The singly nucleated cells of cardiac muscle are interconnected by intercalated discs. Cardiac muscle cells do have striations due to an internal ordering of actin and myosin. Like skeletal muscle, cardiac muscle possesses sarcoplasmic reticula and T-tubule systems.

Although isolated cardiac cells will contract spontaneously at period intervals, in the heart there are specialized pacemaker cells in the SA node that set the actual heart rate. These cells are influenced by the autonomic nervous system. Sympathetic stimulation increases the heart rate while parasympathetic stimulation decreases the heart rate.