muscle contraction

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muscle contraction

The movement of muscle fibres in response to force or load. 

Muscle contraction types 
• Concentric—The muscle shortens in length as it overcomes resistance.
• Eccentric—The muscle increases in length to accommodate resistance.  
• Isometric—The muscle resists outside stress without exhibiting motion.
Types of skeletal muscle contraction.

muscle contraction

the process of force-generation in the fibres of any class of muscle, by the interaction of myosin head-groups in the thick filaments with actin molecules in one of the immediately neighbouring thin filaments. This is set in train ('activated') by a rise in the concentration of calcium ions [Ca2+] in the muscle fibre cytoplasm in all types of muscle, but the mechanism for this rise differs in important respects between them. With reference to skeletal muscle, 'contraction', though literally implying shortening, is used to describe force-generation, whether it actually results in shortening (concentric action), tension without movement (isometric action) or even lengthening against the muscle's own resistance (eccentric action); the last is sometimes called an 'eccentric contraction' or, even worse, a 'lengthening contraction' - paradoxical usages better avoided. See also excitation-contraction coupling, force-velocity relationship, myofibrils.

muscle contraction

; voluntary muscle contraction; muscle twitch tension generated within muscle tissue, due to actin/myosin interaction, during which muscle length shortens, lengthens or remains unchanged (contrast with concentric muscle contraction, below); see agonist; antagonist; insertion; fixator; origin; synergist
  • concentric muscle contraction acceleration force generated within contracting agonist muscle tissue, by actin/myosin interaction; agonist muscle force overcomes antagonist muscle resistance, creating a net reduction in length of agonist muscle (see entry above)

  • eccentric muscle contraction deceleration force generated by interaction of actin/myosin of contracting antagonist muscle tissue; antagonist muscle force is insufficient to overcome agonist muscle resistance, creating a net increase in length of antagonist muscle

  • isometric muscle contraction muscle contraction that increases muscle tension, whilst maintaining constant overall muscle length; characteristic of e.g. intrinsic foot muscles which stabilize the toes against the support surface during weight-bearing, and the overall muscle length remains constant despite increasing muscle tension

  • isotonic muscle contraction muscle contraction with overall shortening of muscle length, in response to applied load, characteristic of e.g. leg muscles when lifting a heavy weight, using a combination of balanced concentric and eccentric contractions within limb, back and abdominal muscle groups; maximal generated muscle force is greater than total applied load

contraction

a drawing together; a shortening or shrinkage.

isovolumetric contraction
ventricular muscle contraction during early systole after closure of the atrioventricular valves and before the semilunar valves open; the muscle continues to contract, forcing up the ventricular pressure without any change in the ventricular volume.
muscle contraction
see muscle.
myocardial contraction
individual myocardial cells transmit motor impulses across cell boundaries and act as a syncytium.
contraction phase
the stage in wound healing when there is centripetal movement of surrounding tissues and the area of the wound decreases. This is believed to be a cell-mediated phenomenon, involving myofibroblasts.
postural contraction
the state of muscular tension and contraction that just suffices to maintain the posture of the body.
striated muscle contraction
see muscle.
tetanic contraction, tonic contraction
sustained muscular contraction with alternating relaxation.
References in periodicals archive ?
Pretranslational markers of contractile protein expression in human skeletal muscle: Effect of limb unloading plus resistance exercise.
These age-related changes in myosin and other contractile proteins, in conjunction with alterations in calcium transit and action potential, actually help the older heart work more efficiently.
Once released from this cellular storage bin, calcium binds to troponin and other contractile proteins, which trigger the heart beat.
The genes with differential expression included genes related to inflammation, cell cycle regulation, mitogenesis, signal transduction pathways, metabolism, and muscle contractile proteins.
The scientists suggest that the contractile proteins within these unusual cells pull on external fibers that are attached to the long, spiraling inner-ear structure called the basilar membrane.
These findings suggest that a fundamental metabolic shift toward anaerobic metabolism in hemiparetic skeletal muscle is accompanied by abnormalities in gene expression for muscle contractile proteins, inflammatory mediators, cell cycling, and signal transduction.
The cloned myocytes were functionally competent, expressed contractile proteins, and were electrically and mechanically coupled to other heart cells.
Some actin assembly-regulating proteins (thymosins, moesin, Arp 2/3) were also up-regulated, while muscle contractile proteins were either up-regulated ([alpha]-cardiac myosin heavy chain, atrial myosin light chain 1) or down-regulated (titin, tropomyosin 4, troponin I, etc).
myocyte hypertrophy, increased expression of contractile proteins, and myocardial hibernation [101.
After the clinical diagnosis was established, residual tissue samples from 13 patients with PM and 6 patients with DMD were stored frozen at -80[degrees]C until immunohistochemistry or extraction of contractile proteins.