Final answer:
Gap junctions enable action potentials to spread across cardiac muscle cells, facilitating synchronized contraction and ensuring the heart operates as a unified functional syncytium. The correct option is b.
Step-by-step explanation:
Gap junctions are a vital part of the intercellular connection of cardiac muscles because they allow action potentials to spread to connected cells, which is necessary for the coordinated contraction of the heart muscle. These junctions form channels between adjacent cardiac muscle fibers that enable the depolarizing current produced by cations to flow from one cardiac muscle cell to the next. This process is referred to as electric coupling and is essential in the transmission of action potentials across cardiac tissues, leading to the synchronized contraction of the heart. Moreover, gap junctions contribute to forming a functional unit of contraction called a syncytium, which is crucial for the heart to function as a singular unit.