ï»¿ Microscopic Appearance of Cardiac Muscle Cardiac muscle makes up the wall of the heart. Cardiac muscle is involuntary muscle, meaning that it's regulated by the autonomic nervous system. Let's examine the microscopic appearance of cardiac muscle. At a low magnification, it's hard to see the characteristics that are unique to cardiac muscle. At a higher magnification, cardiac muscle resembles colorful bamboo. Individual cardiac muscle cells have a cylindrical branching shape. Each of these branches connects to other cardiac muscle cells. So, cardiac muscle cells are interconnected. The junction between one cardiac muscle cell and the neighboring cell is an intercalated disc. The intercalated discs are visible at higher magnifications. Intercalated discs contain gap junctions which aren't visible using light microscopy. Gap junctions are tiny pores that connect the cytoplasm of neighboring cells. Neighboring cells communicate through the gap junctions contained in the intercalated discs. Cardiac muscle is striated. These striations may be light in color and aren't as prominent as the striations seen in skeletal muscle. Notice that the striations run perpendicular to the longitudinal axis of the cell. And run in the same plane as the intercalated discs. But the intercalated discs typically stain darker. Let's finish by reviewing the microscopic appearance of cardiac muscle. Cardiac muscle at low magnification. Cardiac muscle at high magnification. Cardiac muscle cell. Intercalated discs.