How does the AV node respond during atrial flutter?

• A. Blocks all impulses from reaching the ventricles
• B. Allows all impulses to pass through
• C. Blocks some impulses from reaching the ventricles
• D. Creates new impulses independently

Answer: (C)

The correct response regarding how the atrioventricular (AV) node behaves during atrial flutter is that it blocks some impulses from reaching the ventricles. In atrial flutter, the atria contract at a very high rate due to a reentrant circuit, resulting in numerous impulses being sent to the AV node. However, the AV node cannot transmit all of these rapid impulses to the ventricles because it has inherent conduction limitations designed to protect the ventricles from being stimulated at excessively high rates.

During this condition, the AV node selectively conducts some of the impulses while blocking others, typically allowing a ratio of impulses through, like 2:1 or 3:1, depending on how fast the atria are contracting. This selective conduction helps maintain a more stable heart rate and prevents the ventricles from beating too rapidly, which could lead to compromised cardiac output.