Final answer:
An isotonic contraction refers to a muscle contraction in which the muscle length changes, while the muscle tension remains the same. This type of contraction can be either concentric or eccentric. In contrast, an isometric contraction refers to a muscle contraction in which muscle tension increases, but muscle length remains the same. Complete tetanus is a smooth, sustained contraction that occurs when the relaxation phase disappears due to high-frequency motor neuron signaling.
Step-by-step explanation:
An isotonic contraction refers to a muscle contraction in which the muscle length changes, but the muscle tension remains the same. This type of contraction occurs when a load is moved as the length of the muscle changes. There are two types of isotonic contractions: concentric and eccentric contractions.
Concentric contraction involves the muscle shortening to move a load, such as when the biceps brachii muscle contracts to bring a hand weight upward. On the other hand, an eccentric contraction occurs as the muscle tension diminishes and the muscle lengthens, such as when the hand weight is lowered in a controlled manner.
In contrast, an isometric contraction refers to a muscle contraction in which muscle tension increases, but muscle length remains the same. In this type of contraction, the muscle does not change its length, but the tension in the muscle increases.
Regarding the term complete tetanus, it refers to a smooth, sustained contraction of a muscle that occurs when the frequency of motor neuron signaling is so high that the relaxation phase disappears completely. This leads to continuous contractions.