How are cardiac action potentials conducted in both nodal and non-nodal tissues?

How are cardiac action potentials conducted in both nodal and non-nodal tissues?

• A. Through gap junctions only
• B. By cell-to-cell propagation
• C. Via extracellular diffusion
• D. By single fast conducting cells only

Answer: (B)

The key idea is that electrical impulses move through the heart by neighboring cells passing current to each other through gap junctions, making the tissue behave like a continuous syncytium. When a cell depolarizes, ions flow through gap junction channels into adjacent cells, triggering their depolarization and creating a wavefront that travels through both nodal (pacemaker) tissue and non-nodal (working myocardium) areas. This networked cell-to-cell propagation, not a single fast-conducting cell or extracellular diffusion, explains how the impulse spreads across the heart, albeit at different speeds in nodal versus non-nodal regions due to differences in gap junction expression and cell properties.

The key idea is that electrical impulses move through the heart by neighboring cells passing current to each other through gap junctions, making the tissue behave like a continuous syncytium. When a cell depolarizes, ions flow through gap junction channels into adjacent cells, triggering their depolarization and creating a wavefront that travels through both nodal (pacemaker) tissue and non-nodal (working myocardium) areas. This networked cell-to-cell propagation, not a single fast-conducting cell or extracellular diffusion, explains how the impulse spreads across the heart, albeit at different speeds in nodal versus non-nodal regions due to differences in gap junction expression and cell properties.