neuroscience exam 2 lecture 2-12

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neuroscience exam 2 lecture 2-12
2011-02-22 18:15:12


2 slide 12
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  1. membrance potential
    given as inside vs. outside. for example if the voltmeter indicates -65 that mean inside 65mv more negative than outside
  2. Membrance potential at rest
    At rest more negative ions on inside of membrance than rest
  3. Equilibrium potential for K is negative
    • 20 times more k+ inside (same as real nerve cell)
    • A-=anions (any negative ion) nothing happens w/o ion channels
  4. What happen K+ selective channels?
    Insert K+ selective channels in membrance diffusion pushes K+ outside, anions left behind -electrical force develops that pulls K+ ions back inside
  5. What happen at equilibrium?
    • Electrical force equals diffusion force, but oppostie direction. Equilibrium potential is voltage when electrical and diffusion forces balanced, no net K+ movement.
    • diffusion force=electrical force
  6. Equilibrium potential for Na is positive
    10 times more NA+ outside cell
  7. what happen with NA+ selective ion channels?
    If NA+ selective ion channels in membrance NA+ flows into cell b/c diffusion force
  8. what happen at NA+ equilibrium potential?
    Inside of cell becomes more and more positive until electrial force repels positive Na+ ions at equilibrium potential the diffusion forces pushing Na+ ion in is exactly counterbalanced by the electrial force pushing them out.
  9. Each ion has its own equilibrium potential
    • Ek+, Ena+,Eca2+, Ecl-
    • -equilibrium potential depends on concentration of that ion inside + outside cell
    • -can be calculated w/nernst equation
  10. Nernst equation
    • Eion=23 times RT/ZF times log [ion]outside/[ion]inside
    • R is gas constant
    • T absolute temp
    • Z charge of ion=+1 for k+/na+,+2 for ca2+,-1 for Cl-
    • F Faraday's constant
    • ion= outside concentration of ion outside cell
  11. Nernst Equation at bodytempeture
    Eion=61.5/z time log[ion]outside/[ion]inside
  12. The equilibrium potential is?
    Equilibrium potential is the membrane potential we measure when membrane is permeable to that ion alone. ex if only K+ ion channels in membrane, and 20times more K+ inside we get a membrance potential of -80mv. if only Na+ channels in membrane and 10 times more Na+ inside membrance potential is +61.5mv
  13. Resting membrance potential
    resting membrane potential of -65mv is close to ,but not at , equilibrium potential for K+, at rest membrane has mostly K+ channels open.