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Chapter10 p 2

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Kathleen Cercone
Kathleen Cercone

This short document appears to be copyrighted material from Pearson Education discussing a multi-part series. However, it does not contain any actual content beyond copyright notices, so a meaningful summary cannot be generated from the information provided.

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? 2015 Pearson Education, Inc. Part 2
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? 2015 Pearson Education, Inc.
? 2015 Pearson Education, Inc.
Chapter10 p 2
Chapter10 p 2
Chapter10 p 2

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Chapter10 p 2

Editor's Notes

  • #10: What are three functions of ATP in muscle contraction? The sarcoplasmic reticulum membrane also contains Ca2+ active transport pumps that use ATP to move Ca2+ constantly from the sarcoplasm into the SR While muscle action potentials continue to propagate through the T tubules, the Ca2+ release channels are open. Calcium ions flow into the sarcoplasm more rapidly than they are transported back by the pumps. After the last action potential has propagated throughout the T tubules, the Ca2+ release channels close. As the pumps move Ca2+ back into the SR, the concentration of calcium ions in the sarcoplasm quickly decreases. Inside the SR, molecules of a calcium-binding protein, appropriately called calsequestrin (kal¡ä-se-KWES-trin), bind to the Ca2+, enabling even more Ca2+ to be sequestered or stored within the SR. As a result, the concentration of Ca2+ is 10,000 times higher in the SR than in the cytosol of a relaxed muscle fiber. As the Ca2+ level in the cytosol drops, tropomyosin covers the myosin-binding sites, and the muscle fiber relaxes.