Membrane Electrophysiology: Resting Membrane Potential

Question 1

What is a membrane potential?

Answer 1

separation of charges across plasma membrane

Question 2

What are the key ions involved in membrane potential?

Answer 2

Ca2+, Na2+, K+, Cl-

Question 3

When is a resting membrane potential established?

Answer 3

when cell is not sending signals

Question 4

Why is a resting membrane potential important?

Answer 4

in general, is important for transport processes involving movement of charges

Question 5

What is the general RMP range for skeletal, cardiac, and nerve cells?

Answer 5

-60 to -90 mV

Question 6

What factors contribute to the RMP?

Answer 6

• intracellular anions
• Na+/K+ pump (indirect contribution)
• diffusion potential of permeable ions

Question 7

What ion will have the greatest contribution/effect on the RMP?

Answer 7

the ion with greatest permeability

Question 8

Define electrogenic.

Answer 8

net movement of charge across cell membrane

Question 9

Define diffusion potential.

Answer 9

potential difference across cell membrane due to concentration difference of an ion, dependent on size of concentration gradient.

Question 10

What forces act on an ion?

Answer 10

• concentration (chemical) force
• electrical foce.

it is the sum/difference of these two forces that determine the net movement of the ion

Question 11

Define electrochemical equilibrium

Answer 11

when chemical and electrical forces acting on an ion are equal and opposite causing zero net diffusion of ion.

Question 12

Define equilibrium potential.

Answer 12

diffusion potential (mV) at which the concentration gradient’s promotion of diffusion is opposed

• size based on ions charge and distribution
• magnitude is based on concentration gradient

Question 13

What is the function of the Nernst equation?

Answer 13

to predict the equilibrium potential for any concentration gradient of an ion - aka what the membrane potential would be for the ion to be at electrochemical equilibrium

Question 14

What is the rate of ion diffusion depend on?

Answer 14

1. external and internal concentration of ions
2. transmembrane voltage
3. permeability of ion

Question 15

Define membrane conductance.

Answer 15

the ease/ability for ion to pass through membrane. (if channels are open, conductance increases)

Question 16

What are the three main classifications of ion channels?

Answer 16

• ungated
• voltage-gated
• ligand-gated

Question 17

What ion has the greatest effect on the resting membrane potential: Na+ or K+?

Answer 17

K+

Question 18

How do excitable cells generate action potentials?

Answer 18

by transiently increasing Na+ or Ca2+ permeability driving Vm in a positive direction