Question by Tom: What is the signification of calcium to proper muscle contraction?
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What is the signification of calcium to proper muscle contraction?
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Answer by Peter S
1.An electrical signal (action potential) travels down a nerve cell, causing it to release a chemical message (neurotransmitter) into a small gap between the nerve cell and muscle cell. This gap is called the synapse.
2.The neurotransmitter crosses the gap, binds to a protein (receptor) on the muscle-cell membrane and causes an action potential in the muscle cell.
3.The action potential rapidly spreads along the muscle cell and enters the cell through the T-tubule.
4.The action potential opens gates in the muscle's calcium store (sarcoplasmic reticulum).
5.Calcium ions flow into the cytoplasm, which is where the actin and myosin filaments are.
6.Calcium ions bind to troponin-tropomyosin molecules located in the grooves of the actin filaments. Normally, the rod-like tropomyosin molecule covers the sites on actin where myosin can form crossbridges.
7.Upon binding calcium ions, troponin changes shape and slides tropomyosin out of the groove, exposing the actin-myosin binding sites.
8.Myosin interacts with actin by cycling crossbridges. The muscle thereby creates force, and shortens
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