The Resting Membrane Potential

Question 1

Define membrane potential

Answer 1

magnitude of electrical charge inside the cell relative to the extracellular solution = mV

Question 2

How can you measure MP?

Answer 2

microelectrode penetrates cell membrane, conducting solution, mV taken

Question 3

Generating MP requires 2 factors, what are they?

Answer 3

Asymmetric distribution of ions across PM and selective ion channels

Question 4

Which ion dominates the membranes permeability the most?

Answer 4

K+, due to open K+ channels

Question 5

Describe the electrical vs the chemical gradient for K+

Answer 5

Towards inside: electrical gradient for K+, +ve attracted to –ve anions

Towards outside: chemical (diffusion) gradient for K+, high to low conc

Question 6

Which equation can be used to calculate the equilibrium potential?

Answer 6

Nernst equation

Question 7

Which ions are higher in conc inside?

Answer 7

K+ and A- (all other anions)

Question 8

What will increasing the permeability for a particular ion do to the equilibrium potential for that ion?

Answer 8

Move it closer to the equilibrium potential

Question 9

What is the Nerst equation at 37C?

Answer 9

61/valency x log10 x [K]o/[K]i

Question 10

What is the resting MP of a nerve?

Answer 10

-70mV

Question 11

What is the resting MP of a cardiac cell?

Answer 11

-90mV

Question 12

What is selective permeability?

Answer 12

Different cells have different channels present allowing different amounts of ions in/out: ion channels

Question 13

What is equilibrium potential?

Answer 13

MP at which the ion will be in equilibrium, given the extra/intra concs

Question 14

If the membrane is selectively permeable to one ion where will MP be?

Answer 14

Equilibrium potential (nernst equation)

Question 15

Which ions are higher in conc outside?

Answer 15

Na+, Cl-, Ca2+

Question 16

How does the resting membrane potential arise?

Answer 16

the membrane is selectively permeable to K+ = there will be a -ve charge across the membrane due to K+ movement out of the cell

Question 17

What is the electrochemical gradient?

Answer 17

2 part gradient

chemical gradient = diff in solute conc across a membrane

electrical gradient = diff in charge across a membrane

Question 18

What is the phospholipid bilayer permeable and impermeable to?

Answer 18

permeable = small uncharged molecules

impermeable = charged molecules

Question 19

What is the resting MP of a skeletal cell?

Answer 19

-90mV

Question 20

Why do some cells have lower resting potentials?

Answer 20

Lower selectivity for K+