Heart is established by the sinoatrial node, the heart's pacemaker. Here an electrical signal is created that travels through the heart, causing the heart muscle to contract. The sinoatrial node is found in the upper part of the right atrium near to the junction with the superior vena cava. The electrical signal generated by the sinoatrial node travels through the right atrium in a radial way that is not completely understood. It travels to the left atrium via Bachmann's bundle, such that the muscles of the left and right atria contract together. The signal then travels to the atrioventricular node. This
Sinoatrial node the 3 phases of a sinoatrial node action potential. In the ventricular action potential, there are 5 phases (labelled 0-4), however pacemaker action potentials don’t have an obvious phase 1 or 2. Phase 4 This phase is also known as the pacemaker potential. Immediately following an action potential, when the membrane potential is very negative (it is hyperpolarised) the voltage slowly begins to increase. This is initially due to the closing of potassium channels, which reduces the flow of potassium ions (I) out of the cell (see phase 3, below). Alongside the deactivation of the potassium channels, channels known as