Sinonimi: cardiac pacemaker | sinoatrial node | SA node
Or sinoatrial node (SA node) In vertebrates, a group of muscle cells in the wall of the heart that contracts spontaneously and rhythmically, setting the pace for the contractions of the rest of the heart. The pacemaker's intrinsic rate of contraction is increased or decreased, according to the needs of the body, by stimulation from the autonomic nervous system. A specialized bit of heart tissue that controls the heartbeat; SYN. cardiac pacemaker, sinoatrial node, SA node.