If a stimulus reaches the excitable gap during a reentrant loop, what is the consequence?

If a stimulus reaches the excitable gap during a reentrant loop, what is the consequence?

• A. It shortens the cycle length
• B. It delays the next impulse
• C. It breaks the rhythm
• D. It has no effect

Answer: (C)

The idea being tested is the excitable gap in a reentrant circuit. Inside a reentry loop there is a segment of tissue that has recovered from refractoriness and is ready to be excited—the excitable gap. When a stimulus arrives at this gap, it can propagate into the circuit and interact with the circulating wavefront in such a way that the reentrant loop is interrupted. That disruption stops the ongoing reentrant impulse, breaking the tachycardia and allowing rhythm to normalize. If the stimulus hit tissue that was still refractory, it wouldn’t propagate; arriving outside the gap wouldn’t terminate the loop. So, reaching the excitable gap commonly terminates the reentrant rhythm.

The idea being tested is the excitable gap in a reentrant circuit. Inside a reentry loop there is a segment of tissue that has recovered from refractoriness and is ready to be excited—the excitable gap. When a stimulus arrives at this gap, it can propagate into the circuit and interact with the circulating wavefront in such a way that the reentrant loop is interrupted. That disruption stops the ongoing reentrant impulse, breaking the tachycardia and allowing rhythm to normalize. If the stimulus hit tissue that was still refractory, it wouldn’t propagate; arriving outside the gap wouldn’t terminate the loop. So, reaching the excitable gap commonly terminates the reentrant rhythm.