Myosin and actin are filamentous protein molecules contained in muscles. In the presence of calcium ions (bottom), myosin and actin will slide past each other and form cross-bridges, thereby contracting the muscle.
Source: Chung, M.K., and Rich, M.W. Introduction to the cardiovascular system. Alcohol Health and Research World 14(4):269–276, 1990.
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Prepared: February 2001