Final answer:
When a muscle contraction fuses into a single continuous peak with no visible relaxation, it exhibits complete tetanus, a state of maximal tension due to rapid, successive nerve stimuli.
Step-by-step explanation:
When a stimulus is applied to a muscle in such a manner that each contraction wave fuses into a single continuous peak, the muscle is exhibiting complete tetanus.
In the body, muscles achieve graded muscle responses by varying the frequency of action potentials from motor neurons. When the frequency of stimulation is so high that the individual muscle twitches overlap, leading to a sustained contraction without any visible relaxation between twitches, summation occurs. If the frequency continues to increase, the muscle enters a state of complete tetanus, where the maximal tension is sustained continuously without relaxation phases.
This state results from a rapid series of nerve impulses delivering frequent and successive stimuli, causing a rise in intracellular calcium levels, which in turn facilitates continuous cross-bridge formation between actin and myosin within the muscle fibers.