Final answer:
The speed at which the motor neuron fires is known as the frequency of motor neuron stimulation, affecting the muscle contraction strength, with wave summation or complete tetanus occurring depending on the stimulation frequency.
Step-by-step explanation:
The speed at which the motor neuron fires is known as the frequency of motor neuron stimulation. The rate at which a motor neuron fires action potentials is crucial because it affects the tension produced in the skeletal muscle. A single action potential results in a single muscle contraction, referred to as a twitch. When muscle fibers are stimulated successively without fully relaxing, the contractions sum up in a process known as wave summation, leading to a greater contraction. If the frequency of stimulation is so high that the muscle does not relax at all between stimuli, it results in complete tetanus, which is a continuous contraction.
Muscle contraction is controlled by the release of acetylcholine at the neuromuscular junction, triggering a muscle action potential that leads to calcium release and the sliding filament model of contraction. Significant factors such as motor neuron firing frequency, muscle twitch phases, and the presence of calcium ions act together to modulate the muscle's response to neuronal inputs.