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Anatomy & Physiology: Muscle Tissue and Contraction

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Termini in questo insieme (30)

  • Types of muscle tissue

    Three types: skeletal (striated, voluntary), cardiac (striated, involuntary), and smooth (nonstriated, involuntary).

  • Skeletal muscle characteristics

    Long, striated fibers, voluntary control, responsible for body movement, rapid contraction but tires easily.

  • Cardiac muscle characteristics

    Found only in the heart, striated, involuntary, contracts without nervous stimulation, controlled by pacemaker cells.

  • Smooth muscle characteristics

    Found in walls of hollow organs, nonstriated, involuntary, slow and sustained contractions, controls movement of substances through organs.

  • Four special characteristics of muscle tissue

    Excitability, contractility, extensibility, and elasticity.

  • Functions of muscle tissue

    Produce movement, maintain posture, stabilize joints, and generate heat.

  • Connective tissue sheaths in skeletal muscle

    Epimysium surrounds whole muscle, perimysium surrounds fascicles, endomysium surrounds individual fibers.

  • Direct vs indirect muscle attachment

    Direct: epimysium fused to bone periosteum; Indirect: connective tissue extends as tendon or aponeurosis attaching muscle to bone or fascia.

  • Sarcoplasm contents

    Contains glycosomes (glycogen stores) and myoglobin (oxygen-binding pigment).

  • Myofibrils and sarcomeres

    Myofibrils are rodlike structures made of sarcomeres, the smallest contractile units between Z discs.

  • Striations in muscle fibers

    Alternating dark A bands and light I bands; A band contains H zone and M line; I band contains Z disc.

  • Thick and thin filaments

    Thick filaments contain myosin; thin filaments contain actin, tropomyosin, and troponin.

  • Role of troponin and tropomyosin

    Regulate contraction by blocking or exposing myosin-binding sites on actin in response to Ca2+.

  • Function of titin

    Elastic filament that stabilizes thick filaments and allows muscle to recoil after stretching.

  • Neuromuscular junction components

    Axon terminal, synaptic cleft, and junctional folds with ACh receptors on muscle fiber.

  • Events at neuromuscular junction

    Motor neuron releases ACh, which binds receptors causing end plate potential and triggers muscle action potential.

  • Excitation-contraction coupling

    AP travels along sarcolemma and T tubules, triggering Ca2+ release from sarcoplasmic reticulum, initiating contraction.

  • Sliding filament model

    Thin filaments slide past thick filaments, shortening sarcomeres without changing filament length.

  • Cross bridge cycle

    Myosin heads bind actin, pivot, detach using ATP, and reattach to pull thin filaments during contraction.

  • Muscle twitch phases

    Latent period (excitation-contraction coupling), contraction period (cross bridge activity), relaxation period (Ca2+ reuptake).

  • Temporal summation

    Increased stimulus frequency causes twitches to add, producing stronger contractions and tetanus.

  • Motor unit recruitment

    Increasing stimulus strength activates more motor units, increasing contraction force.

  • Isotonic vs isometric contractions

    Isotonic: muscle changes length; isometric: muscle tension increases without length change.

  • ATP sources for muscle contraction

    Direct phosphorylation by creatine phosphate, anaerobic glycolysis, and aerobic respiration.

  • Anaerobic glycolysis

    Glucose broken down to lactic acid without oxygen, producing 2 ATP quickly but inefficiently.

  • Aerobic respiration

    Oxygen-dependent process producing ~32 ATP per glucose, slower but efficient for prolonged activity.

  • Muscle fatigue causes

    Ionic imbalances, increased inorganic phosphate, decreased ATP, and glycogen depletion impair contraction.

  • Muscle fiber types

    Slow oxidative (endurance), fast oxidative (intermediate), and fast glycolytic (powerful, fatigable).

  • Smooth muscle differences from skeletal muscle

    Spindle-shaped, single nucleus, no striations, no troponin, uses calmodulin, slower contractions, involuntary.

  • Smooth muscle contraction regulation

    Controlled by neural, hormonal, and local chemical signals; Ca2+ activates myosin via calmodulin and myosin kinase.