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The Sliding Filament Model

The Sacromere

The striped appearance of voluntary muscles is different when relaxed or contracted.

The span from one Z line to another Z line is one sacromere; in a relaxed state it is 2.5
µm long. Z lines are closer together during contraction because the length…

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In muscle contraction;

1. Myosin head groups attach to the surrounding actin filaments forming a

2. The head then bends, causing the thin filament to be pulled along and so
overlap more with the thick filament. This is the power stroke. ADP and Pi are

3. The cross-bridge…

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When there is no action potential; calcium ions are actively transported back into the
sarcoplasmic reticulum by carrier proteins. This leads to muscle relaxation.

The Role of ATP in The Power Stroke

When the myosin head attaches to the actin binding site and `bends', the molecules are in
their most…

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