SLIDING FILAMENT THEORY

ROLE OF CALCIUM IN THEORY

- When binding with the troponin, calcium changes its shape which in effect removes the blocking of tropmyosin which allows the myosin heads to attach to the actin.

- Calcium levels vary depending on the action - when muscle goes to rest the myosin head needs to deattach from the actin filament therefore calcium levels drop to allow the myosin head to move back to its original position.

SLIDING FILAMENT THEORY

- The sliding filament theory occurs in the sarcomeres, which run laterally along the myofibril.

- Each sarcomere is made up of two filaments, actin and myosin.

- When we decide to move, calcium attaches onto the troponin of the actin, this then changes shape causing topomyosin to move around allowing the myosin head to attach onto the actin.

- The attachment of the myosin head onto the actin is called a 'CROSS BRIDGE'.

- Once the connection is complete, the ATP allows the myosin head to push the actin, this is called the power stroke and causes the sarcomere to shorten.

- To disconnect the cross bridge, ADP allows the myosin head to return to its original position, this is called the recovery stroke.

- If there is still enough calcium the process will keep going until the calcium is transported back into the sarcopaslmic reticulum, therefore causing the muscle to relax.