HN220 Lecture Notes - Lecture 15: Myocyte, Troponin, Anatomical Terms Of Motion
Document Summary
The mechanics of skeletal muscle contraction: the twitch (shortening of an individual muscle fiber, factors affecting the force generated by individual muscle fibers, regulation of the force generated by the whole muscle, velocity of shortening. Isometric and isotonic twitches: contractile elements = sarcomeres, series elastic elements = connective tissue, tendons, force exerted by contracting muscle = tension, force opposing contraction (such as weight to be moved) = load. Isometric twitch contraction: length constant, contractile elements contract, generating tension, when load > tension, stretches series of elastic elements, muscle does not shorten, load not lifted. Isotonic twitch contraction: constant tension, when tension > load, load is lifted as muscle shortens. If muscle tension > load (resistance): muscle shortens (concentric contraction) If muscle tension < load (resistance: muscle lengthens (eccentric contraction) The twitch: normal muscle activity, some purely isometric contractions occur, purely isotonic contractions are rare, even if the load is constant, isometric precedes isotonic phase of contraction.
