The muscles that are innervated by somatic nervous system undergo fatigue  

Options

A. quickly
B. randomly
C. slowly
D. never

Answer

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks about the muscles that are innervated by the somatic nervous system and whether they undergo fatigue quickly, randomly, slowly, or never.

2. **Identifying the Somatic Nervous System**: The somatic nervous system is responsible for controlling voluntary movements by innervating skeletal muscles. It is distinct from the autonomic nervous system, which controls involuntary functions.

3. **Understanding Muscle Fatigue**: Muscle fatigue refers to the decline in the ability of a muscle to generate force. It occurs when the muscle is unable to maintain its expected power output during prolonged activity.

4. **Role of Motor Neurons**: Motor neurons transmit signals from the brain to the skeletal muscles. During voluntary muscle activity, these neurons fire repeatedly to control the timing and strength of muscle contractions.

5. **Factors Leading to Fatigue**: Fatigue can occur when the firing of motor neurons is impeded. This means that if the signals from the brain to the muscles are disrupted or slowed down, the muscles will not contract effectively, leading to fatigue.

6. **Evaluating the Options**:
- **Quickly**: Muscles can indeed fatigue quickly during intense or prolonged activity.
- **Randomly**: Fatigue does not occur randomly; it is usually linked to the intensity and duration of activity.
- **Slowly**: While some fatigue can build up over time, the question implies a more immediate response.
- **Never**: Muscles cannot function indefinitely without fatigue.

7. **Conclusion**: Based on the understanding of muscle fatigue and the role of the somatic nervous system, the correct answer is that the muscles innervated by the somatic nervous system undergo fatigue **quickly**.

**Final Answer**: The muscles that are innervated by the somatic nervous system undergo fatigue **quickly**.

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