Skeletal muscle

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Skeletal muscle
2013-02-26 13:25:03
Physiology t1

Physiology test 1, skeletal muscle
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  1. Smooth muscle
    • Internal organs, blood vessels, eye.  Produce movements in internal organs.  
    • involuntary, single nuclei, non-striated, spindle-shaped
    • nerve supply to visceral modifies, nerve supply to MULTIUNIT is necessary
  2. Cardiac muscle
    • Heart.  Pumps blood.  
    • Single nuclei, striated, branched, involuntary
    • nerve supply not necessary for function--modifies
  3. Skeletal muscle
    • skeletal muscles.  Moves bones, generates heat.  
    • Voluntary.  Multi-nuclei, striated, long, thin fibers. 
    • Nerve supply necessary for movement
  4. epimysium
    connective tissue that encircles all fascicles to form a complete muscle
  5. perimysium
    connective tissue that encircles a group of muscle fibers forming a fascicle
  6. Fascicle
    a group of muscle fibers (held together by a perimysium)
  7. Endomysium
    connective tissue that surrounds each muscle fiber or cell.  
  8. Tendon
    where epimysium, perimysium and endomysium come together to attach to a bone
  9. Sarcoplasm
    muscle cytoplasm
  10. sarcoplasmic reticulum
    • muscle endoplasmic reticulum
    • surrounds each myofibril.  Inside, lots of CALCIUM
  11. Sarcolemma
    plasma membrane of a muscle cell
  12. T(ransverse)-tubules
    • invaginations of the sarcolemma into the inside of the muscle at a right angle.  
    • Action potential travels inside of them to stimulate SR and release calcium for contraction
  13. Actin
    • thin filament in muscles.  In I-band (across Z-line) in a sarcomere.  Double helix made of F-actin (string) and G-actin molecules (pearls).  
    • Tropomyosin and troponin attached.  Moved by myosin
  14. Myosin
    • thick filament.  Tail, hinge and head.  Head has ATP/ADP and phosphate to help move actin filament.  
    • Makes up H-zone in sarcomere.
    • All heads in the same direction (on each side).  Tails point towards the H-zone
  15. Organization of skeletal muscles
    • Muscle bundle
    • muscle fiber
    • myofibril
    • sarcomere
    • (myofilaments) actin and myosin filaments
  16. Z-line
    boundaries of a single sarcomere.  Includes actin and myosin filaments (half I-band, A-band, H-zone)
  17. A-band
    section of a sarcomere containing myosin.  Some actin is inside too
  18. I-band
    section in sarcomere that contains only actin, spans the Z-line so half is in each sarcomere.  Disappears as muscle contracts
  19. H-zone
    portion of sarcomere that contains only myosin, in the middle.  Disappears as muscle contracts.  
  20. F actin
    string part of double helix that makes up actin filament
  21. G-actin
    pearls of actin filament
  22. Triad
    A T-tubule and two terminal cisternaes (part of sarcoplasmic reticulum)
  23. Dihydropyradine receptor
    DHP, on T-tubule.  Receptor that depolarizes to signal the Ryanodine (RyR) receptor and allow calcium out of the sarcoplasmic reticulum
  24. Ryanodine receptor
    on sarcoplasmic reticulum, receptor that opens when DHP is depolarized to release calcium into the cell and cause muscle contraction
  25. Tropomyosin
    evil stepmother that covers myosin binding sites on the actin filament until distracted by a calcium-troponin bond.
  26. Troponin
    Tiny bubbles on tropomyosin with three sub-units (bond to G-actin, Calcium or Tropomyosin)
  27. Power stroke
    when myosin filaments move actin filaments toward the H-zone, contracting the muscle.  
  28. Actin and myosin contraction
    action potential goes through DHP, RyR releases calcium, calcium binds to Troponin, Troponin-Ca moves Tropomyosin, Myosin binds to Actin, Myosin hinges move actin towards the H-zone (due to release of ADP and P), causing the power-stroke that contracts the muscle, ATP phosphorylates, re-cocking the hinge
  29. Termination of muscle contraction
    energy (ATP) is required to pump Ca2+ back into sarcoplasmic reticulum.  Everything releases back into its original form. 
