Intercalated discs contain gap junctions and desmosomes. The gap junctions, which are protein-lined tunnels, allow direct transmission of the depolarizing current from cell to cell, across the chambers of the heart, so that the cells contract in unison.
Cardiac muscle cells are equipped with three distinct types of intercellular junction--gap junctions, "spot" desmosomes, and "sheet" desmosomes (or fasciae adherentes)--located in a specialized portion of the plasma membrane, the intercalated disk.
Intercalated discs are unique structural formations found between the myocardial cells of the heart. They play vital roles in bonding cardiac muscle cells together and in transmitting signals between cells.
