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Sliding filament theory: A sarcomere in relaxed (above) and contracted (below) positions. The sliding filament theory explains the mechanism of muscle contraction based on muscle proteins that slide past each other to generate movement. [ 1] According to the sliding filament theory, the myosin ( thick filaments) of muscle fibers slide past the ...
Depiction of smooth muscle contraction. Muscle contraction is the activation of tension -generating sites within muscle cells. [ 1][ 2] In physiology, muscle contraction does not necessarily mean muscle shortening because muscle tension can be produced without changes in muscle length, such as when holding something heavy in the same position. [ 1]
In a cAMP-dependent pathway, the activated G s alpha subunit binds to and activates an enzyme called adenylyl cyclase, which, in turn, catalyzes the conversion of ATP into cyclic adenosine monophosphate (cAMP). [ 5] Increases in concentration of the second messenger cAMP may lead to the activation of. an enzyme called protein kinase A (PKA).
Myofilament. Myofilaments are the three protein filaments of myofibrils in muscle cells. The main proteins involved are myosin, actin, and titin. Myosin and actin are the contractile proteins and titin is an elastic protein. The myofilaments act together in muscle contraction, and in order of size are a thick one of mostly myosin, a thin one of ...
All-or-none law. In physiology, the all-or-none law (sometimes the all-or-none principle or all-or-nothing law) is the principle that if a single nerve fibre is stimulated, it will always give a maximal response and produce an electrical impulse of a single amplitude. If the intensity or duration of the stimulus is increased, the height of the ...
The sarcoplasmic reticulum ( SR) is a membrane -bound structure found within muscle cells that is similar to the smooth endoplasmic reticulum in other cells. The main function of the SR is to store calcium ions (Ca 2+ ). Calcium ion levels are kept relatively constant, with the concentration of calcium ions within a cell being 10,000 times ...
NCBI. proteins. Flow of ions. Alpha and beta units. The sodium–potassium pump ( sodium – potassium adenosine triphosphatase, also known as Na+/K+-ATPase, Na+/K+ pump, or sodium–potassium ATPase) is an enzyme (an electrogenic transmembrane ATPase) found in the membrane of all animal cells. It performs several functions in cell physiology .
The energy stored between these bonds can then be transferred to do work. For example, the transfer of energy from ATP to the protein myosin causes a conformational change when connecting to actin during muscle contraction. [1] The cycle of synthesis and degradation of ATP; 1 and 2 represent output and input of energy, respectively.