Which statement best characterizes the excitable gap in a reentrant circuit?

Which statement best characterizes the excitable gap in a reentrant circuit?

• A. The refractory tissue
• B. The boundary tissue
• C. The region that is ready to be excited and can interrupt the circuit
• D. The permanent tissue

Answer: (C)

The excitable gap is the portion of tissue inside a reentrant circuit that has recovered from refractoriness and is ready to be excited again. As the circulating impulse moves around the loop, tissue behind remains refractory while tissue ahead has regained excitability. This ready-to-fire region is the excitable gap, and it can be captured by the advancing wavefront or, if a premature impulse arrives, it can interrupt the circuit. If the gap is too small or absent, the wavefront hits still-refractory tissue and reentry terminates; if it’s present, reentry can persist. Refractory, boundary, or permanent tissue does not fit this concept because they cannot be excited to continue or interrupt the loop.

The excitable gap is the portion of tissue inside a reentrant circuit that has recovered from refractoriness and is ready to be excited again. As the circulating impulse moves around the loop, tissue behind remains refractory while tissue ahead has regained excitability. This ready-to-fire region is the excitable gap, and it can be captured by the advancing wavefront or, if a premature impulse arrives, it can interrupt the circuit. If the gap is too small or absent, the wavefront hits still-refractory tissue and reentry terminates; if it’s present, reentry can persist. Refractory, boundary, or permanent tissue does not fit this concept because they cannot be excited to continue or interrupt the loop.