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Cell physiology2


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This presentation is about muscle fibers, muscle contraction, tetanus,
motor unit, summation.......

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Cell physiology2

  1. 1. Physiology of the cell by H. Khorrami Ph.D.
  2. 2. Muscle types • Cardiac Muscle – Striated muscle found only in the heart – Under involuntary control – Only rests between contractions • Smooth Muscle – Lack striations – Usually under involuntary control – Contraction is slow and rhythmic – Muscles of internal organs • Skeletal Muscle – Striated muscle fibers with no clear separation between cells – Under voluntary control
  3. 3. Muscles
  4. 4. • Synapse • Motor unit Neuro-muscular junction
  5. 5. Synaptic cleft
  6. 6. (Plasma membrane) Mammalian muscle Note alignment of T-tubules
  7. 7. Myofibril arrangement in muscle
  8. 8. • mk4 • F1D4
  9. 9. Titin • Largest protein with 34,350 AA • Mutation: – familial hypertrophic cardiomyopathy – Tibial muscular dystrophy
  10. 10. Synaptic transmission steps • Na-K conductance • Depolarization of presynaptic membrane • Motor end-plate potential • Increase Ca++ entrance • Ca2+-calmadulin • Synapsin-1 • Vesicle fusion • NT release
  11. 11. T-tubules are NOT positioned at M lines.
  12. 12. This gap is actually only ~10 nm. Ca2+ -ATPase
  13. 13. Molecular mechanisms of crossbridge action
  14. 14. This causes a conformational shift in the myosin head.
  15. 15. Actin filament components and Ca2+ activation F Troponin is a complex of three proteins including troponin C, a Ca2+ -binding protein closely related to calmodulin.
  16. 16. Binding of myosin to actin leads to release of Pi. After death, as ATP runs out, cytosolic [Ca2+ ] slowly rises, actin binding sites are opened, crossbridges are formed and become locked in the "rigor" position without ATP to bind.
  17. 17. Rigor Mortis
  18. 18. Single twitch
  19. 19. Summation of skeletal muscle tension; tetanus
  20. 20. Tetanus
  21. 21. Length-tension curve for skeletal muscle Full overlap between thick and thin filaments Decreasing overlap limits maximum tension No overlap (Muscles are not naturally stretched to this point) Actin poking through M line; myosin bumping into Z disk. Contraction range with normal skeletal movements
  22. 22. Lmax
  23. 23. Tension in muscle
  24. 24. Elastic elements • PEE • SEE • TEE
  25. 25. Contraction • Isometric • Isotonic – Concentric – Eccentric
  26. 26. Time is required for maximal twitch force to develop, because some shortening of sarcomeres must occur to stretch elastic elements of muscle before force can be transmitted through tendons By the time this maximal force is developed, [Ca2+ ] and number of active crossbridges have greatly decreased, so an individual twitch reaches much less than the maximum force the muscle can develop
  27. 27. Muscle Metabolism
  28. 28. Mitochondria generate ~32 ATP from one glucose (slow, but efficient). Glycolysis generates 2 ATP from one glucose (fast, but inefficient; lactate accumulates). Creatine kinase reaction: (fastest) ADP + creatine-P  ATP + creatine Adenylate kinase reaction (fast; used when ATP levels are very low): ADP + MgADP  AMP + MgATP
  29. 29. Muscle fiber types
  30. 30.  Central: involving central nervous system may involve such factors as dehydration, osmolarity, low blood sugar, and may precede physiological fatigue of actual muscles  Peripheral: in or near muscles, accumulation of lactate and pH, especially in fast-twitch fibers  inorganic phosphate may increasingly inhibit cleavage of ATP in the crossbridge cycle or in the sequestering of Ca2+ Muscle Fatigue
  31. 31. Muscle Spindle, Intrafusal Fibers • Motor • Sensory – Dynamic – Static
  32. 32. Nuclear Bag & Nuclear Chain
  33. 33. Muscle Control, Proprioception
  34. 34. Golgi tendon organ
  35. 35. Gamma Motoneuron
  36. 36. Motor unit • Small motor unit: 1-to-1 e.g. in EOM • Large motor unit: 1-to-2000 e.g. gastrocnemius muscle
  37. 37. Motor Unit: Fibers Innervated from 1 neuron • "All or none" within each motor unit • Fine touch – 1:1 nerve to fiber – Finger tips • Big muscles – 1: 2000 – Leg, postural muscles PLAY Animation: Muscular System: Contraction of Motor Units
  38. 38. Contractile force can also be regulated through activation of more, or fewer, motor units.
  39. 39. • Weak stimulus – Lowest threshold fibers – Slow twitch typically • Moderate: adds fast oxidative • High stimulus: all fibers • Asynchronous: – Units take turns – Prevents fatigue Recruitment of Fibers: Produce Graduated Force
  40. 40. Hypokalemia, Causes • Kidney disease • Diabetes • Cirrhosis(chronic alcoholism) • Laxative abuse(loose weight) • Diuretics • Steroids,… – steroid psychosis, mood changes, agitation, and irrational behavior • Corticosteroids( organ transplant, Cushing disease,…) • Hypervitaminosis B12
  41. 41. Hypokalemia, • Proximal muscle weakness • Myopathies • Cardiac arrhythmia • Hypokalemic periodic quadriparesis – Autosomal dominant disorder – Areflexic paresis – Irregular attacks – Large carbohydrate meals often precipitate attacks
  42. 42. Hyponatremia • Compulsive water intake • Adrenal insufficiency • Kidney disease • Hi ADH • Medications
  43. 43. Hyponatremia • Osmosis, cell swelling, cerebral edema,.. • Confusion, agitation, stupor • Nausea and vomiting • Headache, confusion • Loss of energy, drowsiness and fatigue • Restlessness and irritability • Muscle weakness, spasms or cramps • Seizures • Coma
  44. 44. Proprioceptors • Specialised sensory receptors within joints, muscles, and tendons • Sensitive to both tension and pressure • Play a role in relaying information concerning muscle dynamics to the conscious and subconscious parts of the CNS • They provide the brain with information concerning kinesthetic sense, or conscious appreciation of the position of body parts with respect to gravity • Mostly at subconscious level, • GTO located in tendons near the myotendinous junction and are in series
