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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 muscle fibers belonging to one motor unit can be spread throughout part, or most of the entire muscle, depending on the number of fibers and size of the muscle. [2] [3] When a motor neuron is activated, all of the muscle fibers innervated by the motor neuron are stimulated and contract. The activation of one motor neuron will result in a ...
The definition and use of the term myokine first occurred in 2003. [5] In 2008, the first myokine, myostatin, was identified. [4] [6] The gp130 receptor cytokine IL-6 (Interleukin 6) was the first myokine found to be secreted into the blood stream in response to muscle contractions.
Myokines are secreted into the bloodstream after muscle contraction. Interleukin 6 (IL-6) is the most studied myokine, other muscle contraction-induced myokines include BDNF, FGF21, and SPARC. [64] Muscle also functions to produce body heat. Muscle contraction is responsible for producing 85% of the body's heat. [65]
The function of the antagonist muscle contraction is believed to control the amplitude and timing of ballistic movements. Antagonist muscle contraction may serve to prevent injury to joints by preventing the limb from overextending itself and also function to control the distance and time the limb is being moved.
The myofilaments act together in muscle contraction, and in order of size are a thick one of mostly myosin, a thin one of mostly actin, and a very thin one of mostly titin. [1] [2] Types of muscle tissue are striated skeletal muscle and cardiac muscle, obliquely striated muscle (found in some invertebrates), and non-striated smooth muscle. [3]
[1] [3] One muscle may be normal while the other is atrophic or hypertrophic; alternately, one muscle may be hypertrophic while the other is atrophic. [3] A decrease in muscle tone leads to continuous disuse and eventually muscular atrophy. The constant contraction of the agonist muscle with minimal resistance can result in a contracture.
Nerves in the peripheral nervous system spread out to various parts of the body, including muscle fibers. A muscle fiber and the motor neuron to which it is connected. [15] The spot at which the motor neuron attaches to the muscle fiber is known as the neuromuscular junction. When muscles receive information from internal or external stimuli ...