Respuesta :
Rising sarcoplasmic calcium levels results in contraction in both smooth muscle fibers and skeletal muscle fibers is true.
In striated muscle, the sarcoplasmic reticulum (SR) is the primary intracellular calcium storage, and it is crucial for controlling the excitation-contraction coupling (ECC) and intracellular calcium concentrations during contraction and relaxation of muscle. By attaching to calmodulin and activating the enzyme myosin light chain kinase, calcium triggers the contraction of smooth muscle. Contractile activity results from the phosphorylation of myosin on the 20,000-dalton light chain by the active form of myosin light chain kinase. The membrane of the sarcoplasmic reticulum contains the pump. Sometimes it is so abundant that it may account for 90% of the protein there. The muscle can relax by pumping calcium ions back into the sarcoplasmic reticulum, which is propelled by ATP. This lowers the calcium concentration around the actin and myosin filaments.
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