Which of the following type of muscles are not fatigued soon

Options

A. Cardiac muscle
B. Smooth muscle
C. Both A and B
D. Voluntary muscle.

Answer

**Step-by-Step Solution:**

1. **Understanding Muscle Fatigue**:
- Muscle fatigue refers to the decline in the ability of a muscle to generate force. This occurs when muscles are overused or worked for extended periods, leading to a decrease in performance.

2. **Types of Muscles**:
- There are three main types of muscles in the human body: skeletal muscle, cardiac muscle, and smooth muscle. Each type has different characteristics and functions.

3. **Characteristics of Cardiac and Smooth Muscles**:
- Cardiac muscle is found in the heart and is responsible for pumping blood throughout the body.
- Smooth muscle is found in the walls of hollow organs (like the intestines and blood vessels) and helps in involuntary movements.

4. **ATPase Activity**:
- The rate of ATPase activity (the enzyme that hydrolyzes ATP to release energy) is crucial for muscle contraction.
- Cardiac and smooth muscles have myosin with a much slower ATPase activity (10 to 100 times slower) compared to skeletal muscle.

5. **Reason for Resistance to Fatigue**:
- Due to the slower ATPase activity in cardiac and smooth muscles, they can sustain contractions for longer periods without fatiguing quickly. This is essential for their functions, such as continuously pumping blood or maintaining organ tone.

6. **Conclusion**:
- Since both cardiac and smooth muscles are characterized by their slower ATPase activity and resistance to fatigue, the correct answer to the question is "both A and B."

**Final Answer**: Both cardiac muscle and smooth muscle are not fatigued soon.

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