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2012-06-19 16:15:07

Ch.9 - Muscle and Muscle Tissue - Lecture Test #4
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  1. Sarcolemma
    Muscle plasma membrane
  2. Functional Characteristics of Muscle Tissue
    • 1. Excitability
    • 2. Contractility
    • 3. Extensibility
    • 4. Elasticity 
  3. Skeletal Muscle Function
    • 1. Movement
    • 2. Posture
    • 3. Stabilize Joints
    • 4. Generate Heat 
  4. Endomysium
    Surrounding each individual muscle fiber.

    Fine sheath of CTT composed of reticular fibers & loose CT.
  5. Perimysium
    Surrounds groups of muscle fibers (fasicles)

    Fibruous CT 
  6. Epimysium
    Surrounds the entire muscle

    dense irregular CT (mostly collagen bundles)
  7. Deep Fascia
    Each Skeletal muscle is covered with this tough fibrous layer of CT. May extend past the length of the muscle and attach that muscle to a bone.
  8. Muscle Attachment: Origin
    Less moveable site on bone at which tendons attach

    helps to stabilize the muscle 
  9. Muscle Attachment: Insertion
    site on bone which tendons attach to allow muscle contraction and to move bone around a joint
  10. Tendon
    • - tough collagen fibers
    • - found at end of muscle
    • - epimysium comes together to form a tendon
    • - CT of muscle wrappings continuous with tendons
    • - no muscle fibers 
  11. Satellite Cells
    myoblasts that do not fuse, but can aid in repair and some regeneration in adults.

    Satellite cells can divide and fuse to fibers for repair but cannot generate new fibers 
  12. Sarcoplasm
    Cytoplasm of muscle cells
  13. Gylcosomes
    granules that store glycogen (which can be converted to glucose and then ATP)

    contained in the sarcoplasm 
  14. myoglobin
    oxygen binding protein

    red pigment (stores Oxygen) 
  15. Sarcoplasmic Reticulum
    Smooth ER of muscle cell

    surrounds each myofibril 
  16. Sarcolemma
    Plasma member of muscle fiber

    forms a membrane connection between each sarcomere by means of T tubules 
  17. T-tubules
    membranous channels that extend into the sarcoplasm as invaginations continuous with muscle cell sarcolemma

    filled with extracellular fluid from cell's exterior

    penetrate into cell's interior at A band - I band junction
  18. Triad
    T-tubule with Sarcoplasmic Reticulum on each side

    Contains integral membrane proteins act as voltage sensors

    Foot proteins are gated channels that regulate Ca release from Sarcoplasmic Reticulum
  19. Sarcomere
    Smallest contractile unit of a muscle

    Region between two succesize Z-discs.

    • Ca ions are pumped into the sarcomere from the SR terminal cisternae to begin muscle contraction.
  20. Actin
    Thin Filament
  21. Myosin
    • Thick Filament
    • Has Heads and Tails 
  22. A Band
    • Dark Band
    • Actin and Myosin fibers overlapping
  23. I Band
    • Light band
    • actin filaments only 
  24. Z-disc
    • Darker midline in the I-band
    • Formed by coin shaped sheet of proteins of a-actinin 
    • helps keep the actin fibers in place
  25. Titin
    elastic filaments that attach thing & thick filments to the Z-disc
  26. H-zone
    • lighter region in the middle of A band
    • Thing filaments do not overlap thick filaments
    • No myosin heads, only tails 
  27. M-line
    • darker region in middle of H-zone
    • Composed of myomesin - helps hold adjacent filmanents together 
  28. Myosin Heads
    • Two sites:
    • a. Actin binding site
    • b. ATP binding site 
  29. Tropomyosin
    • Thread like strands of protein that spiral around the actin
    • covers actin binding site when muscle is at rest
    • blocks myosin cross bridge from binding to actin molecule.
  30. Troponin
    • Polypeptide complex located on tropomyosin
    • Binds Ca
    • Inhibits myosin binding by binding to actin
  31. Sliding Filament Model of Contraction
    • Thin filaments slide past the thick filaments
    • in relaxed state thin and thick overlap only slightly 
  32. Motor Neurons
    Stimulate skeletal muscle
  33. Neuromuscular Junction
    Where motor neuron meets muscle fiber. 
  34. Motor End Plate
    Part of the sarcolemma that is highly folded and contains acetylcholine (ACh) receptors and helps form the neuromuscular junction
  35. Synaptic Vesicles
    small membrane sacs filled with the neurotransmitter Acetylcholine (ACh) within the axon terminals of the motor neuron.
  36. Synaptic Cleft
    tiny space that separates the axon terminal ends and muscle fibers.

