Summary:
- Muscle contraction occurs when muscle fibers get shorter.
- To understand how this happens, you need to know more about the structure of muscle fibers.
- A muscle fiber either contracts fully or it doesn’t contract at all.
- The number of fibers that contract determines the strength of the muscular force.
- When more fibers contract at the same time, the force is greater.
- The most widely accepted theory explaining how muscle fibers contract is called the sliding filament theory.
- According to this theory, myosin filaments use energy from ATP to “walk” along the actin filament with their cross bridges.
- The movement of the myosins pulls the Z lines closer together, thus shortening the sarcomere.