  30. Action potential from cardiac muscle is different because:
    it contains a plateau instead of a spike, caused by opening of voltage-gated calcium channels (slower).  Slower depolarization, extends before repolarization.  Longer absolute refractory period creates a forced pause between beats for the ventricles to fill (no tetany)
  31. Strength of muscle tension is dependant on
    length of sarcomere pre-contraction.  Maximum number of cross bridges is ideal--should be overlap but still contain an h-zone and I-zones. 
  32. Twitch (3, last one has 3)
    • single instant reaction of muscle, 20-200 milliseconds, goes through phases one time. 
    • Neuro action potential (spike)
    • Muscle action potential (wider, a little less spike)
    • Muscle contraction (Latent, contraction, relaxation)
  33. phases of muscle contraction
    • latent (action potential to calcium release)
    • contraction (calcium release to power stroke)
    • Relaxation (calcium pumped back into SR, ADP/ATP released to recock myosin head)
  34. Treppe
    A gain of muscle twitch (more forceful but not longer) caused by a second stimulation shortly AFTER the relaxation phase of the first twitch.  Not all calcium was pumped back into SR so there is more force/tension. 
  35. wave summation
    • gain of muscle reaction (stronger AND longer) caused by second stimulation DURING relaxation phase.  Makes for a graded or sustained contraction, smoother response. 
    • Can result in FUSED tetanus, for smooth contraction
  36. Fused tetanus
    during wave summation when so many impulses are coming so fast that reactions become constant and smooth.  A contraction.   Graded, smooth, continuous. 
  37. Tetanus
    stimuli coming quickly, twitch goes through fused summation for a prolonged contraction.  (Normal)
  38. Spatial Summation
    • Greater force of muscle contraction by INCREASING the number of motor units that fire at one time.  (more motor units will cause a contraction to get stronger/longer)
    • AKA multiple motor unit summation or recruitment summation
  39. Multiple motor unit summation
    Greater force of muscle contraction by INCREASING the number of motor units that fire at one time.  (more motor units will cause a contraction to get stronger/longer)AKA spatial summation or recruitment summation
  40. recruitment summation
    Greater force of muscle contraction by INCREASING the number of motor units that fire at one time.  (more motor units will cause a contraction to get stronger/longer)AKA multiple motor unit summation or spatial summation
  41. Delicacy of muscle motion
    • is dependant on number of fibers controlled by a single motor unit--less is more.
    • Smaller motor muscle unit=more delicate movement
    • larger muscle motor unit=less precise movement
  42. phosphocreatine
    • storage for ATP in muscle.  Short-term, so more needs to be made constantly.  Stored during rest. 
    • phosphocreatine + ADP --(creatine kinase)--> creatine + ATP
  43. Ways for muscle to get ATP
    • creatine-phosphate (into creatine, into ATP)
    • Anaerobic (glycogen by glycolosis into lactic acid into ATP)
    • Aerobic (Most, cellular respiration, electron transport chain)
  44. How can you interefere with muscle synapse?
    • Block release of ACH
    • too much ACH
    • No breakdown of ACH
  45. What was wrong with Maggie?  Wound, flaccid paralysis, weak tongue, eyelid tone, difficulty chewing and swallowing. 
    Botulism.  Food poisoning, wound poisoning in horses.  Toxin interrupts nerve transmission--prevents release of ACH.  Acute symptoms.  treated with antitoxin and antibiotics. 
  46. What was wrong with Fifi?  Fatigue and exercise-induced weakness, change in voice, vomiting.
    Myasthenia Gravis.  antibodies attacking nicotinic receptors, blocking action potential.  Can cause megaesophagus.  Often in dogs, rarely in cats.  Give tensulin--quick easy test that exposes nicotinic sites and temporarily cures symptoms