  45. 45. Techniques to Increase ROM • MET • PNF( Proprioceptive Neuromuscular Facilitation)
  46. 46. PNF Theories • Autogenic inhibition • Reciprocal inhibition • Stress relaxation • Gate control theory
  47. 47. PNF Techniques • Contract-Relax (CR) method • Contract-Relax-Antagonist-Contract (CRAC) Method • **PNF before exercise decrease the muscle performance • ** PNF after exercise increase the muscle performance
  48. 48. Ach Agonist • Stimulate Ach receptor but not destroyed by AchE: – Nicotine, carbacol & methacoline – Produce spasm
  49. 49. Skeletal Muscle Attachment • Tendon Attachments – Origin • Attachment to the bone that doesn’t move – Insertion • Attachment to the bone that does move • Antagonistic Pairs – Flexor • Flexes the joint (moves toward the body) – Extensor • Extends the joint (away from the body)
  50. 50. Rheobase & chronaxie
  51. 51. Trigger points • Is a hyperirritable spot, a palpable nodule in the taut bands of the skeletal muscles' fascia • Direct compression or muscle contraction can elicit jump sign, local tenderness, local twitch response and referred pain which usually responds with a pain pattern distant from the spot
  52. 52. Classification of Triger Point • Primary – Muscle belly, severe pain(jump sign) with pressure and radiate according to referred pain map • Secondary(satellite) or as cluster – Usually disappear when central trigger point heal • Active/Inactive(can increase stiffness) • Tendon, can develop degenerative process of the joint if not treated • Ligamentous, i.g. ant longitudinal, Ligamentum patellae, fibular collateral
  53. 53. Causes of Trigger Point • Injury sustained by a fall, by stress or birth trauma • Lack of exercise, commonly in sedentary persons, 45% are men • Aging • Bad posture, upper and lower crossed pattern, swayback posture, telephone posture, cross-legged sitting, • Muscle overuse and respective micro trauma, weightlifting, .. • Chronic stress condition, anxiety, depression, psychological stress trauma, • Vitamin deficiencies, vitamin C, D, B; folic acid; iron; • Sleep disturbance, • Joint problems and hypermobility
  54. 54. Pathophysiology • Overactive • Local inflammation • Loss of oxygen & nutrients • Involuntary muscle contraction • Higher demand to oxygen • Higher concentration of Ach, NAd, 5HT • Low PH
  55. 55. Muscle Cramp • If you’ve ever had a “charley horse” that odd pain in your calf, you’ve had a cramp • But they can happen anywhere in your body at any time, even when you’re asleep • No matter where you get them, what’s going on inside is the same: Your muscles suddenly tighten up when you don’t want them to • Several things can bring on cramps, but you can do some things to keep them from happening
  56. 56. Possible Cause: Not Enough Water • Cramps may be your body’s way of telling you that you need some, you’re dehydrated • Other signs include dizziness, headache, and constipation. So keep water with you and sip it throughout the day, especially if you’re outside in hot weather
  57. 57. High Temperatures • Your body loses fluids when you work or exercise in the heat, and that can make you more likely to cramp. This may be partly because your muscles need water, but it’s also because you sweat out important minerals called electrolytes, sodium, potassium, and calcium
  58. 58. Medications • Statins, which are used to control cholesterol, and diuretics, which help your body get rid of fluid, are just two of the drugs that can bring on cramping as a side effect
  59. 59. Poor Circulation • If your cramps get worse when you walk, your muscles may not be getting enough blood. That can happen as you get older or if you’re not very active. It also can be caused by a condition called claudication, when arteries are narrower than they should be and blood can’t get through easily
  60. 60. Monthly Cycle • Some women get cramps during their periods. That happens because a woman’s body makes certain hormones that make the muscles in her uterus tighten up. This helps push out blood and tissue, but it can also cause cramping
  61. 61. Growth • Kids often get cramps when they go through a growth spurt. These are sometimes called “growing pains,” but they may actually be caused by too much activity, or kids may just be more sensitive to pain. The cramps happen most often in the legs and can wake a child out of a sound sleep. It may help to stretch the muscle or put a heating pad on the area for a short time
  62. 62. Exercise • It’s important to stay active, but if you do too much all at once or your body’s not used to it, your muscles can cramp. Instead, pace yourself: Regular exercise can make your muscles stronger and harder to tire out, so they won’t cramp as easily. Be sure to warm up first, and do plenty of stretching before and after
  63. 63. How to Feel Better • Cramps usually go away on their own fairly quickly, but you can do some things to help them along. If an activity like running triggered one, stop right away. Then gently stretch or massage the muscle or use a heating pad or hot bath to bring blood to the area and relax it. Ice and over-the-counter anti-inflammatories, like ibuprofen, can help if you have pain and swelling, too
  64. 64. Why Stretching Helps • Muscles are bunches of fibers that quickly get smaller or bigger when you move your body to do something -- from grabbing something off a shelf to running a race. When you stretch those fibers regularly, they can do their job more easily, and that helps you cramp less
  65. 65. Why Your Diet Matters • Colorful fruits and vegetables have minerals called electrolytes that help keep your muscles in good shape and can help you avoid cramps. Leafy greens and bananas are good choices
  66. 66. Smooth muscle