HP_C10Notes_Muscle Tissue.doc - Human Physiology Notes Chapter 10 – Muscle Tissue Muscle Function and Types Function Generate movement Generate force

HP_C10Notes_Muscle Tissue.doc - Human Physiology Notes...

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Human Physiology Notes Chapter 10 – Muscle Tissue Muscle Function and Types Function Generate movement Generate force Role in maintaining temperature (skeletal) Muscle Types Skeletal muscle Voluntary Striated Control body movement Cardiac muscle Involuntary Striated Found in heart Moves blood through circulatory system Smooth muscle Involuntary Not striated Muscle of internal organs (stomach, urinary bladder, blood vessels) Moves material through body Skeletal Muscle Skeletal muscle structure o Skeletal muscles attached to bone on each end by tendons o Tendons forms sheaths that extend around and into skeletal muscle o Connective tissue (tendons) divides muscle into columns called fascicles o Muscle fascicle = bundle of muscle fibers Skeletal muscle cells = muscle fibers o Muscle cells similar to other cells, but multinucleate and striated o Plasma membrane = sarcolemma o Cytoplasm = sarcoplasm o Modified endoplasmic reticulum = sarcoplasmic reticulum (SR) Ca ++ sequestered at terminal cisternae of SR T – tubules – membranous continuation of sarcolemma; closely associated with terminal cisternae of SR o Myofibrils 1
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Each muscle fiber packed with myofibrils Each myofibril packed with myofilaments Myofilaments are proteins that give rise to “striations” Actin – thin filaments Myosin – thick filaments Titin – huge elastic protein, returns muscle to resting length after contraction In a myofibril, there is a repeating pattern of alternating light and dark bands. One repeat = sarcomere Sarcomere – contractile unit of skeletal muscle consisting of components between two Z discs A band – dark band, contains thick filaments (mostly myosin) H band – light area at the center of A band, here actin and myosin do not overlap I band – light band that contains thin filaments (mostly actin) Z line/disc – zigzag proteins serving as attachment site for thin filaments M line – structural proteins that anchor myosin during contraction The neuromuscular junction o Somatic motor neuron meets and innervates muscle fiber o On the sarcolemma where NMJ occurs = motor end plate o Each motor neuron branches to innervate a variable number of muscle fibers o Motor unit = somatic motor neuron and all of innervated fibers o When activated, motor neuron causes contraction of muscle fibers in motor unit o Number of muscle fibers in motor unit varies according to degree of fine control Fine motor actions 1 motor neuron innervates a small number of fibers (muscles that move the eyes or hands – 1 motor neuron per 3 to 5 muscle fibers) Gross motor actions Motor unit may contain hundreds or thousands of fibers (muscles for standing and walking – gastrocnemius has about 2000 muscle fibers in each motor unit) Muscle Contraction 2
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Shortening occurs because thin filaments (actin) slide over and
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  • Fall '16
  • Dusti Sloan

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