Describe the role of calcium in muscle contraction, where it is stored, and how it is released and recycled. Calcium storage, release, and recycling
Muscles need to be malleable or have plasticity in order to function correctly. This is where calcium comes into the picture. All muscles use calcium molecules for regulatory and signaling purposes. Contraction control and relaxation control by calcium is achieved first by the activation of troponin-tropomyosin with the actin filaments. The second activation is the calcium with calmodulin which activates myosin light-chain kinase that initiate the contraction of the muscle (Berchtold, Brinkmeier, & Muntener, 2000). The sarcoplasmic reticulum (SR) is where the calcium is stored, released, and recycled within the skeletal muscles. According to Rossi & Dirksen (2006), the balance of the storage, release, and recycling of the required calcium is achieved by the cooperative actions of sarcoplasmic reticulum calcium-regulatory proteins. These proteins are as follows: Calcium storage—calsequestrin and junctate which are a calcium binding proteins along with sarcalumenin (Rossi & Dirksen, 2006). Calsequestrin is stored in the cisternae. Release of calcium—sarcoplasmic reticulum release channels, RyR1 and IP3 receptors (Rossi & Dirksen, 2006). At this step, ions of calcium are released into the sarcoplasm making the muscle contract (Martini & Nath, p. 298). Calcium recycling—Sarco(endo)plasmic reticulum calcium2+ and -ATPase or SERCA pumps (Rossi & Dirksen, 2006). This step is done via the terminal cisternae in the SR. Skeletal muscle fibers pump calcium ions out of their cells via transport through the plasma membranes as many cells do. However, in skeletal muscle fibers, it is a bit different. The skeletal muscle fibers use active transport removal of calcium ions via the terminal cisternae that are in the sarcoplasmic reticulum (Martini & Nath, 2009, p. 298). References:
Berchtold, M.W., Brinkmeier, H., & Muntener,...
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