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Muscle Tissue and Contraction - Anatomy & Physiology

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  • Muscle with a striped appearance

    Striated muscle has a striped appearance due to the arrangement of actin and myosin filaments.

  • Element important in directly triggering muscle contraction

    Calcium ions (Ca²⁺) trigger muscle contraction by binding to troponin, exposing myosin-binding sites on actin.

  • Properties common to all three muscle tissues

    Excitability, the need for ATP, and elasticity are common properties of skeletal, cardiac, and smooth muscle tissues.

  • Correct order from smallest to largest unit in muscle tissue

    Myofibril, muscle fiber, fascicle, muscle is the correct order of muscle organization.

  • Meaning of sarcolemma depolarization

    Depolarization means the inside of the sarcolemma becomes less negative as sodium ions enter the cell.

  • Protein blocking myosin-binding sites on actin in relaxed muscle

    Tropomyosin blocks myosin-binding sites on actin when the muscle is relaxed.

  • When do binding sites on actin open according to the sliding filament model?

    Binding sites on actin open when calcium ions bind to troponin, causing tropomyosin to move.

  • Name of the muscle fiber cell membrane

    The muscle fiber cell membrane is called the sarcolemma.

  • How muscle relaxation occurs

    Muscle relaxation occurs when calcium ions are actively transported back into the sarcoplasmic reticulum.

  • When does the cross-bridge detach during muscle contraction?

    The cross-bridge detaches when ATP binds to the myosin head, allowing it to release actin.

  • Functional units of thin and thick filaments

    Thin and thick filaments are organized into functional units called sarcomeres.

  • Phase of a muscle twitch with greatest tension

    Tension is greatest during the contraction phase of a muscle twitch.

  • Cause of muscle fatigue

    Muscle fatigue is caused by exhaustion of energy reserves and buildup of lactic acid.

  • Why sprinters fatigue sooner than marathon runners

    Sprinters fatigue sooner due to anaerobic metabolism producing lactic acid faster.

  • Energy supply aspect of creatine phosphate

    Creatine phosphate supplies energy through high-energy phosphate bonds that regenerate ATP quickly.

  • Effect of a drug blocking ATP regeneration in muscle cells

    Muscle cells will use glycogen as an alternative energy source when ATP regeneration is blocked.

  • Muscle fiber composition in professional sprinters

    Sprinters typically have about 50% fast-twitch and 50% slow-twitch muscle fibers.

  • Muscle fiber composition in professional marathon runners

    Marathon runners usually have about 40% fast-twitch and 60% slow-twitch muscle fibers.

  • True statement about fast muscle fibers

    Fast fibers have a large diameter and densely packed myofibrils, enabling rapid contractions.

  • Difference between cardiac and skeletal muscles

    Cardiac muscles are striated and use aerobic metabolism, unlike some skeletal muscle fibers.

  • Characteristic of smooth muscle compared to skeletal and cardiac

    Smooth muscle is involuntary and lacks striations, differing from skeletal and cardiac muscle.

  • Embryonic origin of muscle tissue

    Muscle tissue develops from myoblast cells during embryonic development.

  • Cell type that repairs injured muscle fibers

    Satellite cells help repair and regenerate injured muscle fibers.