Anatomy And Physiology Of Muscle Contraction Essay

828 Words Nov 1st, 2015 4 Pages
Module 3: The Muscular System
I. Normal Anatomy/Physiology of Muscle Contraction
According to the sliding filament theory of muscle contraction, Hugh Huxley and Andrew Huxley determined that contractile proteins slide past each other to shorten the muscle (Handy Anatomy, pg 98). Muscle contraction is a complex series of chemical changes inside the muscle cell. For a muscle to contract, the muscle fiber is stimulated and calcium ions are released. The calcium ions move to the middle of the sarcomere. The sarcomere is the microscopic area in the middle of the muscle fiber, which is made of actin and myosin. The calcium ions bind to the troponin on the actin, causing the myosin head to be exposed. The actin and the now exposed myosin head then bind together. Adenosine triphosphate (ATP) becomes attached to the second binding site on the myosin. ATP is then hydrolyzed into ADP, which frees up a molecule of phosphate. The molecule of phosphate is released from the myosin head and the actin is pulled closer to the M-line of the sarcomere. The separation activates the myosin head, forming the cross-bridge to actin. The cross bridge is formed by the actin being pulled into the space between the myosin. The ADP is then released, which causes the myosin head to change back to the original position and separate from the actin. Multiple rounds of this occur at different myosin heads, resulting in a shortening of the sarcomere. ATP is required for muscle contraction. Without ATP,…

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