Atrioventricular node the crista terminalis, and anteriorly, via the interatrial septum. Contraction of heart muscle cells requires depolarization and repolarization of their cell membranes. Movement of ions across cell membranes causes these events. The cardiac conduction system (and AV node part of it) coordinates myocyte mechanical activity. A wave of excitation spreads out from the sinoatrial node through the atria along specialized conduction channels. This activates the AV node. The atrioventricular node delays impulses by approximately 0.09s. This delay in the cardiac pulse is extremely important: It ensures that the atria have ejected their blood into the ventricles first before the ventricles
Node 4 Node 4 Node 4, also known as the Docking Hub System (DHS), is a proposed module of the International Space Station (ISS). As of 2011 NASA was considering a 40-month design and development effort for Node 4 that would result in its launch in late 2013. Node 4 would be built using the Node Structural Test Article (STA) and docked to the forward port of the Harmony module. The Structural Test Article was built to facilitate testing of ISS hardware and was intended to become Node 1. However, during construction, structural design flaws were discovered. The under-construction Node 2 was