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Muscle Physiology 1

More force number od thickthin filamentsareas

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Unformatted text preview: ell to onset of contraction (few msec) Excitation- contraction coupling Contraction phase (force phase, mass units) Time tension is increasing (10- 100 msec) Crossbridge cycling Relaxation phase Time tension is decreasing back to zero (longer than contraction phase) Ca2+ reuptake Isometric and Isotonic Twitch: Components of a Muscle Contractile elements: sarcomeres Elastic elemts are the connective tissue, tendons Force exerted by contracting muscle is the tension For FINISH Isometric: length is constant, all or nothing Contractile elements contract generating tension Load > tension, stretches series eleastic elemetns Muscle does not shorten, load not lifted (postural muscle when standing still) PHOTO Isotonic: tension is not constant, not all or nothing Tension > Load; when T =L, muscle begins to shorten Load is then lifted as muscle shortens Plateau phase tension muscle shortening Load falls with relaxation Frequency of Stimulation Muscles move from twitch, treppe, summation, tetanus Increase frequency AP in muscle fibers, what degree of separation At higher frequencies, rate of Ca2+ release from SR exceeds reuptake More Ca2+ in cytosol bount to troponin More myosin binding sites exposed on actin...
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