When a neural signal reaching the neuromuscular junction releases acetylcholine, an action potential is generated first in

Options

A. Sarcolemma
B. Sarcoplasmic reticulum
C. Sarcosomes
D. Sarcomeres

Answer

To solve the question "When a neural signal reaching the neuromuscular junction releases acetylcholine, an action potential is generated first in," we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Neuromuscular Junction (NMJ)**:
- The neuromuscular junction is the synapse or junction between a motor neuron and a muscle fiber. It is where the nerve signal is transmitted to the muscle to initiate contraction.

2. **Role of Acetylcholine**:
- When a neural signal reaches the NMJ, it triggers the release of the neurotransmitter acetylcholine (ACh) from the motor neuron into the synaptic cleft.

3. **Action Potential Generation**:
- The binding of acetylcholine to receptors on the muscle fiber's membrane (sarcolemma) leads to depolarization of the muscle cell membrane. This depolarization is what generates an action potential.

4. **Identifying the Location of Action Potential Generation**:
- The action potential is first generated in the **sarcolemma**, which is the plasma membrane of the muscle fiber. The sarcolemma is critical for transmitting the action potential along the muscle fiber.

5. **Conclusion**:
- Therefore, the correct answer to the question is that the action potential is generated first in the **sarcolemma**.

### Final Answer:
The action potential is generated first in the **sarcolemma**.

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