Lecture 4

Question 1

Define resting membrane potential

Answer 1

Difference in potential energy between two sides of cell membrane resulting from chemical and electrical gradients

Question 2

Define chemical energy in terms of the RMP

Answer 2

Different concentrations of ions on each side of the cell, creating chemical gradients

Question 3

Define electrical energy in terms of the RMP

Answer 3

Different amounts of negative charges on each side of the cell, creating electrical gradient

Question 4

What is the typical RMP range for neurons, muscle cells, and glial cells?

Answer 4

-60 to -90 mV

Question 5

What is the typical RMP range for non-excitable cells (e.g. epithelial cell and red blood cells)?

Answer 5

-8 to -60 mV

Question 6

How is resting membrane potential established?

Answer 6

Ion pumps and exchangers

Question 7

How are ion pumps powered?

Answer 7

ATP

Question 8

How are ion exchangers powered?

Answer 8

Ion concentration gradients

Question 9

Is K+ more abundant inside or outside a cell?

Answer 9

Inside

Question 10

Is Na+ more abundant inside or outside a cell?

Answer 10

Outside

Question 11

Is Ca2+ more abundant inside or outside a cell?

Answer 11

Outside (extremely low inside)

Question 12

Is Cl- more abundant inside or outside a cell?

Answer 12

Variable

Question 13

Are anions larger or smaller inside the cell?

Answer 13

Larger (e.g. DNA, RNA, proteins)

Question 14

Are anions larger or smaller outside the cell?

Answer 14

Smaller (e.g. Cl- and bicarbonate HCO3-)

Question 15

In seawater animals, how do ion concentrations differ? (3)

Answer 15

Double ion concentrations
K+ more abundant inside
Na+ more abundant outside

Question 16

Define chemical potential energy

Answer 16

Potential energy produced by ion concentration differences across cell membrane

Question 17

Define electrical potential energy

Answer 17

Potential energy produced by charge concentration differences across cell membrane

Question 18

Define electrochemical potential energy

Answer 18

Chemical + electrical potential energies

Question 19

What happens at E_ion?

Answer 19

No net movement of ion (i.e. inward = outward flow)

Question 20

What does the Nernst equation describe?

Answer 20

Membrane voltage at which ion is at equilibrium

Question 21

Ions with higher conductances…

Answer 21

are better at “pulling” RMP towards their E_ion

Question 22

What ion typically determines RMP?

Answer 22

K+

Question 23

At low levels of K+_out, what happens to V_m?

Answer 23

Does not decrease linearly with K+_out because the driving force for Na+ increases as V_m increases in difference from E_Na

Question 24

What happens when i_ion is negative?

Answer 24

Ion flows into cell since V_m is lower than E_ion (increases V_m)

Question 25

What happens when i_ion is positive?

Answer 25

Ion flows out of cell since V_m is higher than E_ion (decreases V_m)

Question 26

What is membrane voltage determined by?

Answer 26

Equibilbrium potentials of all ions that can transverse membrane and their conductance at that point in time

Question 27

What are the two assumptions of the Goldman, Hodgkin, and Katz (constant field) equation?

Answer 27

1. Cl- is at equilibrium

2. At rest, i_K = i_Na

Question 28

Define permeability

Answer 28

Ease at which ions can pass through an open channel

Question 29

Define conductance

Answer 29

Permeability + availability of ions

Question 30

What is the Mullins and Noda modification of the GHK/constant field equation?

Answer 30

i_Na:i_K ratio = 3:2