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Smooth muscle contraction is caused by the sliding of myosin and actin filaments (a sliding filament mechanism) over each other. The energy for this to happen is provided by the hydrolysis of ATP.
During a concentric contraction, a muscle is stimulated to contract according to the sliding filament theory. This occurs throughout the length of the muscle, generating a force at the origin and insertion, causing the muscle to shorten and changing the angle of the joint.
Aug 14, 2023 · Actin and myosin act as the main proteins involved in muscle contraction. Actin filaments attach to dense bodies spread throughout the cell. Dense bodies can be observed under an electron microscope and appear dark. Another important structure is the calcium-containing sarcoplasmic reticulum, which aids in sustaining contraction.
THE CONTRACTILE MECHANISM. In the intact body, the process of smooth muscle cell contraction is regulated principally by receptor and mechanical (stretch) activation of the contractile proteins myosin and actin.
‘The mechanisms of Ca 2+ mobilization in smooth muscle cells of the circular and longitudinal muscle layers vary. In muscle cells from both layers, G protein-coupled agonists initiate contraction by increasing cytosolic Ca 2+, or [Ca 2+] i.
We describe here a number of pathways by which vascular smooth muscle contraction and stiffness are directly regulated and hence will affect blood pressure.
Aug 4, 2003 · Contraction of smooth muscle is initiated by a Ca2 -mediated change in the thick filaments, whereas in striated muscle Ca2 mediates contraction by changes in the thin filaments.
Jul 1, 2003 · The activation of the smooth muscle cell is proposed to trigger dynamic remodeling of the actin filament lattice within cellular microdomains in response to local mechanical and pharmacological events, enabling the cell to adapt to its external environment.
Apr 9, 2024 · Contraction of smooth muscle is not under conscious control, hence it is referred to as an involuntary muscle. Triggers for smooth muscle contraction include hormones, neuronal stimulation by the autonomic nervous system and other local factors.
Mechanisms that regulate smooth-muscle contraction and relaxation. (A) Regulation by Ca 2 + -calmodulin: as intracellular Ca 2 + increases, excess Ca 2 + is bound by calmodulin, and the Ca 2 + -calmodulin complex binds to and activates myosin light chain (LC) kinase.
