Lecture #4: Resting Potential

Question 1

What ions does the extracellular fluid primarily contain?

Answer 1

Na+

Cl-

Question 2

What ions does the cytoplasm primarily contain?

Answer 2

K+

Cl-

Question 3

What does the Na/K ATPase do?

Answer 3

pump 3 Na+ out

2 K+ in

Question 4

How is the resting potential generated? Is it active or passive?

Answer 4

movement of ion through ion channels, down their concentration gradients
passive

Question 5

What two conditions are present at the equilibrium potential?

Answer 5

1. chemical force (concentration difference) = electrical driving force (net flux = 0)
2. Ionic movement of K+ from 1 to 2 = Ionic movement of K+ from 2 to 1

Question 6

What equation is used to find the resting potential?

Answer 6

Nernst

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

Question 7

What does interstitial hyperkalemia lead to? What does interstitial hypokalemia lead to?

Answer 7

Hyperkalemia –> cellular depolarization

Hypokalemia –> cellular hyperpolarization

Question 8

The membrane potential is proportional to the _____

Answer 8

ion gradient

Question 9

What is the slope of a graph of membrane potential versus the log of the concnetration gradient?

Answer 9

50mV/decade change in concentration gradient

Question 10

What does increasing [K+]o cause?

Answer 10

depolarization of the membrane

Question 11

larger gradients lead to _____ of the membrane

Answer 11

larger polarization

Question 12

________ to K+ is cause by K+ permeable membrane channels which are open in _____ and stay open _____

Answer 12

• Selective permeability
• Resting neurons
• All the time

Question 13

There is more K+ _____ the neuron than ____ because of the Na/K Pump

Answer 13

inside

outside

Question 14

The resting potential across the membrane represents an _______ between the concentration gradient of ___ and an opposing electrical gradient

Answer 14

• Electrochemical equilibrium

- K+

Question 15

The resting potential to a cell only permeable to K+ is an _____ and can be calculated with the _____

Answer 15

• equilibrium potential

- Nernst equation

Question 16

The basic mehcnaism underlying resting membrane potential can be understood in an “ideal cell” in which a membrane ______ to K+ divides solutions with _____ of K+

Answer 16

• only permeable

- different concentrations

Question 17

To find a more realistic resting potential of a cell permeable to both K+ and Na+, what equation is used?

Answer 17

Goldman equation

Question 18

What two things does the Goldman equation take into account?

Answer 18

• concentration of ion

- permeability of membrane for ions

Question 19

The rate of change of membrane potential is set by the membrane ______

Answer 19

capacitance

Question 20

The magnitude of the change in membrane potential is set by the membrane ______

Answer 20

conductance

Question 21

In a realistic cell, the membrane potential is a _____ - not an equilibrium potential

Answer 21

steady state potential