Cross Bridge
Muscular System
A cross-bridge is the temporary attachment of a myosin head to an actin filament and is the basic unit of force production in muscle.
The Cross-Bridge Cycle
- Ready state: the myosin head splits ATP into ADP and phosphate and enters a high-energy, “cocked” state.
- Attachment: once the binding site is exposed, the myosin head binds to actin.
- Power stroke: release of phosphate causes the myosin head to pivot, pulling actin towards the sarcomere centre by about 5–10 nanometres; ADP is then released.
- Detachment: binding of a new ATP to the myosin head releases it from actin.
- Re-cocking: ATP is split and the cycle repeats.
Key Points
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