Which statement describes a requirement for sustaining a reentry circuit?

Which statement describes a requirement for sustaining a reentry circuit?

• A. A Single Homogeneous Pathway Without Any Refractory Variation
• B. Parallel Pathways That Are Connected Proximally And Distally, Forming A Circuit
• C. Simultaneous Conduction With Identical Refractory Periods
• D. Absence Of Conduction Delay

Answer: (B)

A reentry circuit needs a closed loop of conducting tissue around an obstacle, with two parallel routes that can form a circuit. This setup allows the impulse to travel around the loop, and then, once tissue ahead has recovered from refractoriness, to re-enter and continue circulating. The described arrangement—two parallel pathways connected at both ends to form a loop—provides exactly that looping pathway: one part can conduct while the other is blocked or slower, creating the conditions for the wavefront to re-enter after recovery and sustain the circuit. The other possibilities lack this looping architecture or the necessary timing differences: a single homogeneous pathway has no circuit for reentry; simultaneous conduction with identical refractory periods eliminates the differential block needed for a loop; and no conduction delay removes the time window for recovery that allows re-entry to persist.

A reentry circuit needs a closed loop of conducting tissue around an obstacle, with two parallel routes that can form a circuit. This setup allows the impulse to travel around the loop, and then, once tissue ahead has recovered from refractoriness, to re-enter and continue circulating. The described arrangement—two parallel pathways connected at both ends to form a loop—provides exactly that looping pathway: one part can conduct while the other is blocked or slower, creating the conditions for the wavefront to re-enter after recovery and sustain the circuit.

The other possibilities lack this looping architecture or the necessary timing differences: a single homogeneous pathway has no circuit for reentry; simultaneous conduction with identical refractory periods eliminates the differential block needed for a loop; and no conduction delay removes the time window for recovery that allows re-entry to persist.