Although cardiac muscle is striated like skeletal muscle, the striations are not so readily apparent.  Cardiac muscle cells are short, branched and interconnected.  Each cell usually contains one centrally located nucleus.  Cardiac muscle cells are joined end-to-end at specialized junctional zones called intercalated discs [pointed to by the blue arrows].  These discs allow force to be transmitted from one cell to another.  Additionally, they contain gap junctions that allow an action potential in one cell to pass directly to an adjoining cell through these electrical synapses.