Final answer:
The statement is false because the all-or-none law applies to individual skeletal muscle fibers and not to the muscle as a whole. Muscle contraction strength is controlled by recruitment and the sliding filament model of contraction. The length-tension relationship in sarcomeres influences the force of muscle contractions.
Step-by-step explanation:
False. While it's true that when a skeletal muscle fiber is stimulated, it contracts maximally, the statement as a whole is false because not all muscle fibers within a skeletal muscle will necessarily contract at the same time. This is due to the all-or-none principle, which applies to individual muscle fibers, not the entire muscle itself. When a muscle fiber receives a stimulus that is above a certain threshold, it will contract maximally. However, the number of fibers that contract determines the overall force of muscle contraction.
The nervous system employs a mechanism known as recruitment to control the strength of a muscle contraction. During recruitment, more motor units (each consisting of a motor neuron and its innervated muscle fibers) are activated to increase muscle tension. Muscle fibers contract fully thanks to a biological process called the sliding filament model of contraction.
The strength and duration of muscle contraction are also influenced by the length-tension range of a sarcomere—the structural unit of a myofibril in a skeletal muscle. The sarcomere's optimal length allows for the greatest number of cross-bridge formations between actin and myosin, which in turn results in strong muscle contractions. When sarcomeres contract, the muscle fibers shorten, and this all-or-none response of each fiber contributes to the overall graded response of the entire muscle.