Muscle Contraction: Understanding the Sliding Filament Theory
Sliding Filament Theory of Muscle Contraction
- Actin & myosin filaments: Thin (actin) and thick (myosin) protein filaments.
- Motor units: Motor neuron + muscle fibers; nerve signal releases neurotransmitters.
- Calcium release: From sarcoplasmic reticulum binds troponin on actin.
- Troponin shift: Moves tropomyosin, exposing myosin-binding sites on actin.
- Cross-bridge cycling: Myosin heads bind actin, hydrolyze ATP, perform power stroke (pull actin), release ADP/Pi.
- Relaxation: Calcium pumped back; tropomyosin blocks sites again.
Repeated cycles generate force, movement, posture. Nervous system coordinates motor units for precise control.
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