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New SAN is from the upper part of the best atrium laterally toward entrances of the superior vena cava. Books show an element pacemaker step potential, https://datingmentor.org/local-hookup/rockford/ nevertheless SAN is largely a little a beneficial heterogeneous design, each other morphologically and you will electrophysiologically [ 5 ]. The main pacemaker also can change area having alterations in autonomic build [ six ]. With this particular caveat planned it is helpful to look at the head currents root excitability.
At the molecular level SAN cells express both Cav1.2 and Cav1.3. Cav1.2 is the classic L-type channel present throughout the heart that is responsible for calcium entry promoting calcium-induced calcium release from the sarcoplasmic reticulum and in the SA node is responsible for some of the action potential depolarization [ 7 ]. v1.3 activates at more hyperpolarised potentials and contributes to pacemaking [ 8 , 9 ]. Sodium currents are less obvious as the main driver of depolarization. However, tetrodotoxin-resistant and sensitive currents have been described and these may be present in the more peripheral parts of the node adjacent to the atrial tissue [ 5 ]. Sodium channel mutations in SCN5A result in cardiac conduction disease [ 10 ].