Which physiological process explains muscle contraction at the cellular level?

The sliding-filament theory is the process that accurately explains muscle contraction at the cellular level. This theory describes how muscle fibers contract by the interaction between two types of filaments within the muscle cells: actin (thin filaments) and myosin (thick filaments). During contraction, the myosin heads attach to binding sites on the actin filaments, pulling them closer together and shortening the sarcomere, which is the basic functional unit of skeletal muscle. This process is triggered by the presence of calcium ions and is regulated by proteins like troponin and tropomyosin.

The sliding-filament theory is fundamental to understanding how muscles generate force and movement, as it directly outlines the changes that occur within the muscle fibers during contraction. This framework helps explain various functional aspects of muscle activity, from gross movement to fine motor skills.

Other options, although related to muscle physiology, do not specifically describe the cellular mechanism of muscle contraction. Muscle hypertrophy refers to the increase in muscle size due to factors such as resistance training but does not explain the immediate process of contraction. Oxidative phosphorylation is a metabolic process for ATP production that fuels muscle activity but is not directly related to the contraction mechanism itself. The neuromuscular junction theory involves how