Explain in detail the mechanism of muscle contraction
Answers
During muscle contraction, the laterally projecting heads (cross bridges) of the thick myosin myofilaments come in contact with the thin actin myofilaments and rotate on them. This pulls the thin myofilaments towards the middle of the sarcomere past the thick myofilaments. The Z lines come closer together and the sarcomere becomes shorter. Length of the A band remains constant. Myofilaments stay the same length. Free end of actin myofilaments move closer to the centre of the sarcomere, bringing Z lines closer together. I bands shorten and H zone narrows. A similar action in all the sarcomeres results in shortening of the entire myofibril, and thereby of the whole fibre and the whole muscle. A contracted muscle becomes shorter and thicker and its volume remains the same.
Events durings Muscle Contraction
This theory which is called the sliding filament theory proposed by A.F. Huxley and J. Hansen is the most satisfactory and accepted one.
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Calcium is released from the sarcoplasmic reticulum at the time of muscle contraction ....
This calcium binds with Stark troponin I tropomyosin Complex on the actin filament molecules
the complex shifts and the myosin binding sites on actin filaments are exposed ...
Myosin head have actin binding sites as well as ATP sites..
Myosin head binds with the actin filaments and hydrolysis of ATP takes place that pushes the thin actin over the thick myosin filament ...
The thin filaments slide over the thick filament according to sliding filament theory...
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