Resting Potential

Question 1

electric voltage across cell membrane

Answer 1

• results from separation of positive and negative charges across the cell membrane
• gives rise to membrane potential
• charge across membrane over capacitance (amount of electrical energy separated for a given electric potential)
• dielectric (membrane) separates the ECF and ICF that are conductors
• static electric field is resting membrane potential
• number of neg and pos ions outside virtually equal because very small K leakage
• and the separation makes the potential

Question 2

depolarization

Answer 2

• reduction in charge separation

- less negative membrane potential

Question 3

hyperpolarization

Answer 3

• increase in charge separation

- more negative membrane potential

Question 4

ionic gradients

Answer 4

• two major players in generation of potentials:
• ion pumps-make gradients
• ion channels- movement to reach electrochemical equilibrium
• nerve cell is surrounded by a lipid bilayer that contains ion channels and pumps
• ECF has Na and Cl
• ICF has K and Cl

Question 5

ion movement

Answer 5

• electrical potentials result from movement of ions down their concentration gradients, through channels, charging the membrane capacitance
• ion channels are membrane proteins for specific ions
• direction of current is direction of net movement of positive charge
• selective gating can generate- AP, synaptic potentials, receptor potentials

Question 6

diffusion potential

Answer 6

• potential difference generated across a membrane when a charged solute diffuses down its concentration gradient
• some ions move down concentration gradient and change membrane potential but effective concentration remains the same- puts Na at electrochemical equilibrium

Question 7

equilibrium potential

Answer 7

-if there is a concentration difference for an ion, a potential difference is created

Question 8

resting potential in K cells

Answer 8

• chemical (concentration difference) force = electrical DF
• ionic movement of K from 1-2= ionic movement from 2-1
• calculated using nernst equation
• at equilibrium- negative buildup inside- impedes further efflux of K
• no net flux
• potential is electrochemical equilibrium

Question 9

nernst equation

Answer 9

E= [58/z]log [X2/X1]

-Ek is -58 mV

Question 10

interstitial hyperkalemia

Answer 10

• higher K outside cells
• less negative membrane
• depolarization

Question 11

interstitial hypokalemia

Answer 11

• lower K outside cells
• more neg membrane
• hyperpolarization

Question 12

resting potential with K and Na cells (single)

Answer 12

Ek is -58

-En is +58

Question 13

the goldman equation (both Na and K)

Answer 13

-resting potential determined by K and Na
-not equal to Ek
-Vm=58log[(Ko+aNao)/(Ki+aNai)]
a=PNa/Pk
-more permeable ions have a bigger effect on the membrane potential
-Pk»PNa
-can include Cl too

Question 14

Pk:PNa:Pcl

Answer 14

• 1:0.04:0.45 in resting cell
• at peak of AP- 1:20:0.45- Na perm increases at AP
• small Pna at rest explains difference in Ek and Vm at rest

Question 15

summary

Answer 15

• membrane of resting neurons more permeable to K than any other ion
• resting potential determined by K and some Na and some Cl
• membrane potential not = Ek because of perms- goldman
• concentration gradients and perm
• goldman- resting- at steady state-no net flow of current- pump is equalized by K channels and Na leak channels- (permeable to both but Na has bigger gradient)