2.9

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efrain12
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241006
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2.9
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2013-10-16 13:25:15
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membrane potential and excitation
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  1. physics)principle #1) what is potential energy?
    • separation of positive and negative charges
    • *results in voltage
  2. physics)principle #1) what is kinetic energy?
    • allows the separated charges to move freely
    • *flow is called Amps
  3. physics)principle #1) What is resistance?
    the force which slows down current flow
  4. physics)principle #1) what is an insulator?
    substance which inhibits current flow
  5. physics)principle #1) what is conductor?
    promotes current flow
  6. physics)principle #1) what is the formula of Ohm's law?
    Current= Voltage/resistance
  7. Physics applied to living systems) what is the current?
    • ion flow
    • *NA, K
  8. Physics applied to living systems) example of potential enrgy creation?
    charge separation
  9. Physics applied to living systems) example of insulator?
    plasma membrane
  10. Physics applied to living systems) example of conductors
    • channels
    • *integral transmembrane proteins
  11. channels) What are passive channels?
    • they are always open and allow specific ions to flow through them
    • *leaking
  12. channels) what are active gated channels?
    only open when stimulated
  13. channels) 2 types of active gate channels?
    chemical and voltage
  14. channels)(active) how do chemical gated channels open?
    • by chemical stimulus
    • *ligand binds to the receptor then it opnes
  15. channels)(active) How do voltage gated channels open?
    by change in potential energy
  16. which 2 factors does current flow depend on?
    -electrical charge movement

    -chemical diffusion
  17. factors that current flow depend on- what is electrical charge movement
    ions that are charged will move toward an area that contains an opposite charge
  18. factors that current flow depend on- chemical diffusion
    diffuse from an area of high concentration to low concentration
  19. what 2 forces are known are electrochemical gradient?
    -chemical diffusion

    -electrical charge movement
  20. resting membrane potential) definition
    created by unequal concentrations of ions of both charges that exist in a narrow band around each side (cytoplasmic and extracellular) of the plasma membrane
  21. what is referred to as charge separation?
    • polarization of the membrane
    • *basis of all electrical conductivity of cells
  22. Is the cell electrically neutral?
    yes
  23. generation and maintenance of RMP) polarization
    • specific ions separate themselves at different concentrations immediately around the membrane
    • *CL, K, NA are allowed to move in back and forth
    • *A isnt
  24. generation and maintenance of RMP)  what 2 things generate the concentration difference?
    -NA/K ATPase pump

    -passive K and NA channesl
  25. generation and maintenance of RMP)  what is the NA/K ATPase pump method?
    • it pumps 3 NA out and 2 K are pumped into the cell simultaneously.
    • *antiport example
  26. generation and maintenance of RMP)  what 3 things does the NA/K ATPase pump do?
    -pumping creates equilibrium from being reaches

    • -maintain unequal distirbution of ions
    • *because more positives are coming out then bringing in, this creates a negative environment inside

    -electro-chemical gradient
  27. generation and maintenance of RMP) what do the passive channels of K and NA allow?
    allows K to move out and NA to move in
  28. generation and maintenance of RMP) why does K move out?
    K is already pumped in by the NA/K pump therefore it wants to move along the concentration gradient
  29. generation and maintenance of RMP) passive channels- which ion has more channels? K or NA?
    K
  30. which 2 cell types change their membrane potential?
    nerve and muscle
  31. Can other cells other than muscle of nerve alter their membrane potential?
    no, they maintain a constant resting memebrane potential throughout life
  32. what is a polarized cell
    • is a cell with a charge that is separated across
    • *-70MV
    • **resting potential cell
  33. what is a depolarized cell? (3)
    -not polarized

    -charges have been allowed to flow

    -potential enrgy is 0 MV
  34. what is hyperpolarized cell?
    • more polarized than the resting potential
    • *potential energy is greater
  35. what is repolarized?
    return polarity to baseline

    **return from hyperpolarized state> decrease potential energy, return from depolarized state> increase potential energy
  36. what are the 2 mechanisms that change the plasma membrane potential?
    -graded potential

    -action potential
  37. how do graded potential and action potential differ?
    in amount of ions that move and type of membrane channel which opens
  38. characteristics of chemically gated (2)
    • -few ions cross the membrane
    • *more than resting potential though

    • -small and limited graded potential
    • *small spark and it is limited
  39. characteristics of voltage gated  (2)
    -many ions cross the membrane

    • -large and all or none
    • *large spark and if it sparks it goes throughout the membrane.
  40. graded potentials) what channels do cells capable of conducting graded potentials have?
    chemically gated channels
  41. graded potentials) what happens when the gates are opened? (3)
    -few ions go across

    -often only one type of ion

    -area of membrane that changes potential is relatively small
  42. graded potentials) what 2 states can graded potentials create?
    depolarized and hyperpolarized
  43. graded potentials) when positive charges neutralize negative interior, what occurs?
    depolarization
  44. graded potentials) when positive charges leave interior of the cell, what occurs?
    hyperpolarization
  45. action potentials) what type of channels do cells contain the ones that are capable of creating action potentials?
    voltage-gated channels
  46. action potentials) are the voltage channels specific for an ion or broad?
    specific
  47. how are action potentials usually initiated by?
    graded potentials at a different area of the membrane
  48. 4 phases of AP) Resting phase
    -closed gated channels

    • -Resting membrane potential exists
    • * there are ion movements but not on these chemical or voltage channels
  49. 4 phases of AP) Action phase:Depolarization (3)
    -hemically gated channels open

    -NA enters which depolarizes membrane which

    -causes NA voltage gated channels to open
  50. 4 phases of AP) active phase: repolarization
    -NA channels close

    -chemically gated channels have already closed

    • -K voltage channels open
    • *these will not open unless it senese a large positive gradint on the interior side of membrane
    • *K will leave the cell along the electrochemical gradient
  51. 4 phases of AP) Active phase: Hyperpolarization
    • -K channels stay open awhile
    • *goes into negative bc the K channels allow K to keep moving out
  52. what restores the membrane to be ready for the next Action potential?
    NA/K ATPase pump
  53. where do Action potential travel along the membrane?
    where there are voltage gated channels
  54. whats action potential threshold?
    • must have enough stimulus to open the voltage gated channels
    • *sometimes the graded potential did not reach the threshold to create AP
    • **occurs frequently
  55. Once voltage gated channels open...
    AP goes through the length of membrane, no exceptions
  56. what are refractory periods?
    • period where all ions need to be returned to baseline lcoations
    • *sodium out and K in
    • **NA/K pump does this
  57. 2 types of refractory periods
    -absolute

    -relative
  58. refractory periods) Absolute (2)
    -incapable of stimulus response, an AP

    • -happens immediately after
    • *ions are on the wrong side of baseline locations
  59. refractory periods) Relative (2)
    -large stimulus can generate an action potential

    -na/k pump has had chance to sort of sort through all the ions but only a big spark can create an AP

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