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32 Cards in this Set
- Front
- Back
What are the three major functions of the skeletal muscles?
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(a) endomysium, (b) perimysium, (c) epimysium
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Name some features of the muscle cell that are not found in other types of cells
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Excitability, contractibility, and extensibility
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What causes the striations observed in skeletal muscle fibers?
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The striations r a result of the A bands of sarcomeres appearing as relatively wide, dark stripes under the microscope, which alternate with narrower, lighter colored stripes formed by the I bands
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Why is the triad relationship between T tubules and the SR important
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The triad allows an electrical impulse traveling along a T tubule to stimulate the membranes of adjacent sacs of the SR
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Describe the structure of thin and thick myofilaments, and name the kinds of proteins that compose them
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Thin filament (actin, troponin,& tropomyosin): molecules strung 2gether like beads 2 form 2 fibrous strands that twist around each other.
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Describe the structure of thin and thick myofilaments, and name the kinds of proteins that compose them
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Thick filament (myosin): shaped like golf clubs,w/ their long shafts bundled together 2 form a thick filament & their “heads” sticking out from the bundle
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What is the role of calcium ions (Ca++) in muscle contraction?
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Calcium ions released from the SR bind to troponin in the thin filament allow tropomyosin 2 shift frm its position blcking the active sites of actin molecules, thus initiating the chemical reactions that produce contractions
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Where does the energy stored in ATP come from?
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Catabolism of foods
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What is the role of myoglobin in muscle fibers?
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Myoglobin attracts oxygen molecules and holds them temporarily. When the oxygen concentration inside a muscle fiber decreases rapidly, it can be quickly resupplied from the myoglobin
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What are the three phases of a twitch contraction?
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Latent period, contraction phase, and relaxation phase
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What is tetanus? Is it normal?
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tetanus is a smooth, sustained contraction. Yes, tetanus is the kind of contraction exhibited by normal skeletal muscle organs most of the time
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What is meant by the term muscle tone?
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Muscle tone (tonic contraction) is a continual, partial contraction in a muscular organ
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Name four factors that influence the strength of a skeletal muscle contraction
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Metabolic condition of individual muscle fibers, recruitment of motor units, length-tension relationship, amount of load imposed on the muscle
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What is meant by the phrase “recruitment of motor units
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Number of muscle fibers activated
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How do slow, separate, autorhythmic contractions of cardiac muscle make it well suited to its role in pumping blood?
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Cardiac muscle does not normally run low on ATP and thus does not experience fatigue
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What produces the striations in cardiac muscle?
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Each myofibril comprises sarcomeres that give the whole fiber a striated appearance
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How are myofilaments arranged in a smooth muscle fiber?
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Thin arrangements of myofilaments crisscross the cell and attach at their ends to the cell’s plasma membrane.
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Isometric contraction
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type of muscle contraction in which muscle does not alter the distance between two bones; see isotonic contraction
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Isotonic contraction
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type of muscle contraction in which the muscle sustains the same tension or pressure and a change in the distance between two bones occurs
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Motor unit
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functional unit composed of a single motor neuron with the muscle cells it innervates
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Muscle tone
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tonic contraction; characteristic of muscle of a normal individual who is awake
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Myofibril
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very fine longitudinal fibers found in skeletal muscle cells; composed of thick and thin filaments
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Myofilament
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ultramicroscopic, threadlike structures found in myofibrils; composed of myosin (thick) and actin (thin)
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Neuromuscular Junction
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point of contact between nerve endings and muscle fibers; see motor endplate
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Sarcolemma
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plasma membrane of a striated muscle fiber
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Sarcomere
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contractile unit of muscle cells; length of a myofibril between two Z disks
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Sarcoplasm
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cytoplasm of muscle fibers
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Sarcoplasmic reticulum
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network of tubules and sacs in muscle cells; similar to endoplasmic reticulum of other cells
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T Tubules
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transverse tubules unique to muscle cells; formed by inward extensions of the sarcolemma that allow electrical impulses to move deeper into the cell
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Tetanus
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smooth, sustained muscular contraction caused by high-frequency stimulation
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Threshold Stimulus
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minimal level of stimulation required to cause a muscle fiber to contract
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Anatomy & Physiology Chapter 11 Physiology of the Muscular System
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Anatomy & Physiology Chapter 11 Physiology of the Muscular System
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