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Troponin complex

Tropomysin

SURE 18-6 Tropomyosin molecules The actin filament, composed of two /helical strands of

F-actin and tropomyosin molecules that fit loosely in the grooves "between the actin strands

Attached to one end of each tropomyosin molecule troponin complex that initiates

contraction. (Redrawn fiom Guyton A ^QOOk ofmedKOl physiotogy Philadelphia. 1996

Saunders, with permission )

h. producing limb motion Concentric contractions wncn the muscle shortens Eccentric

contractions r when the muscle lengthens More fast-twitch fibers are recruited during

eccentric contractions. Isokinetic confectionsoccur when muscle contraction is performedat a instant velocity. 1 his can be done only with the assistance preset rate-limiting device

This type of exercise does | exist in nature. KmtraM.nd inorganic phosphate. D, The release of stored energy from

step A provides the force needed for each cross-bridge to move back to its original position, fluiling actin along with it. E ach cross-bridge will remain bound to actin until another

ATP binds to It and pulls it back to lis resting position (A). (Redrawn from Kjbodeau GA Patton KT: Anorony andphysiology. St Louis. 1999. Mosby. with permission.)