Final answer:
Junctional rhythms are initiated in the area of the AV junction and the AV node can become a secondary pacemaker in the event of a conduction block, typically initiating contractions at a rate of 40-60 beats per minute as shown by an ECG.
Step-by-step explanation:
The rhythms that are initiated in the area of the atrioventricular (AV) junction are known as junctional rhythms. In the event of a conduction block at the sinoatrial (SA) node, the AV node can serve as a secondary pacemaker for the heart, initiating contractions at a rate of 40-60 beats per minute, which is typically adequate to maintain consciousness. In more severe cases, such as a third-degree AV block, there is no correlation between the P waves (atrial activity) and the QRS complexes (ventricular activity), indicating a complete disconnect in the atrial-to-ventricular impulse conduction. This situation is revealed through an electrocardiogram (ECG), which would show an independent atrial rhythm while the AV node maintains a slower but steady ventricular rhythm.