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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 concentric contraction, muscle tension is sufficient to overcome the load, and the muscle shortens as it contracts. [8] This occurs when the force generated by the muscle exceeds the load opposing its contraction. During a concentric contraction, a muscle is stimulated to contract according to the sliding filament theory. This occurs ...
An example of normal spontaneous depolarization is the constant contractions of cardiac muscle, causing the heart to beat. Usually, intentional movement of the involved muscle causes fasciculations to cease immediately, but they may return once the muscle is at rest again. Tics must also be distinguished from fasciculations.
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 ...
An impulse from a nerve cell causes calcium release and brings about a single, short muscle contraction called a muscle twitch. If there is a problem at the neuromuscular junction, a very prolonged contraction may occur, such as the muscle contractions that result from tetanus. Also, a loss of function at the junction can produce paralysis. [5]
Tonic in physiology refers to a physiological response which is slow and may be graded. This term is typically used in opposition to a fast response. For instance, tonic muscles are contrasted by the more typical and much faster twitch muscles, while tonic sensory nerve endings are contrasted to the much faster phasic sensory nerve endings.
Within the muscle tissue of animals and humans, contraction and relaxation of the muscle cells is a highly regulated and rhythmic process. In cardiomyocytes, or cardiac muscle cells, muscular contraction takes place due to movement at a structure referred to as the diad , sometimes spelled "dyad."
It also initiates muscle contraction in skeletal and cardiac muscles and muscle relaxation in smooth muscles. Ca 2+ sparks are important in physiology as they show how Ca 2+ can be used at a subcellular level, to signal both local changes, known as local control, [3] as well as whole cell changes.