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Cardiac muscle cells are relatively short and branched, connecting with each other via intercalated discs which interlock cell membranes of adjacent cardiac muscle fibers via desmosomes and gap junctions, therefore all cardiac muscle can contract together (or in a single coordinated fluid movement). Cardiac muscle cells usually have only one or two nuclei, but contain numerous amounts of mitochondria which provide a constant supply of cellular energy that gives cardiac muscle a high resistance to fatigue. The increased number of mitochondria require a high oxygen consumption by cardiac muscle cells, and unlike skeletal muscle which can undergo anaerobic respiration, cardiac muscles rely exclusively on oxygen for energy metabolism.

To maintain an ongoing and steady cycle of heart contraction, some specialized cardiac muscle fibers create a 'conduction system' throughout the myocardium of the heart. These specialized cardiac muscles are non-contractile cells which are capable of initiating and distributing electrical impulses (action potentials) throughout the myocardium. This conduction system is composed of six key parts, including two collections of auto-rhythmic (self-excitable) cells which have unstable resting cell membranes (RMPs) that continuously and rhythmically depolarize. This intrinsic conduction system allows depolarization and contraction of cardiac muscle independent of the nervous system. Thus even without nervous innervation, the heart continues to beat rhythmically on its own.