What is functional syncytium?

• A. A single isolated cell
• B. A cluster of nondisparate cells
• C. Current leakage sequence repeated among excitable adjacent cells thereby conducting the electrical impulse
• D. A state of complete electrical isolation

Answer: (C)

Functional syncytium describes how cardiac muscle behaves as a coordinated unit because adjacent myocytes are electrically coupled. Through gap junctions at intercalated discs, ions flow directly from one cell to the next, so when one cell depolarizes, its neighbors depolarize in quick succession. This electrotonic spread creates a wave of depolarization that propagates through the tissue, coordinating contraction of the atria and ventricles. It’s not an isolated cell, nor just a loose cluster, nor an electrically isolated state. The essence is that current leaks from excitable cell to adjacent excitable cells, propagating the impulse through the heart muscle.