Final answer:
The AV node typically has an intrinsic firing rate of 40-60 beats per minute, not the stated 20 to 40 beats per minute, making the statement False.
Step-by-step explanation:
The statement that the intrinsic rate of the AV junction is 20 to 40 beats/min is False. The AV node, or atrioventricular node, is an important part of the heart's electrical conduction system. It serves as a gateway that slows the electrical current before it enters the ventricles.
This delay is crucial because it ensures that the atria have time to contract and pump blood into the ventricles before they begin to contract. The normal intrinsic firing rate of the AV node is actually 40-60 beats per minute. If the SA node were to fail, the AV node would take over as the heart's pacemaker; however, it would only be able to generate a heart rate of 40-60 beats per minute, not the stated 20-40 beats per minute.
Various factors in the heart could induce different rates of impulses, as the AV node can transmit impulses maximally at 220 beats per minute under extreme stimulation. Yet, the typical inherent firing rate without the influence of the SA node is still 40-60 beats per minute.
In absence of AV node activity, the next level in the conduction pathway, the atrioventricular bundle or Bundle of His, would fire at an inherent rate of approximately 30-40 impulses per minute. Lower down the pathway, the bundle branches and Purkinje fibers have even slower inherent rates.