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Skeletal, Cardiac, and Smooth Muscle Physiology

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이 집합의 용어 (19)

  • Levels of organization in skeletal muscle

    Skeletal muscle is organized into muscle fibers grouped into fascicles, surrounded by connective tissues: endomycium, perimysium, and epimysium.

  • Sliding filament theory of muscle contraction

    Muscle contraction occurs as actin filaments slide over myosin filaments, shortening the sarcomere without changing filament length.

  • Excitation-contraction coupling

    Action potential triggers Ca2+ release from the sarcoplasmic reticulum, enabling myosin to bind actin and start the contractile cycle.

  • Contractile cycle steps

    1. Myosin binds actin forming cross-bridge.
    2. Power stroke pulls actin.
    3. ATP binds myosin, releasing it.
    4. ATP hydrolysis resets myosin head.

  • Causes of muscle fatigue

    Muscle fatigue can result from ATP depletion, lactic acid buildup, ion imbalances, or impaired neural stimulation.

  • Slow-twitch muscle fibers

    Slow-twitch fibers contract slowly, have high endurance, rich in mitochondria and myoglobin, and rely on aerobic metabolism.

  • Fast-twitch oxidative-glycolytic fibers

    These fibers contract quickly, use both aerobic and anaerobic metabolism, and have moderate resistance to fatigue.

  • Fast-twitch glycolytic fibers

    Fastest contracting fibers, rely on anaerobic glycolysis, fatigue quickly, and have fewer mitochondria and myoglobin.

  • Effect of muscle length on contraction force

    Optimal muscle length allows maximal overlap of actin and myosin, producing greatest force; too stretched or too contracted reduces force.

  • Summation in muscle contraction

    Summation occurs when multiple stimuli increase contraction strength by adding twitches before relaxation completes.

  • Types of tetanus

    Incomplete tetanus has partial relaxation between stimuli; complete tetanus has sustained contraction with no relaxation.

  • Motor unit definition

    A motor unit consists of a single motor neuron and all the muscle fibers it innervates, enabling graded muscle contractions.

  • Graded contractions in skeletal muscle

    Muscle force is varied by changing the number of active motor units and the frequency of stimulation.

  • Isometric contraction

    Muscle generates force without changing length, such as holding a weight steady.

  • Isotonic contraction

    Muscle changes length while generating force, including concentric (shortening) and eccentric (lengthening) contractions.

  • Smooth muscle anatomy

    Smooth muscle cells are spindle-shaped, lack striations, and contain actin and myosin arranged irregularly.

  • Smooth muscle twitch cycle

    Contraction is slower and sustained, regulated by Ca2+ binding to calmodulin activating myosin light chain kinase.

  • Differences between cardiac and skeletal muscle

    Cardiac muscle is striated, involuntary, has intercalated discs for electrical coupling, and contracts rhythmically.

  • Differences between cardiac and smooth muscle

    Cardiac muscle is striated and involuntary; smooth muscle is non-striated and controls slow, sustained contractions.