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As ATP is hydrolyzed to ADP and Pi, the myosin head returns to its prestroke high energy position

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After the ATP attached to the myosin, the link between myosin and actin weakens and myosin head breaks

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ADP and Pi are released and the myosin head pivots, changing to its bent low energy state which pulls the actin filament towards the M line

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Energized myosin head attaches to an actin myofilament forming a cross bridge

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The calcium combines with troponin and removes the blocking action of tropomyosin by changing the shape of actin so that the myosin binding sites are exposed. The myosin binds to actin and forms cross bridges and contraction begins.

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The transmission of the action potential along the t-tubules cause the adjacent sarcoplasmic reticulum to release calcium ions which flow into the cytosol

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The action potential moves down the sarcolemma and down the t-tubules

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The brain sends a neural impulse down to a neuromuscular junction. The nerve impulse causes voltage gated ion channels to open, this allows calcium ions to enter the neuron. The calcium stimulates the release of acetylcholine which is released into the synaptic cleft and absorbed by receptors in the axon terminal. The acetylcholine binds to receptors and activates voltage gated sodium channels which pump sodium ions in and potassium ions out of the membrane. More sodium is pumped is pumped in than potassium pumped out causing the cell interior to become less negative and causing depolarization and carrying the action potential down the sarcolemma. After the action potential, the voltage gated potassium channels open up which causes the membrane to become repolarized Summarize steps of event 1 using the following words: sarcolemma,