# neuroscience exam 2 lecture 2-12

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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-