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Description
| Question | Answer |
| What happens to a contracting sarcomere? | The I-band shrinks - pulling the Z-line and A-band together - The H-zone also shrinks |
| What is Troponin? | Molecules that are bound to tropomyosin. Which contain calcium ion binding sites. |
| Where is Tropomyosin found? | It wound around the actin |
| What is the first stage of the Sliding Filament Theory? | Relaxed muscle - tropomyosin blocks the binding sites on the actin filaments. - prevents myosin and actin binding together, so contraction is impossible |
| What is the second stage of the Sliding Filament Theory? | Nerve impulses stimulate the release of calcium ions - from the sarcoplasmic reticulum |
| What is the third stage of the Sliding Filament Theory? | High concentrations - calcium ions bind to troponin. This causes the tropomyosin to change shape, exposing the actin binding sites |
| What is the forth stage of the Sliding Filament Theory? | The activated myosin heads bind to the actin filament, producing tension in the muscle |
| What is the fifth stage of the Sliding Filament Theory? | Binding to the actin causes myosin heads to change shape. Causing the whole filmanet to be pulled along the actin. - ADP is now released from myosin heads |
| What is the sixth stage of the Sliding Filament Theory? | ATP binds to the myosin heads. This is broken down to produce ADP, Pi and energy. Energy allows the myosin heads to release actin and return to original state |
| What is the seventh stage of the Sliding Filament Theory? | The cycle now repeats. - dragging the myosin filaments further along the actin - sarcomere will continue to contract if ATP is present |
| What is the eighth stage of the Sliding Filament Theory? | Calcium is actively removed for the sarcoplasm when the muscle no longer stimulates the nerve. Tropomyosin returns to original state. |
| What is the ninth stage of the Sliding Filament Theory? | Bridges are no longer formed between actin and myosin. With no force holding the fibres together, fibres are pulled apart by antagonistic muscle action |
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