1. Epimysium
    Fibrous connective tissue covering the skeletal muscles; continuous with tendons at the ends of the muscle.
  2. Bone Periosteum
    A specialized connective tissue covering all bones; tendon is attached here.
  3. Muscle Fibers
    AKA muscle cells; long, cylindrical cells 50-100micrometer diameter; contain several nuclei
  4. Fasiculi
    Bundles of up to 150 muscle fibers; found under the epimysium
  5. Perimysium
    Connective tissue surrounding the fasiculi.
  6. Endomysium
    Connective tissue surrounding each muscle fiber; is continuous with the sarcolemma
  7. Sarcolemma
    Muscle fiber's membrane
  8. Motor Neuron
    Nerve cell
  9. Neuromuscular Junction
    The junction between a motor neuron and the muscle fibers it innervates; AKA motor end plate
  10. Motor Unit
    A motor neuron and the muscle fibers it innervates
  11. Sarcoplasm
    The cytoplasm of the muscle fiber; contains contractile components
  12. Myofibrils
    Contain the apparatus that contracts the muscle cell; hunderds of myofibrils dominate the sarcoplasm
  13. Myosin Filament
    Thick filament about 16 nm in diameter that contain up to 200 myosin molecules
  14. Cross-bridges
    Globular heads protruding away from the myosin filament at regular intervals
  15. Actin Filaments
    Thin filaments about 6nm in diameter; consist of 2 strands arranged in a double helix
  16. Sarcomere
    Smallest contractile unit of skeletal muscle; average about 2.2 micrometers in length in a relaxed fiber and are repeated the entire length of the muscle fiber.
  17. A-band
    Dark; corresponds with the alignment of the myosin filaments
  18. I-band
    Light, corresponds with the areas in two adjacent sarcomeres that contain only actin filaments
  19. Z-line
    The middle line of the I-band and appears as a thin, dark line running longitudinally through the I-band
  20. H-zone
    The area in the center of the sarcomere where only myosin filaments are present
  21. Sarcoplasmic Reticulum
    Intricate system of tubules parallel to and surrounding each myofibril that terminates as vesicles in the vicinity of the Z-lines; store calcium ions
  22. T-tubules
    Run perpendicular to the sarcoplasmic reticulum and terminate in the vicinity of the Z-line between two vessicles; AKA transverse tubules
  23. Triad
    Pattern of a T-tubule spaced between and perpendicular to two sarcoplasmic reticulum vessicles
  24. Action Potential
    An electrical nerve impulse
  25. Sliding Filament Theory
    Actin filaments at each end of the sarcomere slide inward on myosin filaments, pulling the Z-lines toward the center of the sarcomere and thus shortening the muscle fiber.
  26. Troponin
    A protein that is situated at reular intervals alond the actin filament and has a high affinity for calcium ions; calcium ions released from the sarcoplasmic reticulum bind with troponin
  27. Tropomyosin
    Protein molecule that runs along the length of the actin filament in the groove of the double helix
  28. Resting Phase of Sliding-Filament Theroy of Muscular Contration
    Little calcium is present in the myofibril, so very few of the myosin cross-bridges are bound to actin; no tension is developed in the muscle
  29. Excitation-Contraction Coupling Phase of Sliding-Filament Theroy of Muscular Contration
    Sarcoplasmic reticulum is stimulated to release calcium ions, which bind with troponin, causing a shift in the tropomyosin. Mysoin cross-bridge head now attaches more reapidly to actin filament
  30. Contraction Phase of Sliding-Filament Theroy of Muscular Contration
    The energy for cross-bridge flexion comes from hydrolysis of ATP to ADP and phosphate, which is catalyzed by ATPase. Another ATP molecule must replace ADP on the myosin cross-bridge head in order for the head to detach from the active actin site and recock.
  31. Recharge Phase of Sliding-Filament Theroy of Muscular Contration
    Measurable muscle shortening transpires only when the binding of calcium to troponin, coupling of the mysoin cross-bridge with actin, cross-bridge fexion, dissociation of actin and myosin, and recocking of the mysosin cross-bridge head is repeated over and over throughout the muscle fiber.
  32. Relaxation Phase of Sliding-Filament Theroy of Muscular Contration
    Occurs when the stimulation of the motor neuron stops. Calcium is pumped back into the sarcoplasmic reticulum, which prevents the link between the actin and myosin filaments. Brought on by the return of actin and myosin filaments to their unbound states
  33. Acetylcholine
    Neurotransmitter released by the arrival of the action potential at the nerve terminal, which diffuses across the neuromuscular junction, causing excitation of the sarcolemma
  34. All-or-None Principle of Muscle
    There is no such thing as a motor neuron stimulus that causes onle some of the fibers to contract. Similarly, a stronger action potential cannot produce a stronger contraction.
  35. Twitch
    The brief contraction that results from an action potential traveling down a motor neuron, activating the muscle fibers
  36. Tetanus
    When stimuli are delivered at so high a frequency that the twitches begin to merge and eventually completely fuse
  37. Fast-twitch Motor Unit
    One that develops force and also relaxes rapidly and thus has a short twitch time.
  38. Slow-twitch Motor Unit
    One that develops force and relaxes slowly and has a long twitch time
  39. Type I fibers
    Slow-twitch; generally fatigue resistant and have a high capacity for aerobic energy supply, but limited potential for raped force development
  40. Type II Motor Units
    Fast-twitch; characterized as inefficient and fatigable and having low aerobic power, rapid force development, high actomyosin myofibrillar ATPase activity, and high anaerobic power.
  41. Recruitment
    Means of vaying skeletal muscle force involving an increase in force through varying the number of motor units activated.
Card Set
Structure and Function of the Muscular, Neuromuscular, Cardiovascular, and Respiratory Systems