Final answer:
True, a skeletal muscle fiber contracts and shortens when stimulated, doing so through the sliding filament model of muscle contraction where actin and myosin filaments slide past each other.
Step-by-step explanation:
True, a skeletal muscle fiber is indeed an individual cell that contracts and shortens when stimulated. Skeletal muscle fibers are large, multinucleated cells with diameters of up to 100 µm and lengths reaching up to 30 cm. The plasma membrane, known as the sarcolemma, is essential for the conduction of action potentials that trigger muscle contraction.
Within these fibers are myofibrils, long cylindrical structures that contain protein filaments called actin and myosin. These myofibrils are responsible for muscle contraction through a process known as the sliding filament model of muscle contraction.
When signaled by a motor neuron, actin-myosin cross-bridges form inside the sarcomeres - the smallest contractile units of a muscle - causing them to shorten and thereby shortening the entire muscle fiber. This process generates the force necessary for skeletal movement. The strength of the contraction depends on the number of contracting fibers and the frequency of neural stimulation, with more fibers contracting simultaneously creating a greater force.