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Anatomy & Physiology: Muscular System

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Termini in questo insieme (20)

  • Types of muscle tissues
    Skeletal muscle: voluntary, striated, multinucleate; Cardiac muscle: involuntary, striated with intercalated discs, uninucleate; Smooth muscle: involuntary, non-striated, uninucleate, found in hollow organs.
  • Functions of skeletal muscle
    Skeletal muscles enable body movements, maintain posture, support soft tissues, guard entrances/exits, regulate body temperature, and store nutrient reserves.
  • Connective tissue coverings of skeletal muscle
    Epimysium: surrounds entire muscle; Perimysium: surrounds fascicles (bundles of fibers); Endomysium: surrounds individual muscle fibers.
  • Muscle fiber components
    Muscle fiber membrane is the sarcolemma, cytoplasm is sarcoplasm, and the specialized ER is the sarcoplasmic reticulum.
  • Myofibrils and myofilaments
    Myofibrils run the length of muscle fibers and contain myofilaments: thick myosin and thin actin filaments arranged in sarcomeres.
  • Sarcomere structure
    Sarcomeres are the basic contractile units, defined by Z lines, with A bands (thick filaments), I bands (thin filaments), and the M line in the center.
  • Origin vs. insertion of muscles
    Origin: less movable attachment; Insertion: more movable attachment. Muscle contraction pulls insertion toward origin.
  • Muscle naming criteria
    Muscles are named by location, shape, action, size, number of origins, origin/insertion sites, and fiber direction.
  • Muscle actions: flexion and extension
    Flexion: decreases angle between bones; Extension: increases angle between bones, e.g., straightening the arm at the elbow.
  • Sliding filament theory
    Muscle contraction occurs as actin and myosin filaments slide past each other, shortening the sarcomere without changing filament length.
  • Neuromuscular junction components
    Includes motor neuron axon terminal, synaptic vesicles with acetylcholine (Ach), synaptic cleft, motor end plate with Ach receptors, and sarcolemma.
  • Events at the neuromuscular junction
    AP arrives at axon terminal, triggers Ach release, Ach binds receptors on muscle fiber, ligand-gated channels open, causing muscle AP.
  • Role of calcium in muscle contraction
    Calcium released from sarcoplasmic reticulum binds to troponin, causing tropomyosin to move and expose actin binding sites for myosin.
  • Muscle contraction vs. relaxation
    Contraction is active, requires ATP and calcium; relaxation is passive, requires acetylcholinesterase to break down Ach.
  • Sources of ATP in muscle fibers
    Initial ATP from creatine phosphate; most ATP from aerobic respiration; anaerobic respiration used during oxygen debt but less efficient.
  • Types of muscle fibers
    Fast fibers: large, fatigue quickly, anaerobic metabolism; Slow fibers: small, fatigue resistant, aerobic metabolism.
  • Muscle tone and motor units
    Muscle tone is continuous resting tension; motor unit = motor neuron + muscle fibers it controls; summation and recruitment increase contraction strength.
  • Twitch vs. tetany
    A twitch is a single muscle contraction; tetany is sustained contraction from rapid repeated stimuli.
  • Muscle atrophy vs. hypertrophy
    Atrophy: loss of muscle size due to disuse; Hypertrophy: increase in muscle size from repeated exercise; fiber number remains constant.
  • Voltage-gated vs. ligand-gated ion channels
    Voltage-gated channels open in response to membrane potential changes; ligand-gated channels open when specific molecules bind, e.g., Ach at NMJ.