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* Acetylcholine * Actin * ATP * Ca+ ions * Myosin heads * * Na+/K+ ions * Troponin * Tropomyosin * Sarcoplasmic reticulum * Z-line

* Binds to sarcolemma * Opens Na+/K+ gated ion channels *

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Pulled by myosin

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Attaches to Z-line

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* Energizes the power stroke of myosin head * Disconnects the myosin cross bridge from the binding site on actin. * Fuels the pump that actively transports calcium ions back into the sarcoplasmic reticulum. *

* Bind to troponin * Help expose binding sites on actin *

* Powered by ATP, pull actin filaments closer together *

* Depolarize muscle cell * Cause Ca+ ions to leave sarcoplasmic reticulum *

* Binds to tropomyosin * When Ca+ present, helps slide tropomyosin off binding sites *

* Covers binding sites on actin where myosin heads bind *

* Storage of Ca+ ions * Released during depolarization *

* Pulled together during contraction * Attached to actin myofilaments *

* Click here to see a quick animation review… *

* Acetylcholine * Actin * ATP * Ca + ions * Myosin heads * * Na + /K + * Troponin ions * Tropomyosin * Sarcoplasmic reticulum * Z-line