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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]
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 actin ( thin filaments ) during muscle contraction, while the two groups of filaments ...
It consists of two periods: one during which the heart muscle relaxes and refills with blood, called diastole, following a period of robust contraction and pumping of blood, called systole. [1] After emptying, the heart relaxes and expands to receive another influx of blood returning from the lungs and other systems of the body, before again ...
An isometric exercise is an exercise involving the static contraction of a muscle without any visible movement in the angle of the joint. The term "isometric" combines the Greek words isos (equal) and -metria (measuring), meaning that in these exercises the length of the muscle and the angle of the joint do not change, though contraction ...
The primary function of muscle is contraction. [3] Following contraction, skeletal muscle functions as an endocrine organ by secreting myokines – a wide range of cytokines and other peptides that act as signalling molecules. [62] Myokines in turn are believed to mediate the health benefits of exercise. [63]
The rapid influx of calcium into the cell signals for the cells to contract. When the calcium intake travels through an entire muscle, it will trigger a united muscular contraction. This process is known as excitation-contraction coupling. [2] This contraction pushes blood inside the heart and from the heart to other regions of the body.
As the muscle shortens while generating a tensile force (i.e. "pulling"), then, by convention, the muscle is said to be performing positive work ("acts as a motor") during that phase. As the muscle lengthens (while still generating a tensile force), the muscle is performing negative work (or, alternatively, that positive work is being performed ...
Consequently, this initial phase of ventricular systole is known as isovolumic contraction, also called isovolumetric contraction. [1] In the second phase of ventricular systole, the ventricular ejection phase, the contraction of the ventricular muscle has raised the pressure within the ventricle to the point that it is greater than the ...