The
sinoatrial node (often abbreviated
SA node; also commonly called the
sinus node and less commonly the
sinuatrial node) is the normal
natural pacemaker of the
heart and is responsible for the initiation of the
heartbeat. It spontaneously generates an electrical impulse, which after
conducting throughout the heart, causes the heart to contract. Although the electrical impulses are generated spontaneously, the rate of the impulses (and therefore the heart rate) is set by the nerves innervating the sinoatrial node. The sinoatrial node is located in the myocardial wall near where the
sinus venosus joins the right
atrium (upper chamber); hence + .