Which of the following is true about muscle physiology?

Options

A. A muscle fibres obey all-or-none law but not a muscle
B. A muscle obeys all-or-none law but not a muscle fibre
C. A muscle as well as muscle fibres obey all or-none law
D. Neither muscles nor muscle fibres obey all or-none law

Answer

**Step-by-Step Solution:**

1. **Understanding Muscle Physiology**: Muscle physiology refers to the study of how muscles function, particularly during movement. It involves understanding the changes that occur in muscle fibers when they contract in response to stimuli.

2. **Identifying the All or None Law**: The all or none law states that a muscle fiber will respond fully to a stimulus or not at all. This means that if the stimulus is above a certain threshold, the muscle fiber will contract completely; if it is below that threshold, there will be no contraction.

3. **Evaluating the Statements**:
- **Option 1**: "A muscle fiber obeys the all or none law, but not an overall muscle." This statement is true because individual muscle fibers respond according to the all or none principle, while the overall muscle can have varying degrees of contraction based on the number of fibers activated.
- **Option 2**: "Muscles obey the all or none law but not muscle fibers." This is false because muscle fibers do obey the all or none law.
- **Option 3**: "A muscle as well as muscle fibers obey the all or none law." This is incorrect because while muscle fibers do, overall muscles do not strictly obey this law.
- **Option 4**: "Neither muscle nor muscle fiber obey the all or none law." This is also false since muscle fibers do obey this law.

4. **Conclusion**: The only true statement regarding muscle physiology is the first option: "A muscle fiber obeys the all or none law, but not an overall muscle."