Etymology: Johannes E. Purkinje
a complex fibrous network of large muscle cells that spread through the right and the left ventricles of the heart and carry the impulses that contract those chambers almost simultaneously. The fibers that connect with Purkinje's fibers start in the atrioventricular (AV) node in the right atrium of the heart, along the lower part of the interatrial septum. Impulses generated in the sinoatrial node travel through the muscle fibers of both atria of the heart, starting atrial contraction. As the impulse enters the AV node from the right atrium, it allows both atria to contract completely before the impulse spreads into the ventricles. The velocity of the impulse increases after the impulse leaves the AV node and spreads via the atrioventricular bundle (bundle of His) to the bundle branches, and finally to Purkinje's fibers. Purkinje's fibers are larger in diameter than ordinary cardiac muscle fibers and contain relatively few peripheral myofibrillae. They have abundant sarcoplasm and larger central nuclei than ordinary cardiac muscle. See also cardiac cycle, intraventricular block.