During muscle contraction

Options

A. 1)Mechanical energy is changed into chemical energy
B. 2)Chemical energy is changed into mechanical energy
C. 3)Chemical energy is changed into electrical energy
D. 4)Physical energy is changed into chemical energy

Answer

**Step-by-Step Solution:**

1. **Understanding Muscle Contraction**: Muscle contraction is a process that allows muscles to shorten and generate force. This process is essential for various bodily movements, including eating, walking, and other physical activities.

2. **Role of the Central Nervous System (CNS)**: The contraction of muscles is initiated by signals from the Central Nervous System (CNS). The CNS sends a signal to the muscles to contract.

3. **Chemical Signal - Acetylcholine**: The signal from the CNS is transmitted in the form of a chemical messenger known as acetylcholine. This chemical is released at the neuromuscular junction, which is the point where nerve cells connect with the muscles.

4. **Conversion of Energy**: When acetylcholine binds to receptors on the muscle fibers, it triggers a series of events that lead to muscle contraction. During this process, the chemical energy (from acetylcholine) is converted into mechanical energy, which results in the movement of the muscle.

5. **Analyzing the Options**:
- **Option 1**: Mechanical energies change into chemical energy - Incorrect.
- **Option 2**: Chemical energies change into mechanical energy - Correct.
- **Option 3**: Chemical energies change into electrical energy - Incorrect.
- **Option 4**: Physical energies change into chemical energy - Incorrect.

6. **Conclusion**: The correct answer is that during muscle contraction, chemical energies change into mechanical energy.

**Final Answer**: The correct option is **Option 2**: Chemical energies change into mechanical energy.

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