How does the AV node affect impulses during atrial flutter?

The correct response highlights the role of the AV node in modulating the electrical impulses during atrial flutter. In this condition, the atria experience rapid reentrant circuits that can generate waves of electrical activity at a very high frequency. However, the AV node acts as a critical control point that does not allow all of these impulses to pass through to the ventricles.

Specifically, the AV node selectively conducts impulses, meaning it will only allow a certain number of atrial impulses to be transmitted to the ventricles and will block others. This selective blockage prevents the ventricles from responding to every atrial impulse, which could lead to dangerously fast heart rates and compromise cardiac output. The typical response of the AV node during atrial flutter is to conduct a limited number of impulses, often resulting in a ventricular response that is slower than the atrial rate.

This understanding is pivotal in recognizing how the AV node protects the heart from being overwhelmed during such arrhythmias, ensuring that while the atria flutter rapidly, the ventricles maintain a more controlled rhythm, thus supporting effective circulation.