# neuroscience exam 2 lecture 2-12

 membrance potential given as inside vs. outside. for example if the voltmeter indicates -65 that mean inside 65mv more negative than outside Membrance potential at rest At rest more negative ions on inside of membrance than rest 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 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 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 Equilibrium potential for Na is positive 10 times more NA+ outside cell what happen with NA+ selective ion channels? If NA+ selective ion channels in membrance NA+ flows into cell b/c diffusion force 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. 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 Nernst equation Eion=23 times RT/ZF times log [ion]outside/[ion]insideR is gas constantT absolute tempZ charge of ion=+1 for k+/na+,+2 for ca2+,-1 for Cl-F Faraday's constantion= outside concentration of ion outside cell Nernst Equation at bodytempeture Eion=61.5/z time log[ion]outside/[ion]inside 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 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. Authorankurkum ID68214 Card Setneuroscience exam 2 lecture 2-12 Description2 slide 12 Updated2011-02-22T23:15:12Z Show Answers