Muscle contraction RyRs are activated by a calcium trigger, which is brought about by the flow of through the L-type calcium channels. Furthermore, cardiac muscle tend to exhibit diad (or dyad) structures, rather than triads. Excitation-contraction coupling in cardiac muscle cells occurs when an action potential is initiated by pacemaker cells in the sinoatrial node or Atrioventricular node and conducted to all cells in the heart via gap junctions. The action potential travels along the surface membrane into T-tubules (the latter are not seen in all cardiac cell types) and the depolarisation causes extracellular to enter the cell via L-type calcium channels
Contraction band necrosis Contraction band necrosis Contraction band necrosis is a type of uncontrolled cell death (necrosis) unique to cardiac myocytes and thought to arise in reperfusion from hypercontraction, which results in sarcolemmal rupture. It is a characteristic histologic finding of a recent myocardial infarction (heart attack) that was partially reperfused. The name of the histopathologic finding comes from the appearance under the microscope; contraction bands are thick intensely eosinophilic staining bands (typically 4-5 micrometres wide) that span the short axis of the myocyte. They can be thought of extra thick striae, typical of cardiac muscle and striated muscle. Contraction band necrosis is