Sliding Filament Theory
Start with the big picture
The lesson connects sarcomere structure with the molecular events of contraction. It explains how the I band and H zone change while the A band remains constant, and how calcium binding to troponin allows myosin to access actin’s binding sites. The cross-bridge cycle links ATP binding and hydrolysis to myosin detachment, head activation, and the power stroke. It also introduces excitation–contraction coupling, calcium release and reuptake, and structural proteins that support sarcomere function. Finally, the topic relates muscle mechanics to length–tension and force–velocity relationships, and places selected clinical examples in context. Together, these concepts show how filament interaction, calcium, and energy use produce and regulate contraction.
What you'll learn
- Describe how actin and myosin movement changes sarcomere length and band regions.
- Explain how calcium and troponin regulate access to actin’s myosin-binding sites.
- Outline the ATP-dependent steps of the cross-bridge cycle.
- Summarize excitation–contraction coupling and calcium reuptake.
- Distinguish isometric and isotonic contractions and relate load to shortening velocity.
Continue your study
Work through the complete notes and reinforce the topic with the study tools available in the full lesson.
