Final answer:
Increasing the frequency of motor neuron stimulation results in the muscle generating more tension. This is caused by the successive twitches summing up and leading to greater muscle contraction. Higher stimulation frequencies also result in the release of more calcium ions, which activates additional sarcomeres and allows for a more forceful muscle contraction.
Step-by-step explanation:
When the frequency of motor neuron stimulation increases, the muscle generates more tension. This is because higher stimulation frequencies cause successive twitches to summate, resulting in greater muscle contraction. If the stimulation frequency becomes so high that the relaxation phase disappears completely, the muscle undergoes continuous contractions known as complete tetanus.
The increase in tension with higher stimulation frequencies is due to the release of more calcium ions, which activates additional sarcomeres and allows for a more forceful muscle contraction.