What provides electrical coupling between cardiac muscle cells?

• A. Gap junctions
• B. Desmosomes
• C. Intercalated discs
• D. Tight junctions

Answer: (A)

Electrical coupling in cardiac muscle is provided by gap junctions. These channels form direct cytoplasmic connections between neighboring cardiomyocytes, created by connexin proteins that link adjacent cell interiors. Because ions can pass through gap junctions, an electrical impulse that begins in one cell quickly spreads to its neighbors, producing the synchronized contraction that characterizes heart tissue. Gap junctions are located in the intercalated discs, the regions where cardiac cells meet. In contrast, desmosomes mainly provide mechanical adhesion to hold cells together during strong contractions, and tight junctions seal spaces between cells but do not enable electrical communication. Intercalated discs house both the mechanical and electrical junctions, with gap junctions specifically responsible for the rapid electrical coupling.