How can summation of skeletal muscle twitches occur if the motor neuron's refractory period prevents multiple action potentials from being transmitted to the neuromuscular junction at the same time?

Question

Quizplus · Accepted Answer

The motor neuron's absolute refractory period is shorter than the time required for calcium release and reuptake, allowing multiple action potentials to stimulate the muscle before calcium levels return to baseline, leading to summation.

How Can Summation of Skeletal Muscle Twitches Occur If the Motor