How do skeletal muscles contract according to the sliding filament theory?

The correct answer involves understanding the sliding filament theory, which describes the mechanism of muscle contraction at the microscopic level. According to this theory, skeletal muscles contract through the interaction of actin and myosin filaments, which are the primary proteins responsible for muscle contraction.

During muscle contraction, myosin heads bind to actin filaments, forming cross-bridges. When the myosin heads pivot, they pull the actin filaments toward the center of the sarcomere, resulting in the shortening of the muscle fiber. This process requires ATP and is regulated by calcium ions released from the sarcoplasmic reticulum. The sliding filament theory explains how the sarcomeres, the functional units of muscle fibers, contract by sliding over each other rather than changing in length on their own.

This clear mechanism highlights the collaboration between the two types of filaments—actin and myosin—and their role in muscle contraction, which is fundamental to our understanding of how skeletal muscles function.