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 ?
Phenytoin administration reduced muscle contractions in a time-dependent manner by both direct and indirect stimulations.
The sliding filament theory of skeletal muscle contraction can explain the shortening of a single sarcomere, but when we consider multiple sarcomeres in a myofibril arranged in series, it fails to justify the movement of Z discs as each Z disc is being pulled in the opposite direction by myosin heads of adjacent sarcomeres.
The results indicate that magnolol inhibits colonic smooth muscle contraction through its inhibition of the L-type [Ca.
32) and the presence or absence of sternocleidomastoid muscle contraction monitoring (p = 0.
Contrast aerobic to anaerobic metabolism during muscle contraction.
Participants were directed to perform a pelvic floor muscle contraction using a standardised instruction: 'Draw in through your pelvic floor muscles as best as you can whilst breathing normally'.
In free static stretching there is no external loading with muscle relaxation, or with isometric muscle contraction (sometimes called active static stretching).
This accelerated rate of muscle contraction will result in quicker movements on the playing field.
Vascular smooth muscle contraction is triggered primarily by a rise in intracellular free [Ca.
Concentric muscle contraction is defined by active shortening of the muscles, as in stepping upward.
Interventions: Prior to randomization, all women received individual instruction in pelvic floor anatomy, and had a correct pelvic floor muscle contraction confirmed on vaginal examination.
In myasthenia gravis, antibodies block, alter, or destroy the receptors for acetylcholine at the neuromuscular junction that prevents the muscle contraction from occurring.