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General and nerve – muscle physiology

  1. Cell Membrane: Thickness 7-10 nm MCQ, Fluid Mosaic Model MCQ, 30-40% lipid MCQ, 50-60% protein MCQ.
  2. Cell Junctions
    a. Tight junction: membranes fuse tightly, no transport possible
    b. Desmosmes MCQ : membranes are separated by 15-20 nm, but no transport of substances takes place
    c. Gap Junctions MCQ : 2-20 nm separation. Connexons seen. Contain ion channels, found in cardiac muscles
  3. Intercellular Communications: Neural – synapse, Paracrine MCQ – neighboring cells via ECF, Endocrine – via blood & Autocrine
  4. Body water and Body fluids: 60-70% is Total body water. Lower in females due to high fatty tissue MCQ. 1/3 is ECF MCQ and 2/3 is ICF MCQ
  5. Extracellular Fluid:  small in newborns MCQ (dehydration common).composed of Plasma (25% of ECF or 8% of body weight MCQ),  Interstitial fluid & Transcellular fluid (sweat, CSF, bile, gastric secretion etc)
  6. Measurement of body fluid compartments: by indicator dilution method
    a. TBW – Deuterium oxide MCQ, aminopyrene MCQ
    b. ECF Vol. – Inulin MCQ, Radioactive Cl-
    c. Plasma Vol. – Evans Blue Dye MCQ, Radio-iodinated human S. albumin or tagged RBCs method
    d. ICF Vol. – indirectly by TBW-ECF
  7. Glycolipids are widely distributed particularly in nervous tissue and brain. They occur particularly in outer plasma membrane where they contribute to cell surface carbohydrate. Addition of PUFA in plasma members causes increase in fluidity of membrane.
  8. Glycophorin present in RBC membrane help in ABO antigen binding.
  9. Equilibrium potential for anion is calculated by Nernst equation.
  10. Na+ - K+ pump is an active pump.
  11. Na+-K+ATP pump is an electrogenic pump that extrudes 3Na+ from the cell & take 2K+ into the cell. (coupling ratio is 3:2).
  12. Gibbs-Donnan Membrane Equlibrium MCQ: The conc. of various ionic solutes is different across the cell membrane i.e ICF & ECF. It is due to the presence of indiffusible ions. In cells indiffusible anion proteins & organic phosphate buffer are present as a result of which diffusible cation K+ is more inside whereas diffusible anion Cl- is more outside in ECF.
  13. Nernst Equation MCQ: because of asymmetrical distribution of ions across cell membrane there exists an electrical gradient whose magnitude(Equlilibrium potential MCQ) can be found by Nernst Equation.
  14. Resting Membrane Potential MCQ : it is the constant potential diff. across the cell membrane at rest. It is due to distribution of ions MCQ, ion pumps(Na+/K+ pump MCQ), membrane permeability MCQ.
  15.  Its value is – 70 mV in nervous tissue. (Equilibrium potential of Cl- is close to RMP i.e. -70 mV MCQ) Na+ has no effect on RMP.
  16. Action Potential: brief sequence of changes which occur in membrane potential following excitation
  17. Increased K+ in ECF causes depolarization.
  18. Increased permeability of Na+ causes depolarization and K+ cause hyperpolarisation.
  19. Resting membrane potential of a skeletal muscle is - 90mv
  20. Resting membrane potential of a smooth muscle is - 50 to 75mv
  21. Resting membrane potential of a cardial muscle is -85 to -95 mv
  22. IPSP is due to Cl- influx
  23. EPSP is due to Na+ /Ca2+ influx
  24. Lipids and proteins in cell membrane interactby hydrogen bonds
  25. Saturated fatty acids increase transition temperature and decrease fluidity
  26. Unsaturated fatty acids decrease transition temperature and increase fluidity
  27. Pinocytosis - engulfing liquid substances by enfolding of cell membrane.
  28. Emiocytosis - excretion of specific hormones and granules by cell in emiocytosis .requires calcium.
  29. Tanscytosis - vesicular transport with in cell (epithelial cells of intestine)
  30. Refractory Period MCQ – excitable cell if stimulated again may show decreased or no response to second stimulus. Absulute Refractory Period – no response to 2nd stimulus from firing level to 1/3 repolarisation.
