therefore removing a charge of +2 from the cell, but allowing a charge of +3 to enter the cell) therefore in-creasing the membrane potential. The calcium is later pumped back into the cell via calcium channels located on the cell membrane and SR membrane. The increase in membrane potential produced by these mechanisms, activates T-type calcium channels and then L-type calcium channels (which open very