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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]
Cardiac excitation-contraction coupling (Cardiac EC coupling) describes the series of events, from the production of an electrical impulse (action potential) to the contraction of muscles in the heart. [1] This process is of vital importance as it allows for the heart to beat in a controlled manner, without the need for conscious input.
[1] [2] These impulses ultimately stimulate heart muscle to contract and thereby to eject blood from the ventricles into the arteries and the cardiac circulatory system; and they provide a system of intricately timed and persistent signaling that controls the rhythmic beating of the heart muscle cells, especially the complex impulse-generation ...
Depolarization propagates through cardiac muscle very rapidly. Cells of the ventricles contract nearly simultaneously. The action potentials of cardiac muscle are unusually sustained. This prevents premature relaxation, maintaining initial contraction until the entire myocardium has had time to depolarize and contract. Absence of tetany.
It allows the motor neuron to transmit a signal to the muscle fiber, causing muscle contraction. [2] Muscles require innervation to function—and even just to maintain muscle tone, avoiding atrophy. In the neuromuscular system, nerves from the central nervous system and the peripheral nervous system are linked and work together with muscles. [3]
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 ...
Stretch of the muscle membrane opens a stretch-activated ion channel. The cells then become depolarized and this results in a Ca 2+ signal and triggers muscle contraction. No action potential is necessary here; the level of entered calcium affects the level of contraction proportionally and causes tonic contraction.
In the eccentric contraction, the muscles are involuntarily lengthened, while in the concentric contraction, the muscles are shortened after being tensed. Most of the stretching and shortening takes place in the tendons that attach to the muscles involved rather than in the muscles.