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Muscle Tissue & Physiology - Anatomy & Physiology

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Terms in this set (25)

  • What are the three types of muscle tissue?
    Skeletal muscle (movement and posture), Cardiac muscle (heart pumping), and Smooth muscle (viscera movement and vasoconstriction).
  • What connective tissue layers surround skeletal muscle?
    Epimysium surrounds the whole muscle, Perimysium surrounds fascicles, and Endomysium surrounds individual muscle fibers.
  • What is a muscle fiber?
    A single muscle cell, long and cylindrical, multinucleated, also called a myocyte.
  • Describe the hierarchical structure of skeletal muscle from largest to smallest.
    Muscle → fascicles → muscle fibers → myofibrils → myofilaments.
  • What proteins make up the thick and thin filaments in muscle fibers?
    Thick filaments are made of myosin; thin filaments are made of actin, tropomyosin, and troponin.
  • What is a sarcomere?
    The functional unit of skeletal muscle, located between two Z-lines, containing thick and thin filaments.
  • What are the key regions of a sarcomere?
    Includes the A band, I band, H zone, M line, and Z line.
  • What is the role of myosin heads in muscle contraction?
    Myosin heads form cross-bridges by binding to actin and have ATPase activity to split ATP for contraction.
  • What proteins regulate the interaction between actin and myosin?
    Tropomyosin blocks active sites on actin; troponin binds calcium to move tropomyosin and expose binding sites.
  • What is the function of titin in the sarcomere?
    Titin stabilizes thick filaments and acts like a spring to return sarcomeres to resting length after contraction.
  • Explain the sliding filament theory.
    During contraction, thin filaments slide toward the sarcomere center, shortening the muscle fiber without changing A band width.
  • What occurs at the neuromuscular junction to initiate muscle contraction?
    Acetylcholine released from neuron binds receptors on motor end plate, opening sodium channels and triggering an action potential.
  • What is excitation-contraction coupling?
    Action potential triggers Ca2+ release from sarcoplasmic reticulum, Ca2+ binds troponin, moving tropomyosin to expose actin sites.
  • Describe the cross-bridge cycle in muscle contraction.
    Myosin head binds actin, pivots (power stroke), releases ADP + P, then ATP binds to release myosin and reset the head.
  • What happens during muscle relaxation?
    Ca2+ release stops, troponin and tropomyosin cover actin sites, preventing cross-bridge formation.
  • Define a motor unit.
    One motor neuron and all the muscle fibers it controls.
  • What is muscle tone?
    Continuous, low-level contraction of some motor units producing resting tension in skeletal muscles.
  • What are isotonic and isometric muscle contractions?
    Isotonic: muscle changes length with constant tension; Isometric: muscle length stays constant while tension develops.
  • What are concentric and eccentric contractions?
    Concentric: muscle shortens; Eccentric: muscle lengthens during contraction.
  • What energy sources support muscle contraction?
    ATP from stored reserves, creatine phosphate, anaerobic glycolysis, and aerobic respiration.
  • What causes muscle fatigue?
    Depletion of metabolic reserves, damage to muscle membranes, decreased pH, and impaired Ca2+ binding.
  • What are key structural differences of cardiac muscle cells?
    Smaller cells, single central nucleus, many mitochondria, intercalated discs with gap junctions, and no terminal cisternae.
  • How do cardiac muscle cells contract?
    They contract as a functional syncytium via gap junctions and have automaticity controlled by pacemaker cells.
  • What are characteristics of smooth muscle cells?
    Nonstriated, spindle-shaped, single nucleus, thin filaments attached to dense bodies, no T-tubules, involuntary control.
  • What is plasticity in smooth muscle?
    The ability to adjust tension over a wide range of lengths without changing contractile strength.