<P> The contraction of cardiac muscle ( heart muscle ) in all animals is initiated by electrical impulses known as action potentials . The rate at which these impulses fire controls the rate of cardiac contraction , that is , the heart rate . The cells that create these rhythmic impulses , setting the pace for blood pumping , are called pacemaker cells , and they directly control the heart rate . They make up the cardiac pacemaker , that is , the natural pacemaker of the heart . In most humans , the concentration of pacemaker cells in the sinoatrial ( SA ) node is the natural pacemaker , and the resultant rhythm is a sinus rhythm . </P>
<P> The contraction of cardiac muscle ( heart muscle ) in all animals is initiated by electrical impulses known as action potentials . The rate at which these impulses fire controls the rate of cardiac contraction , that is , the heart rate . The cells that create these rhythmic impulses , setting the pace for blood pumping , are called pacemaker cells , and they directly control the heart rate . They make up the cardiac pacemaker , that is , the natural pacemaker of the heart . In most humans , the concentration of pacemaker cells in the sinoatrial ( SA ) node is the natural pacemaker , and the resultant rhythm is a sinus rhythm . </P>
what node serves as the pacemaker of the heart
what node serves as the pacemaker of the heart
the sinoatrial ( SA ) node
the sinoatrial ( SA ) node