How is cardiac muscle cell structure relate to its function?
Heart cells have both similarities and differences to skeletal muscle cells. Heart muscle cells are striated. The striations are due to the same myofibrils (composed of actin and myosin) that are present in skeletal muscle cells. The sliding cross-bridge contraction mechanism of these myofibrils is also the same as in skeletal muscle. Heart muscle cells, however, are much smaller than skeletal muscle cells and have only one nucleus. The small cells are “fused” to each other at the dark areas called intercalated disks . Electrical resistance across these disks is very low, thanks to the relatively free diffusion of ions through their gap junctions which contain many channels through which ions can travel from on cell to the next. As a result, if one cell fires an action potential, the signal will quickly spread to the whole tissue of connected cells. Therefore, the heart muscle cells function all together as a syncytium. The heart is actually composed of two syncytia of cells: the atria