  31. Relative Refractory Period MCQ – a stronger 2nd stimulus produces action potential, starts from end of ARP.
  32. Accommodation MCQ – if subthreshold stimulus is applied for a long time the membrane adapts and no AP is produced it is due to opening and delayed closing of K+
  33. Rheobase indicates magnitude of the current. Chronaxie is the time for double Rheobase current to cause stimulation of nerve /muscle, it is inversely proportional to excitability of tissue ( Less Chronaxie, more excitability)
  34. Action Potential: Develops in the initial segment of axon (Axon hillock) and the impulse is transmitted along the axon to its termination.
  35. Axon hillock is the initial segment of neuron, nerve impulses begin in this initial segment of axon because it has lowest threshold potential.
  36. Action potential is due to opening up Na+ channels causing Na+ influx. Action potential Follows ' All or None' phenomenon
  37. Conduction of nerve is an active self propagating process and impulse moves at a constant amplitude & velocity.
  38. Conduction is faster in Myelinated axons. A>B>C (C are unmyelinated)
  39. Axons can conduct nerve impulses in either direction unlike synapses, which permit conduction of nerve impulses in one direction only.
  40. Order of permeability in excitable tissue at rest K+> Cl->Na+
  41. Transmission at synapse is always in one direction only because the neurotransmitter substance responsible for conduction is present in vesicles of presynaptic neurons only. The post synaptic neuron contain the receptors
  42. Synaptic cleft is 20-40 mm wide.
  43. Picrotoxin inhibits presynaptic inhibition. Local anaesthetic do not affect presynaptic inhibition.
  44. Clathrin is used in receptor mediated endocytosis.
  45. D2O is used to measure vol. of total body water (TBW).
  46. Inulin & sucrose for ECF and Evan Blue dye for plasma.
  47. Ineffective osmols is Urea.
  48. Basement membrane degeneration is mediated by metalo-proteinases. Defect in collagen formation is seen in scurvy & osteogenesis imperfecta. Viscosity of synovial fluid is due to Hyaluronic acid.
  49. Products accumulated in Hunter's syndrome are dermatan sulfate & Heparan sulfate.
  50. Agranular cytoplasmicreticulum is involved in lipid synthesis.
  51. Granular cytoplamic reticulum is involved in protein synthesis.
  52. Glycolysis occurs in cytosol.
  53. Galactosyl transferase is a maker of golgi apparatus.
  54. Catabolism of H202 is carried out by peroxisomes.
  55. Cell shape and motility are provided by microfilaments.
  56. Sequence of cell cycle is G0-G1-S-G2.
  57. cAMP acts through activation of protein kinase. IP3/DAG via Ca2+
  58. Spectrin, ankyrin (pyramidal shaped) and other peripheral membrane protein eg actin, protein 4.1, tropomyosin maintain the shape & flexibility of RBC.
  59. Abnormalities in amount or structure of spectrin cause Hereditary Spherocytosis & Elliptocytosis.
  60. BMR depends on body surface area
  61. Hematocrit does not change in the old age
  62. In moderate exercise the respiratory rate increase due to response of propioception receptor in the joints.
  63. Histamine is formed by decarboxylation of amino acid histidine.
  64. In each sarcomere, I bands(made of actin) becomes narrower during muscle contraction. A band remain unchanged. H zone disappear.
  65. In resting skeletal muscle tropomyosin (a long filamentous protein, also called relaxation protein) covers the active sites of actin filament, where myosin head binds to action.
  66. Initiation of muscle contraction occurs, when Ca++ binds troponin C.
  67. Presence of intracellular Ca2+ is required for the contraction of all the three types of muscles - smooth, skeletal & cardiac. But in smooth calcium comes from ECF and in skeletal & cardiac from SR via ryanodine receptors.
  68. Calmodulin is involved in contraction of smooth muscle.
  69. In smooth muscle - phosphorylation of myosin is essential for contraction.In smooth muscles troponin is not required for contraction.
  70. In cardiac/skeletal muscle - Ca2+ ions initiate the process of contraction by binding with troponin C.
  71. Malignant Hyperthermia: This is life threatening event characterized by uncontrolled release of Ca+2 ions from the sarcoplasmic reticulum.

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