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BIOL 1410 (94)

Muscular System

4 Pages

Biological Sciences
Course Code
BIOL 1410
Jennifer Mcleese

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Muscular System  Skeletal muscle system  Primarily attached to bone  Movement by contracting giving off heat Skeletal Muscle  Cells called fibers Fascicle: Groups of fibers Muscle: Group of fascicles Fascia = CT Epimysium: Surrounds entire muscle Perimysium: Surrounds fascicles Endomysium: Surrounds each muscle fiber Tendons + Aponeurosis  Extensions of epi, peri and Endomysium  Anchors to bone (periosteum) cartilage, skin or fascia of other muscles Tendon: Rope like (Achilles) Aponeurosis: Sheet like (Galea aponeurotica) Skeletal Muscle Fiber Structure  Large multinucleate cells Sarcolemma: Cell membrane Sarcoplasm: Cytoplasm Myofibrils (intracellular structures): Hundreds-thousands, composed of sarcomeres Sarcomere  2 types of myofilaments/proteins Thin filaments: Made of actin (contraction) Tropomysin + Troponin regulate contraction Thick Filaments  Myosin for contraction  Attached to Z discs by titin (protein)  Has tail with 2 globular heads (head extends toward actin and forms crossbridge)  Myofilaments create dark and light bands/striations of the sarcomere  Banding pattern: A Band: Length of thick filaments - myosin + actin (with troponin and tropomyosin) H Zone: Lighter band at center of A Band myosin only I Band: Light=actin (with troponin and tropomyosin) and titin Z Disc: Proteins in center of I Band, actin and titin attach, connect sarcomeres M Line: Myosin tail connect to each other (center of sarcomere)  Sarcomeres join end to end at Z discs to form myofibrils Dark: A band where myofilaments overlap Light: No overlap, H zone myosin only, I band actin only T-tubules  Parts of sarcolemma that extend deep into fiber/cell  Directly encircle myofilaments of myofibrils t junction of A and I bands (2/sarc) Sarcoplasmic Reticulum (SR)  Smooth ER Triad: 2 enlarged areas of SR (terminal cisternae) and T-tubule
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