If one cardiac muscle cell receives stimulus for contraction, neighbouring cardiac muscle cells are also stimulated due to  

Options

A. microvilli
B. sarcoplasmic reticulum
C. communication junctions
D. tight junctions

Answer

To answer the question, "If one cardiac muscle cell receives stimulus for contraction, neighbouring cardiac muscle cells are also stimulated due to," we will follow these steps:

### Step-by-Step Solution:

1. **Understanding Cardiac Muscle Structure**:
- Cardiac muscle cells are unique in their structure and function. They are branched and interconnected, allowing them to work together as a unit.

**Hint**: Think about how the structure of cardiac muscle cells contributes to their function.

2. **Identifying the Types of Junctions**:
- Cardiac muscle cells are connected by specialized structures known as intercalated discs. These discs contain various types of junctions, including gap junctions, which facilitate communication between cells.

**Hint**: Recall the different types of junctions found in tissues and their functions.

3. **Role of Communication Junctions**:
- The intercalated discs allow for the passage of ions and electrical signals between adjacent cardiac muscle cells. This means that when one cell is stimulated to contract, the electrical impulse can quickly spread to neighboring cells.

**Hint**: Consider how electrical signals can propagate through tissues and the importance of rapid communication in muscle contraction.

4. **Conclusion**:
- Therefore, the reason neighboring cardiac muscle cells are also stimulated when one cell receives a contraction stimulus is due to these communication junctions (intercalated discs). They enable the cells to contract synchronously, which is essential for the heart's function of pumping blood effectively.

**Hint**: Summarize the key function of intercalated discs in cardiac muscle contraction.

### Final Answer:
The correct answer is **communication junctions** (intercalated discs), as they allow for the propagation of the contraction stimulus from one cardiac muscle cell to its neighbors.