Final answer:
In a junctional rhythm, the atria and ventricles beat independently due to an arrhythmia, often with the AV node taking over pacemaking. The normal heartbeat, or sinus rhythm, is coordinated by impulses from the SA node, traveling through the heart to the ventricles, which a pacemaker can help restore if disrupted.
Step-by-step explanation:
The rhythm where the atria and ventricles have independent pacemakers is typically referred to as an arrhythmia, and one specific type of arrhythmia is junctional rhythm, which originates from the atrioventricular (AV) node. Normally, the sinus rhythm is established by the heart's natural pacemaker located at the sinoatrial (SA) node. Electrical impulses generated at the SA node travel through the atria, causing them to contract, and then reach the AV node. After a brief pause, these impulses are conducted to the ventricles via the bundle of His and Purkinje fibers, resulting in ventricular contraction. Should an arrhythmia disrupt this process, an artificial pacemaker may be used to restore the normal rhythm.