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10 10 07 - Muscular System I

10 10 07 - Muscular System I - Chapter 10 Muscles Types of...

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Chapter 10: Muscles Types of Muscles All muscles develop from mesoderm – myoblasts are migratory cells that differentiate into myocytes All have same contraction mechanism But have structural differences Construction Myoblasts fuse together and form one large cell forms a syncitium Syncitium- cell with multiple nuclei 3 types: Skeletal Muscle : Comprises all muscle in somatic part of body (skeleton) There are some exceptions Differentiation – myoblasts coalesce to form multinucleate muscle fibers – production of actin- and myosin -based myofibrils Stripes due to the multiple proteins inside Myofibril -component/organelle of muscle cell that is responsible for contraction 2 types of filaments make this up: 1. Actin 2. Myosin Activated by nerve impulse must be triggered Construction Myoblasts fuse together and form one large cell forms a syncitium Syncitium- cell with multiple nuclei Cardiac Muscle : Differentiation – cells branch to make connections with several other cardiomyocytes – cells form connections called intercalated discs that allow electrical connections – myofibrils much like skeletal muscle Activated by specialized muscle cells – pacemaker cells pacemaker cells may be modified by neruogenic stimuli pacemaker cells- stimulates all muscles connected to it does not need a nervous input to stimulate muscle but it can be used to modify the beat It is NOT a syncitium multiple cells Held together by gap junctions These junctions transmit impulse for contraction Therefore they still are able to act as a whole They branch no parallel arrangements
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