Muscles that undergo contraction for long periods without fatigue are  

Options

A. 1. uninucleated muscles
B. 2. straited muscles
C. 3. muscles with intercalated discs
D. 4. all the above

Answer

To solve the question "Muscles that undergo contraction for long periods without fatigue are," we will analyze the options provided and understand the characteristics of different muscle types.

### Step-by-Step Solution:

1. **Understand Muscle Contraction**:
- Muscle contraction refers to the process where muscle fibers shorten or reduce in size to produce movement. This is a fundamental property of all muscle types.

2. **Identify the Options**:
- The options given are:
- A) Uninucleated muscles
- B) Striated muscles
- C) Muscles with intercalated discs
- D) All of the above

3. **Analyze Each Option**:
- **Option A: Uninucleated Muscles**:
- Uninucleated muscles have a single nucleus. These are typically smooth muscles, which can sustain contractions for longer periods without fatigue.
- **Option B: Striated Muscles**:
- Striated muscles (skeletal muscles) are responsible for voluntary movements and are not known for prolonged contractions without fatigue.
- **Option C: Muscles with Intercalated Discs**:
- These are cardiac muscles, which have intercalated discs that allow for synchronized contraction. While they can sustain contractions, they are not categorized as muscles that contract for long periods without fatigue.
- **Option D: All of the Above**:
- This option suggests that all previous types can sustain long contractions without fatigue, which is incorrect based on the analysis.

4. **Conclusion**:
- Based on the analysis, the correct answer is **Option A: Uninucleated Muscles**. These muscles can undergo contractions for long periods without fatigue.

### Final Answer:
Muscles that undergo contraction for long periods without fatigue are **uninucleated muscles**.

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