Given below are two statements: one is labelled Assertion(A) and other is labelled Reason(R).

Assertion(A): The excitation of one myocardial cell results in the excitation of other myocardial cells, making the entire muscle to contract as one unit.
Reason (R): Intercalated discs are the communication junctions at some fusion points which allow the cells to contract as a unit.

In the light of above statements, choose the correct answer from the options given below.

Assertion (A): The excitation of one myocardial cell results in the excitation of other myocardial cells, making the entire muscle contract as one unit. This phenomenon is known as functional syncytium. The cardiac muscle cells are interconnected by specialized junctions called intercalated discs.

Reason (R): Intercalated discs are the communication junctions found in cardiac muscle tissue. These discs contain gap junctions that allow the passage of ions and small molecules between adjacent cells. This direct electrical coupling enables action potentials to spread quickly from one cell to another. As a result, the excitation initiated in one cell rapidly spreads throughout the interconnected cells, leading to coordinated contraction of the entire cardiac muscle.

Both (A) and (R) are correct and (R) explains (A).