    Filled with a gel like extracellular fluid composed of collagen fibers and glycoproteins
  37. Events at Neuromuscular Junction
    • 1. Voltage-regulated Ca channels open allow Ca to enter the axon terminal
    • 2. Ca inside the axon terminal causes synaptic vesicles to fuse the axon terminal plasma membrane
    • 3. Fusion relases ACh into synaptic cleft via exocytosis
    • 4. ACh diffuses across the synaptic cleft to ACh receptors on the sarcolemma (motor end plate)
    • 5. Binding of ACh to its receptors initiates an ACTION POTENTIAL in the muscle
    • 6. ACh is destroyed by Acetylcholinesterase
  38. End Plate Potential
    • A local electrical event
    • Interior of sarcolemma becomes less negative
    • More Na diffuses in than K out.
    • Depolarization
  39. Action Potential
    A transient depolarization event that includes polarity reversal of a sarcolemma and the propagation of an action potential along the entire membrane.
  40. Generation of an Action Potential
    • End plate potentials spreads to adjancent sarcolemma
    • Causes voltage gated Na channels to open
    • Na leaves the cell which causes a decrease in membrane voltage
    • Once critical threshold is reached an action potential is generated 
  41. Propagation of an Action Potential
    • Local depolarization wave contenues to spreads changing the permeability of the sarcolemma
    • More voltage gated Na channels open in the adjacent patch causing it to depolarize
    • Once initiated the action potential is unstoppable and results in muscle contraction 
  42. Repolarization
    • Occurs immediately after depolarization wave passes
    • Na+ channels close
    • Voltage gated  K+ channels open
    • K+ diffuses out of the cell restoring the resting polarity
    • must occur before muscle can be stimulated again (refractory period
  43. Excitation Contraction Coupling (E-C coupling)
    Sequence of events by which an action potential occurs and depolarizes the sarcolemma which leads to the sliding of actin and myosin myofilaments

    Between Action Potential and muscle shortening 
  44. Excitation Coupling Steps
    • ACh is released from axon terminal of motor neuron
    • ACh diffuses across synaptic cleft
    • ACh binds onto receptor sites on sarcolemma
    • Na+ ions initiate and generate an Action Potential
    • Action Potential is propogated along the sarcolemma
    • Action Potential travels down the T-tubules
    • Voltage sensitive t-tubule proteins change shape and cause SR foot proteins to change shape as well
    • SR releases Ca+ ions in massive amounts
    • Ca+ ions diffuse into sarcomeres and bind to troponin
    • Troponin changes shape and removes blocking action of tropomyosin exposing the actin binding site
    • myosin binds to actin (cross bridge forms) 
  45. Disconnecting of Actin and Myosin
    ATP binds to myosin to release, cock, and reposition the myosin head on the actin
  46. Rigor Mortis
    • Following death...
    • Ca leaks out of SR causes muscles to contract
    • Ca binds to troponin, tropomyosin frees actin, cross bridge forms but cannot detach because no ATP
    • Peak rigidity at 12 hours
    • Dissipates over next 48-60 hours as proteins breakdown 
  47. Muscle Tension
    The force exerted by a contracting muscle on an object
  48. Motor Unit
    Nerve and all the muscle cells it makes a neuromuscular junction with

    Avg # of muscle fibers per motor unit is 150 muscle cells/neuron 
  49. Large Motor Units
    • Coarse movements
    • found in large weight-bearing muscles (thighs, hips) 
  50. Small Motor Units
    • Fine movements
    • example: fingers  
  51. Muscle twitch
    Response of a muscle to a single, brief threshold stimulus (AP) on it's motor neuron
  52. 3 Phases of Muscle Twitch
    • 1. Latent Period
    • - Tension begins, no change in length

    • 2. Period of Contraction
    • - Tension increases and peaks, muscle shortens

    • 3. Period of Relaxation
    • - muscle relaxes, tension decreases, Ca reabsorbed
  53. Graded Muscle Response
    It is the variation of stimulation needed in skeletal muscle contraction in order to have controlled movement.

