Question

compare and contrast the mechanism of contraction and relaxation for skeletal vs. smooth muscle, focus on the source of Ca+2 and where the Ca+2 works. Be sure to include which proteins are modified and how that effects the binding of actin and myosin.

Answer 1

In smooth muscle contraction with the stimulus there opens the voltage gated channels of calcium and thus calcium reaches. Sarcoplasmic reticulum. Ca2+ then binds to calmodulin. Then activates myosin light kinase. This leads to the phosphorylation of myosin head and the myosin binds to the actin and form cross bridge. Here tropin is not present. Here the calcium sources are sarcoplasmic reticulum itself and the extracellular fluid from where the calcium reaches inside by Ca2+ channels.

In skeletal muscle when stimulus reaches the skeletal muscle the sarcoplasmic reticulum act as the source of Ca2+. The Ca2+ secreted via T tubules. Now the Ca2+ binds to troponin and thus the troponin blockage is removed from the actin. later the phosphorylation of the myosinr head occurs and thus allow myosin to bind to actin. Thus crossbridge is formed. Here we have troponin.