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Key Terms Chapter 10: Muscle Tissue

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    62661
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    acetylcholine (ACh)
    neurotransmitter that binds at a motor end-plate to trigger depolarization
    actin
    protein that makes up most of the thin myofilaments in a sarcomere muscle fiber
    action potential
    change in voltage of a cell membrane in response to a stimulus that results in transmission of an electrical signal; unique to neurons and muscle fibers
    aerobic respiration
    production of ATP in the presence of oxygen
    angiogenesis
    formation of blood capillary networks
    aponeurosis
    broad, tendon-like sheet of connective tissue that attaches a skeletal muscle to another skeletal muscle or to a bone
    ATPase
    enzyme that hydrolyzes ATP to ADP
    atrophy
    loss of structural proteins from muscle fibers
    autorhythmicity
    heart’s ability to control its own contractions
    calmodulin
    regulatory protein that facilitates contraction in smooth muscles
    cardiac muscle
    striated muscle found in the heart; joined to one another at intercalated discs and under the regulation of pacemaker cells, which contract as one unit to pump blood through the circulatory system. Cardiac muscle is under involuntary control.
    concentric contraction
    muscle contraction that shortens the muscle to move a load
    contractility
    ability to shorten (contract) forcibly
    contraction phase
    twitch contraction phase when tension increases
    creatine phosphate
    phosphagen used to store energy from ATP and transfer it to muscle
    dense body
    sarcoplasmic structure that attaches to the sarcolemma and shortens the muscle as thin filaments slide past thick filaments
    depolarize
    to reduce the voltage difference between the inside and outside of a cell’s plasma membrane (the sarcolemma for a muscle fiber), making the inside less negative than at rest
    desmosome
    cell structure that anchors the ends of cardiac muscle fibers to allow contraction to occur
    eccentric contraction
    muscle contraction that lengthens the muscle as the tension is diminished
    elasticity
    ability to stretch and rebound
    endomysium
    loose, and well-hydrated connective tissue covering each muscle fiber in a skeletal muscle
    epimysium
    outer layer of connective tissue around a skeletal muscle
    excitability
    ability to undergo neural stimulation
    excitation-contraction coupling
    sequence of events from motor neuron signaling to a skeletal muscle fiber to contraction of the fiber’s sarcomeres
    extensibility
    ability to lengthen (extend)
    fascicle
    bundle of muscle fibers within a skeletal muscle
    fast glycolytic (FG)
    muscle fiber that primarily uses anaerobic glycolysis
    fast oxidative (FO)
    intermediate muscle fiber that is between slow oxidative and fast glycolytic fibers
    fibrosis
    replacement of muscle fibers by scar tissue
    glycolysis
    anaerobic breakdown of glucose to ATP
    graded muscle response
    modification of contraction strength
    hyperplasia
    process in which one cell splits to produce new cells
    hypertonia
    abnormally high muscle tone
    hypertrophy
    addition of structural proteins to muscle fibers
    hypotonia
    abnormally low muscle tone caused by the absence of low-level contractions
    intercalated disc
    part of the sarcolemma that connects cardiac tissue, and contains gap junctions and desmosomes
    isometric contraction
    muscle contraction that occurs with no change in muscle length
    isotonic contraction
    muscle contraction that involves changes in muscle length
    lactic acid
    product of anaerobic glycolysis
    latch-bridges
    subset of a cross-bridge in which actin and myosin remain locked together
    latent period
    the time when a twitch does not produce contraction
    motor end-plate
    sarcolemma of muscle fiber at the neuromuscular junction, with receptors for the neurotransmitter acetylcholine
    motor unit
    motor neuron and the group of muscle fibers it innervates
    muscle tension
    force generated by the contraction of the muscle; tension generated during isotonic contractions and isometric contractions
    muscle tone
    low levels of muscle contraction that occur when a muscle is not producing movement
    myoblast
    muscle-forming stem cell
    myofibril
    long, cylindrical organelle that runs parallel within the muscle fiber and contains the sarcomeres
    myogram
    instrument used to measure twitch tension
    myosin
    protein that makes up most of the thick cylindrical myofilament within a sarcomere muscle fiber
    myotube
    fusion of many myoblast cells
    neuromuscular junction (NMJ)
    synapse between the axon terminal of a motor neuron and the section of the membrane of a muscle fiber with receptors for the acetylcholine released by the terminal
    neurotransmitter
    signaling chemical released by nerve terminals that bind to and activate receptors on target cells
    oxygen debt
    amount of oxygen needed to compensate for ATP produced without oxygen during muscle contraction
    pacesetter cell
    cell that triggers action potentials in smooth muscle
    pericyte
    stem cell that regenerates smooth muscle cells
    perimysium
    connective tissue that bundles skeletal muscle fibers into fascicles within a skeletal muscle
    power stroke
    action of myosin pulling actin inward (toward the M line)
    pyruvic acid
    product of glycolysis that can be used in aerobic respiration or converted to lactic acid
    recruitment
    increase in the number of motor units involved in contraction
    relaxation phase
    period after twitch contraction when tension decreases
    sarcolemma
    plasma membrane of a skeletal muscle fiber
    sarcomere
    longitudinally, repeating functional unit of skeletal muscle, with all of the contractile and associated proteins involved in contraction
    sarcopenia
    age-related muscle atrophy
    sarcoplasm
    cytoplasm of a muscle cell
    sarcoplasmic reticulum (SR)
    specialized smooth endoplasmic reticulum, which stores, releases, and retrieves Ca++
    satellite cell
    stem cell that helps to repair muscle cells
    skeletal muscle
    striated, multinucleated muscle that requires signaling from the nervous system to trigger contraction; most skeletal muscles are referred to as voluntary muscles that move bones and produce movement
    slow oxidative (SO)
    muscle fiber that primarily uses aerobic respiration
    smooth muscle
    nonstriated, mononucleated muscle in the skin that is associated with hair follicles; assists in moving materials in the walls of internal organs, blood vessels, and internal passageways
    somites
    blocks of paraxial mesoderm cells
    stress-relaxation response
    relaxation of smooth muscle tissue after being stretched
    synaptic cleft
    space between a nerve (axon) terminal and a motor end-plate
    T-tubule
    projection of the sarcolemma into the interior of the cell
    tetanus
    a continuous fused contraction
    thick filament
    the thick myosin strands and their multiple heads projecting from the center of the sarcomere toward, but not all to way to, the Z-discs
    thin filament
    thin strands of actin and its troponin-tropomyosin complex projecting from the Z-discs toward the center of the sarcomere
    treppe
    stepwise increase in contraction tension
    triad
    the grouping of one T-tubule and two terminal cisternae
    tropomyosin
    regulatory protein that covers myosin-binding sites to prevent actin from binding to myosin
    troponin
    regulatory protein that binds to actin, tropomyosin, and calcium
    twitch
    single contraction produced by one action potential
    varicosity
    enlargement of neurons that release neurotransmitters into synaptic clefts
    visceral muscle
    smooth muscle found in the walls of visceral organs
    voltage-gated sodium channels
    membrane proteins that open sodium channels in response to a sufficient voltage change, and initiate and transmit the action potential as Na+ enters through the channel
    wave summation
    addition of successive neural stimuli to produce greater contraction
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