Question

action potentials spreading along the sarcolemma of a muscle fiber result from the opening of ____ channels in the sarcolemma.

sodium
calcium
potassium

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Explanation:

When action potentials spread along the sarcolemma of a muscle fiber, it is due to the opening of sodium channels. Sodium ions rush into the cell, depolarizing the membrane and initiating the action - potential process. Calcium channels are important for muscle contraction but not for the initial spread of the action potential along the sarcolemma. Potassium channels are mainly involved in repolarization after the action potential.

Answer:

A. sodium