Question

Do you agree or disagree with the following statement? Explain your answer.

When skeletal muscle receives a signal from the nervous system to contract, the signal from the motor neuron triggers the opening of a
voltage-sensitive Ca++ channel in the muscle cell plasma membrane, allowing Ca++ to flow into the cell.

Answer 1

The claimed statement is incorrect because calcium channels in the muscle cell plasma membrane are not directly triggered to open by a neural signal; it is the action potential resulting from acetylcholine binding that leads to Ca++ release from the SR, initiating muscle contraction.

Step-by-step explanation:

I do not agree with the statement. The signal from the motor neuron indeed triggers a muscle contraction, but it does not open voltage-sensitive Ca++ channels in the muscle cell plasma membrane directly. Instead, the released acetylcholine (ACh) binds to receptors on the sarcolemma (muscle cell membrane), which leads to depolarization and the subsequent opening of voltage-sensitive channels. This action potential then causes the release of calcium ions (Ca++) from the sarcoplasmic reticulum (SR) into the sarcoplasm to initiate contraction.