Final answer:
Cardiac contraction signals start at the sinoatrial (SA) node, move to the atrioventricular (AV) node, then travel through the bundle of His, the bundle branches, and Purkinje fibers. These signals coordinate the timely contraction of the atria and ventricles, essential for efficient blood pumping. An ECG can record this electrical activity.
Step-by-step explanation:
Cardiac contraction signals normally originate from the heart's internal pacemaker system. This pacemaking system starts at the sinoatrial (SA) node, which is located in the right atrium. From there, electrical signals spread through the atria causing them to contract in unison. Next, the signals reach the atrioventricular (AV) node, where they are delayed before continuing to the ventricles. The impulse moves through the bundle of His, the left and right bundle branches, and finally the Purkinje fibers, triggering the ventricles to contract. This orchestrated series of electrical events ensures that the atria have emptied into the ventricles before ventricular contraction occurs, efficiently pumping blood out of the heart.
An electrocardiogram (ECG) is a tool that can measure these electrical currents across the skin and provide a visual representation of cardiac electrical activity.