Answer :
Final answer:
As the frequency of motor neuron signaling increases, the muscle tension in the motor unit also increases until it reaches a peak. This state is known as incomplete tetanus. If the stimulus frequency is high enough, the muscle contractions become continuous in a process called complete tetanus (option d).
Explanation:
If the frequency of motor neuron signaling increases, summation and subsequent muscle tension in the motor unit continues to rise until it reaches a peak point. The tension at this point is about three to four times greater than the tension of a single twitch, a state referred to as incomplete tetanus.
During incomplete tetanus, the muscle goes through quick cycles of contraction with a short relaxation phase for each. If the stimulus frequency is so high that the relaxation phase disappears completely, contractions become continuous in a process called complete tetanus (Figure 10.16b).
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