The force a motor unit exerts depends on the rate at which the somatic motor neuron discharges action potentials because calcium is released from the sarcoplasmic reticulum faster than it is pumped back by the Ca²⁺-ATPase pump.

Question

Quizplus · Accepted Answer

This statement is true. The rate of action potential firing in the somatic motor neuron determines the amount of calcium released into the cytoplasm of the muscle cell. The faster the neuron fires, the more calcium is released, leading to a greater force of contraction. The Ca2+-ATPase pump then works to remove calcium from the cytoplasm, but it operates more slowly than the release of calcium, so the force of contraction will still depend on the rate of action potential firing.

The Force a Motor Unit Exerts Depends on the Rate