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How Do Muscles Contract?
Describing what is occurring in the body for muscular contraction to occur.
Date : 02/09/2023
Muscular stimulation
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AP propagates along surface membrane and into T tubules
Electrical impulse stimulates release of Ca2+ ions from sarcoplasmic reticulum
Ca2+ binds to troponin and tropomyosin moves out of way
Reveals myosin binding site on actin
Ca2+ is actively transported into SR continuously while APs continue a
Myosin head of myosin filament can bind to exposed binding site
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Ca2+ binds to troponin and tropomyosin moves out of way
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This exposes myosin binding site on surface of actin chain
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`Charged` myosin heads bind to exposed site on actin filament
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This binding and discharge of ADP causes myosin head to pivot (the power stroke) which pulls actin filament towards centre of sarcomere (M line)
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ATP binds and releases myosin head from actin chain
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ATP hydrolysis provides energy to recharge the myosin head
This is process happens repeatedly across many sarcomeres and myofibres and the muscle shortens
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