Final answer:
A high-frequency burst of action potentials resulting in continuous muscle contractions is called tetanus. Wave summation leads to this condition, and when the stimulus frequency is very high and eliminates the relaxation phase, complete tetanus occurs.
Step-by-step explanation:
A high-frequency burst of action potentials resulting in continuous contractions is known as tetanus. Wave summation occurs when the excitation-contraction coupling effects of successive motor neuron signaling are added together. If the stimulus frequency reaches a point where the relaxation phase is eliminated, the muscle contractions become continuous, a condition referred to as complete tetanus. In complete tetanus, the tension in the muscle is about three to four times greater than that of a single twitch and does not allow for any relaxation between contractions.
The refractory period prevents another action potential from being initiated while one is in progress. During this time, the voltage-sensitive ion channels return to their resting configurations, which is essential for the proper function of neurons and muscles. Hyperpolarization occurs when the membrane potential is more negative than the normal resting potential, which happens during the refractory period after an action potential.