    • Muscle can be graded in 2 ways
    • 1) changing frequency of stimulation
    • 2) changing strength of stimulation 
  54. Temporal/Wave summation 
    • Muscle contractions are summed
    • muscle is already partially contracted when 2nd stimulus is delivered and ever more Ca is released into the cytoplasm from SR
    • Muscle does not have time to completely relax
    • Increases contractile force 
  55. myogram
    graphic recording of contractile activity
  56. Incomplete Tetanus
    the muscle relaxes slightly before the next contraction
  57. Complete Tetanus
    the muscle does not relax at all betweeen stimuli

    maximal tension is reached 
  58. Muscle Fatigue
    muscle is unable to contract and its tension drops to zero

    due to inability to produce enough ATP 
  59. Treppe
    • Steplike increase in tension after repeated stimulation of a muscle even though muscle is allowed to complete each relaxation phase
    • muscle enyzmes become more efficient because heat is increased as muscle contracts 
    • Contractions increase because there is increased availability of Ca. 
  60. 4 phases of temporal summation
    • 1. Treppe - tension due to warming and increased enyzme efficiency
    • 2. Incomplete Tetanus - Rapid cycles but some relaxation
    • 3. Complete Tetanus - Smooth sustained contraction
    • 4. Fatigue - tension decreases due to low ATP and buildup of lactic acid
  61. Multiple Motor Unit Summation / Recruitment
    • caused by increasing strength of stimulus
    • more motor units contracting simultaneously
    • smallest muscle fibers activated first followed larger fibers 
  62. Muscle tone
    • State of partial contraction even when at rest which does not produce active movements
    • helps stabilize joints and maintain posture 
  63. Isometric contraction
    • results in increases in muscle tension but no lengthening or shortening of the muscle occurs
    • example: standing 
  64. Isotonic Contractions
    • Results in movement occuring at the joint
    • example: walking
  65. Eccentric Contraction
    Type of Isotonic contraction in which Lengthening of the muscle occurs
  66. Concentric Contraction
    Type of isotonic contraction in which Shortening of the muscle occurs
  67. 3 Pathways for generating ATP
    • 1. From energy of creatine phosphate (15 seconds worth)
    • 2. From anaerobic glycolysis ( 30-40 sec. worth)
    • 3. From aerobic cellular respiration
  68. Anaerobic Threshold
    Point where muscle start to use the anaerobic glycolysis pathway
  69. Aerobic endurance
    length of time a muscle can continue to contract using aerobic pathway
  70. Oxygen Debt
    Extra oxygen needed for a muscle to return to a resting state
  71. Slow Oxidative Fibers
    • contract slowly
    • fatigue resistant 
  72. Fast Oxidative
    • Contract quickly
    • moderate resistance to fatigue
    • Not found in humans 
  73. Fast Glycolytic Fibers
    • Contract quickly
    • easily fatigued 
  74. Hypertrophy
    • Muscles get larger
    • from resistance training
    • increased mitochondria, increased myofilaments
    • increase in glycogen stored in muscle 
  75. Aerobic Exercises
    • increase in slow oxidative fibers
    • increase in capillary penetration, number of mitochondria, and increased synthesis of myoglobin 
  76. Calmodulin
    Takes place place of troponin in Smooth muscle
  77. Stress-Relaxation Response
    • Smooth muscle responds to a stretch only briefly and then adapts to new length
    • retains its ability to contract
    • Allows stomach, bladder, etc, to temporarily store contents
  78. Single Unit vs. Multi-unit  Smooth muscle
    • Single unit
    • contract rhythmically as a unit
    • electrically coupled to one another via gap junctions
    • Multi-unit 
    • gap junctions are rare
  79. Regeneration by Muscle type:
    • Skeletal - can not divide
    • Cardiac - can not divide
    • Smooth - can divide and regenerate
  80. Peristalsis
    • Alternating contractions and relaxations of smooth muscles that maix and squeeze substances through the lumen of hollow organs
    • When the longitudinal layer contracts -> organ dilates and contracts
    • When the circular layer contractions -> orgran constricts and elongates