Points which are correct with respect to cardiac muscle ?
(i) Have dark and light bands
(ii) Involuntory in nature
(iii) Similar to smooth muscle in structure
(iv) Muscle fibres are branched, cylindrical
(v) get fatigued after a long period.

Options

A. (i), (ii), (iii)
B. (i), (ii), (iv)
C. (iii), (iv), (v)
D. (i), (iii), (v)

Answer

To determine which points are correct with respect to cardiac muscle, we will analyze each statement one by one.

1. **Have dark and light bands**:
- Cardiac muscle fibers contain both dark (A bands) and light (I bands) bands due to the arrangement of actin and myosin filaments. This is a characteristic of striated muscles, which includes cardiac muscle.
- **Conclusion**: This statement is **correct**.

2. **Involuntary in nature**:
- Cardiac muscle operates involuntarily, meaning it is not under conscious control. The heart beats continuously without the need for conscious thought, which is essential for survival.
- **Conclusion**: This statement is **correct**.

3. **Similar to smooth muscle in structure**:
- Cardiac muscle is structurally different from smooth muscle. Smooth muscle fibers are spindle-shaped and unbranched, while cardiac muscle fibers are cylindrical, branched, and striated.
- **Conclusion**: This statement is **incorrect**.

4. **Muscle fibers are branched, cylindrical**:
- Cardiac muscle fibers are indeed branched and cylindrical. This branching allows for the interconnection of cardiac muscle cells, which is crucial for synchronized contractions of the heart.
- **Conclusion**: This statement is **correct**.

5. **Get fatigued after a long period**:
- Cardiac muscle is highly resistant to fatigue and is designed to work continuously throughout a person's life without tiring. If the heart were to fatigue, it would lead to severe health issues.
- **Conclusion**: This statement is **incorrect**.

### Summary of Correct Statements:
- The correct statements regarding cardiac muscle are:
1. Have dark and light bands (Correct)
2. Involuntary in nature (Correct)
3. Muscle fibers are branched, cylindrical (Correct)

Thus, the correct points with respect to cardiac muscle are **1, 2, and 4**.