resting potential

Question 1

what is a membrane potential and what is it caused by?

Answer 1

it is the static electric field developed by the separation of positive and negative charges across the cell membrane

Question 2

what is depolarization?

Answer 2

a decrease in charge separation and a less negative membrane potential

Question 3

what is hyperpolarization?

Answer 3

an increase in charge separation and more negative membrane potential

Question 4

what is the capacitance?

Answer 4

the amount of electrical energy separated for a given electrical potential (C=Q/V)

Question 5

what are the conductors and the dielectric in respect to membrane potential?

Answer 5

the conductors are the ECF and ICF and the dielectric is the membrane

Question 6

how many K+ ions must be transferred inside the membrane to create the resting membrane potential?

Answer 6

very few (1/200,000 K+ into the cell)
does not change the concentration in the bulk solution

Question 7

what is the relative ion concentration inside and outside the cell for K, Na and Ca? Which plays the primary role in generating a resting potential?

Answer 7

K in>K out (generates resting potential)

Na in«Ca out

Question 8

what is the direction of current flow?

Answer 8

the direction of net movement of positive charge

Question 9

what type of transport generates resting potential? what other potentials do they create?

Answer 9

passive transport with selective gating channels

action, synaptic and receptor potentials

Question 10

what is a diffusion potential?

Answer 10

the difference generated across a membrane when a charged solute diffuses down the concentration gradient

Question 11

what is an equilibrium potential?

Answer 11

extension of diffusion principal
if there is a concentration difference for an ion across a membrane and the membrane is permeable, a potential difference occurs

Question 12

what is electrochemical equilibrium?

Answer 12

when chemical and electrical driving forces are equal and opposite

Question 13

if there are two concentrations of KCl across a membrane permeable only to K, what will happen? In what cells does this occur?

Answer 13

a membrane potential difference develops across the membrane (negative difference in the cell) and reaches equilibrium
occurs in glial cells

Question 14

what is the Nernst equation and what does it calculate?

Answer 14

E=(RT/zF)ln([X2]/[X1])=(58/z)log([X2]/[X1])

calculates the potential across a membrane that is permeable to only one ion

Question 15

what is the result of interstitial hyperkalemia and hypokalemia on the cell?

Answer 15

hyper-cellular depolarization

hypo- cellular hyperpolarization

Question 16

what is a more realistic cell model of resting potential?

Answer 16

membrane has various ion channels that are permeable to K, Na and Cl
the membrane potential is not equal to the equilibrium potential to K

Question 17

what equation is used to calculate the membrane potential with contributions from multiple ions? what does it include?

Answer 17

the goldman equation

it includes the permeability of each ion and its concentration on either side of the cell membrane

Question 18

when does an ion have greater influence in determining the membrane potential?

Answer 18

when it has greater permeability across the membrane

Question 19

what is alpha?

Answer 19

the permeability of sodium divided by the permeability of potassium (potassium is 25x more permeable)

Question 20

what is different about Cl in the goldman equation?

Answer 20

the Cl inside is in the numerator instead of the denominator because it has a negative charge

Question 21

in a squid giant axon, why is the theoretical Ek so different from the measured Vm (resting potential)?

Answer 21

because Ek does not take sodium ions into account (steady state potential instead of an equilibrium potential)