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Membrane Potential
Do all living cells have a membrane potential? - correct answer UMM YESH What is a membrane potential? - correct answer Difference in charge inside/outside the cell membrane What is electrical potential? - correct answer When opposite charges are separated they have the potential to do work if allowed to come together What 2 ways can electrical force increase? - correct answer Quantity of charge, decreased charge separation What is the RMP of a typical neuron? - correct answer -70mV Is it more positive or more negative inside the cell? - correct answer More NEGGY What acts as a great insulator in the cell? - correct answer Lipids (increase resistance) What is the definition of current? - correct answer Movement of charges How to decrease resistance? - correct answer Open ion channels What is Ohm's Law? - correct answer I=V/R Is the vast majority of ECF and ICF positive, negative, or neutral? - correct answer Neutral If the majority of ECF/ICF is neutral, what causes the membrane potential?? - correct answer Small "shell" of ions against the PM
What 2 things do the RMP depend on? - correct answer Difference in ion concentration between ECF/ICF, permeability of membrane to various ions What is step 1 of the membrane potential? - correct answer Na/K ATPase pumps set up/maintain Na/K concentration gradient How much Na is inside/outside the cell (at RMP)? - correct answer 15mM/150mM How much K is inside/outside the cell (at RMP)? - correct answer 150mM/5mM What is the definition of equilibrium potential? - correct answer Potential that opposes net diffusion of that ion through the PM What is the simplified Nernst equation? - correct answer Eion=61/Z log (conc out/conc in) How much does the Na/K pump contribute to the RMP? - correct answer 4mV How many Na/K do the Na/K pumps move in/out of the cell at once? - correct answer 3Na/2K What is step 2 of the RMP? - correct answer Greater net movement of K than Na makes RMP more negative on inside Why is there greater net movement of K than Na? - correct answer More K leak channels are open What two ways are K and Na moved into and out of the cell? - correct answer K leaks out, Na leaks in, K is pumped in, Na is pumped out
When is a good time to use the full GHK equation? - correct answer When a question asks about the Vm and Cl effects the Vm When is a good time to use the simplified GHK equation? - correct answer When a question is asking about the Vm but only K and Na effect the Vm Which ion has a higher membrane permeability (conductance): Na or K? - correct answer K!!! How can Ina and Ik be equal if K's conductance (permeability) is so much higher? - correct answer Na electrical gradient is bigger (further away from it's equilibrium potential) and thus the driving force is much larger. K-easier route, Na-wants it more What is the modified Ohm's law? - correct answer I = g (Vm - Eion) (where g = permeability) Which way will K flow when: Ek = -90mV, Vm = +30mV - correct answer OUT (wants Vm more negative, will flow out b/c it is positive) Which way will K flow when: Ek = -90mV, Vm = -120mV - correct answer IN (wants Vm more positive than -120mV, will flow in b/c it is positive) Which way will Na flow when: Ena = +60mV, Vm = -90mV - correct answer IN (want Vm more positive than -90mV, will flow in b/c it is positive) Which way will Cl flow when: Ecl = -70mV, Vm = -90mV - correct answer OUT (want Vm more positive than -70mV, will flow out b/c it is negative) If there was a cell with equal concentrations of Na and Cl inside and outside, and then all of a sudden a whole bunch of negative charge was added to the ICF, what would happen assuming permeability of only Cl and NOT Na? - correct answer Cl would leave At steady state, is there ever a NET flux of ions? - correct answer NONONONONO!!!!!!
What would happen to the RMP if the concentration of Na in the ECF is increased? - correct answer Increased Na conc grad, Na into cell, increased +charges inside cell, RMP = more + What would happen to the RMP if the concentration of K in the ECF is increased? - correct answer Decreased K conc grad, less K out of cell, accumulation of more + charges inside cell, RMP = more + What would happen to the RMP if the concentration of Cl in the ECF is increased? - correct answer Increased Cl conc grad, more Cl into cell, increased -charges into the cell, RMP = more -
