Module 3: Normal Anatomy And Physiology Of Muscle Contraction

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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
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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, permanent cross bridges are formed and rigor mortis occurs in the muscles (Nicholls State Univ).
II. Skeletal Muscle Fibers
There are three types of skeletal muscle fibers: slow oxidative (Type I), fast oxidative, (Type IIA), and fast glycolytic (Type IIB). The classifications are based on
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Muscular System.” Handy Anatomy Answer Book. Visible Ink Press. MI, USA. 2008 eISBN: 9781578592326
Brooks, Arthur. “Muscular and Skeletal System.” Systems of Our Global Media. Delhi, India. 2007 eISBN: 9788189940829
Keynes, RD, and Aidley, DJ. Nerve and Muscle: Chapter 7: Neuromuscular junction, Chapter 9: Skeletal muscles, and Chapter 10: The mechanism of contraction in skeletal muscle. Cambridge University Press, West Nyack, NY, USA. 2001 eISBN: 9781139147064
Kravitz, Len, Ph.D. “How Do Muscles Grow?” University of New Mexico. Accessed on 30 October, 2015 at http://www.unm.edu/~lkravitz/Article folder/musclesgrowLK.html
Nicholls State University; BIO 156 Lecture: Muscles. Accessed on 30 October 2015 at http://www.nicholls.edu/biol-ds/Biol156/Lectures/muscles 2.pdf
Ulrich, Daniel, Dr., Trinity College Dublin; Allied Health Science Physiology, Muscle Physiology. Accessed on 30 October 2015 at

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