cardiac muscle - the muscle tissue of the heart; adapted to continued rhythmic contractionticker, heart, pump - the hollow muscular organ located behind the sternum and between the lungs; its rhythmic contractions pump blood through the body; "he stood still, his heart thumping wildly" papillary muscle - any of several muscles associated with the atrioventricular valves; "the papillary muscles contract during systole to prevent regurgitation of blood into the atria" atrioventricular node - a node of specialized heart muscle located in the septal wall of the right atrium; receives impulses from the sinoatrial node and transmits them to atrioventricular bundle myocardium - the middle muscular layer of the heart wall Purkinje fiber - a specialized cardiac muscle fiber that is part of the Purkinje network |