Contraction of Smooth Muscle

Contraction of Smooth Muscle
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Contraction of Smooth Muscle

Smooth muscle tissue can be found in the walls of many organs. Smooth muscle tissue does not have striated banding pattern found in skeletal and cardiac muscle. The autonomic nervous system, hormones, and chemical signals can trigger the smooth muscle to contract. Cross bridging of actin and myosin is used to create force with the calcium ion influx initiating contraction. There are two protein pathways namely, calmodulin driven kinase pathway and caldesmon driven pathway, that can contribute to contraction. These protein pathways are initiated by calcium influx. Study suggests that actin, myosin, and intermediate filaments may be more volatile than previously suspected. Changes in these cytoskeletal elements may contribute to the process of contraction. Smooth muscle contraction uses a variant of the same sliding filament model found in striated muscle. However, the actin and myosin in smooth muscle are anchored to focal adhesion, and dense bodies are spread over the surface of the smooth muscle cell. As actin and myosin move across one another, focal adhesion are drawn closer to the dense bodies which squeezes the cell into a smaller form. The sliding in smooth muscle is triggered by calcium-caldesmon binding. Myosin light chain phosphorylation is also involved in the triggering of effective contraction.


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