Muscle Lecture

Muscle Lecture - TYPES OF MUSCLE TISSUE Skeletal muscle...

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TYPES OF MUSCLE TISSUE Skeletal muscle - associated with the skeleton striated (exhibits alternating dark and light bands) voluntary (innervated by the somatic nervous system and subject to voluntary control). Cardiac muscle - occurs in the wall of the heart striated and involuntary (innervated by the autonomic nervous system - contractions not under conscious control) Smooth muscle - found in the walls of hollow organs and tubes (blood vessels, stomach, and I ntestines) nonstriated and involuntary
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Types of Vertebrate Muscle Tissue
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STRUCTURE OF SKELETAL MUSCLE: A single skeletal muscle cell ( muscle fiber) is formed by fusion of undifferentiated, mononucleated cells (myoblasts) , into a single, cylindrical, multinucleated fiber Muscle fibers do not divide Each fiber is covered by a plasma membrane (sarcolemma) Muscle fibers are arranged in bundles called fasciculi , to form the muscle Skeletal muscle fibers contain cylindrical myofibrils , each consisting of alternating light and dark bands (I-bands and A- bands), respectively The bands of all the myofibrils lined up parallel to each other, accounts for the striated appearance of a skeletal muscle fiber
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ORGANIZATION OF SKELETAL MUSCLE
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ORGANIZATION OF THE MYOFIBRIL Consists of - thick filaments , composed of the protein myosin thin filaments , made up primarily of the protein actin and smaller amounts of the proteins tropomyosin and troponin Thick and thin filaments are specifically arranged in contractile units called sarcomeres , which are the basic functional units of striated muscle fibers. Z discs - narrow zones of dense material which separate sarcomeres. A band - dark area consisting of a stacked set of thick filaments along with the portions of the thin filaments that overlap on both ends of the thick filaments. I band - light area consisting of the portion of thin filaments that do not project into the A band.
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THICK FILAMENTS ARE COMPOSED OF MYOSIN Each myosin molecule consists of 2 identical golf club- shaped molecules with their tails intertwined and their globular heads projecting at one end:
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ARRANGEMENT OF MYOSIN MOLECULES INTO THICK FILAMENTS The myosin heads project outward on the surface of the shaft of the thick filament forming cross bridges During muscle contraction these cross bridges make contact with the thin filaments and exert force on them The cross bridges are the force-generating sites in muscle cells
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This note was uploaded on 08/15/2011 for the course PHYSCI 3 taught by Professor Cooper during the Spring '11 term at UCLA.

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Muscle Lecture - TYPES OF MUSCLE TISSUE Skeletal muscle...

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