sinoatrial nodesinoatrial node
pacemaker (sense )
sometimes called si·no·auric′u·lar node
Origin of sinoatrial node; from sinus + atrial
A small mass of specialized cardiac muscle fibers located in the posterior wall of the right atrium of the heart that acts as a pacemaker by generating at regular intervals the electric impulses of the heartbeat. Also called sinoauricular node, sinus node.