Lec 4

Question 1

What is the Goldman Equation (simplified):

Answer 1

Ex = 58mV / z * log10 ([X]out / [X]in)

Question 2

Membrane Potential (Vm) is dependent primarily on its ________ to ions and thus the membrane potential will always fall between two equilibrium potentials. *Except* during electrophysiological experiment

a. Nernst potential E(k)
b. Permeability
c. neither

Answer 2

Permeability (Goldman Equation)

Question 3

Goldman Equation: If Px increases what will happen to the Vm?

increase or decrease?

Answer 3

increase

Question 4

1. Goldman Equation: Resting membrane potentials depend on the ionic gradients for what 3 ions?
2. Which is most important and, which is least important?

Answer 4

K+ – Most important

Na+

Cl- – Least Important

Question 5

When Vm = Ex , the net flow…

a. increases
b. decreases
c. is equal to 0
d. equal to infinity

Answer 5

C. Equal to zero

no driving force

Question 6

As Vm moves farther from Ex net flow will…

a. increase
b. decrease
c. stay the same
d. equal to 0

Answer 6

a. increase

driving force increases

Question 7

What is the equation for Driving Force?

Answer 7

Vm - Ex = Driving force

(part of Ohm’s law)

Ix = Gx(Vm-Ex)

Question 8

What would happen to EK if we increased the external concentration of KCl ?

Answer 8

EK would move closer to 0

*Note: high K+ inside the cell.

out - in would be closer to zero

Question 9

What would happen to EK if we decreased external concentration of KCl?

Answer 9

EK would become more negative

nernst Ek = -95 mV

out - in = more inside and greater difference

Question 10

What would happen to resting Vm if we decreased external concentration of KCl?

Answer 10

Vm will increase in negativity

* Ek will increase in negativity and so will Vm

Question 11

What would happen to EK if we increase external concentration of KCl?

Answer 11

Vm will move closer to zero

*EK will move closer to zero so will Vm

Question 12

What would happen to EK and Vm if we increased the number of K+ leak channels?

Answer 12

Vm would become more negative (increased Permeability)

and Ek would be unchanged

Question 13

What would happen to the EK and Vm if we decreased the number of K+ leak channels?

Answer 13

Vm would become more positive (decrease K+ permeability)

EK would be unchanged

Question 14

Which of these ions has the greatest driving force?

K+, Na+, Cl-

Answer 14

Na+

Vm - ENa = -64mV - +65 = 100 mV