Sliding Filament Theory
The sliding filament theory describes the mechanism that allows muscles to contract.
According to this theory, myosin (a motor protein) binds to actin. The myosin then alters its configuration, resulting in a "stroke" that pulls on the actin filament and causes it to slide across the myosin filament.
The overall process shortens the sarcomere structure, but does not change the actual length of either filament.
Myofibrils run the entire length of the muscle fibre, and because they are only approximately 1.2 µm in diameter, hundreds to thousands can be found inside one muscle fibre.
They attach to the sarcolemma at their ends, so that as myofibrils shorten, the entire muscle cell contracts
•ATP binds to a myosin head, which is released from an actin filament
•Hydrolysis of ATP cocks the myosin head
•The myosin head attaches to an actin binding site with the help of Calcium
•The power stroke slides the thin filament when ADP and Pi are released from it
•350 myosin heads per thick filament
•Can bind and unbind to thin filament up to 5 X per second
Sliding Filament Theory in AWESOME Detail
