Part 4/14:
Figure: The intricate internal structure of skeletal muscle, highlighting fibers, fascicles, sarcomeres, and the molecular components such as actin, myosin, titin, and tropomyosin.
Molecular Mechanics of Muscle Contraction
At the heart of muscle's ability to contract is the sliding filament theory, which explains how actin and myosin filaments slide past each other within sarcomeres, shortening the muscle. During contraction:
Myosin heads bind to actin filaments forming cross-bridges.
Using energy from ATP hydrolysis, myosin heads pivot, pulling actin filaments towards the center of the sarcomere.
The cycle repeats as long as calcium ions and ATP are present.
Key components involved:
- Myosin heads: Bind and hydrolyze ATP, generate power strokes.