nerve impulse reaches the axon terminal
acetylchline (ACh) is released from the axon terminal
ACh crosses the synaptic cleft
attaches to ACh receptors on the sarcolemma
sarcolemma becomes permeable to sodium (Na+), voltage gated sodium channels open
the sodium rushes in. voltage gated sodium channels close
the voltage gated potassium channels open. K rushes out. following this, the voltage gated potassium channels close
this movement of ions causes a depolarization and repolarization of the sarcolemma called an action potential
this action potential travels the length of the muscle fiber
once started, it cannot be stopped
the action potential travels to interior of muscle fiber by T tubules
this triggers the release of calcium ions from the sarcoplasmic reticulum
calcium binds to troponin on actin molecule
crossbridge forms between actin and mysin
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