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Muscle Web - The Muscular System how we move 3 Types of...

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The Muscular System – how we move 3 Types of muscle
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Muscle-related = myo-, mys-, sarco- (muscle cells = fibers) Muscle fibers (cells) come wrapped in connective tissue = endomysium (2 more layers in skeletal = perimysium and epimysium)
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Smooth Muscle Characteristics Figure 6.2a Found mainly in the walls of hollow organs Usu. in 2 layers; longitudinal and circular Move food, empty bowels and bladder
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Cardiac Muscle is arranged in spirals Figure 6.2b intercalated discs bind muscle cells, lots of gap junctions for communication Only in heart
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Skeletal Muscle is voluntary Most attached by tendons to bones Movement, generate body heat, maintain posture, stabilize joints
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Epi-, peri-, and endomysium, fuse to form tendons and aponeuroses… Figure 6.1 Tendons— cord-like structures (collagen fibers) Tough enough to cross joints Attach muscle to bone Aponeuroses— sheet-like tendons
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Microscopic Anatomy of Skeletal Muscle Sarcolemma— specialized plasma membrane of muscle cell/fiber Myofibrils— long contractile organelles of muscle cell
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Myofibril proteins account for striations I band = light band Contains only thin filaments (actin) A band = dark band Contains thick (myosin) and thin (actin) filaments
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Sarcomere = contractile unit of myofibril (bordered by z disc membranes that anchor actin) Figure 6.3b
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Myosin filaments have myosin heads that engage actin to contract…. Figure 6.3d What the…???? But HOW?!?!? Myosin heads
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Muscles are stimulated by motor neurons (nerve cells) Motor unit — 1 motor neuron + all its muscle cells
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Neuromuscular junctions = nerve cell + muscle fiber Acetylcholine (Ach) = Neurotransmitter that activates muscle cell Activated sarcolemma = flood of Na+ into the cell
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