<P> Under normal conditions , electrical activity is spontaneously generated by the SA node , the cardiac pacemaker . This electrical impulse is propagated throughout the right atrium , and through Bachmann 's bundle to the left atrium , stimulating the myocardium of the atria to contract . The conduction of the electrical impulses throughout the atria is seen on the ECG as the P wave . </P>
when does the sa node begin electrical signaling
spontaneously