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MedicineCardiology

Sequence of sarcomere contraction

THE CONTEXT
Sarcomere shortening follows exposure of the actin-binding site and a change in the angle of attachment of the myosin head.

Three stages of contraction

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Initially, tropomyosin blocks the actin-binding site.
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ATP-dependent release of calcium ions allows calcium to bind to troponin, displacing tropomyosin and exposing the binding site.
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Tilting of the angle of attachment of the myosin head results in fibre shortening.

Abbreviations

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ATP denotes adenosine triphosphate; ADP denotes adenosine diphosphate.
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