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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 ...
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] Myokines are secreted into the bloodstream after muscle contraction.
A tetanic contraction (also called tetanized state, tetanus, or physiologic tetanus, the latter to differentiate from the disease called tetanus) is a sustained muscle contraction [2] evoked when the motor nerve that innervates a skeletal muscle emits action potentials at a very high rate.
Skeletal muscle, is a type of striated muscle, composed of muscle cells, called muscle fibers, which are in turn composed of myofibrils. Myofibrils are composed of sarcomeres, the basic building blocks of striated muscle tissue. Upon stimulation by an action potential, skeletal muscles perform a coordinated contraction by shortening each sarcomere.
Diagram of skeletal muscle fiber structure. Skeletal muscle cells are the individual contractile cells within a muscle and are more usually known as muscle fibers because of their longer threadlike appearance. [10] Broadly there are two types of muscle fiber performing in muscle contraction, either as slow twitch or fast twitch .
In physiology, medicine, and anatomy, muscle tone (residual muscle tension or tonus) is the continuous and passive partial contraction of the muscles, or the muscle's resistance to passive stretch during resting state. [1] [2] It helps to maintain posture and declines during REM sleep. [3]
In skeletal muscle, contraction is stimulated by electrical impulses transmitted by the motor nerves. Cardiac and smooth muscle contractions are stimulated by internal pacemaker cells which regularly contract, and propagate contractions to other muscle cells they are in contact with.