6.3 The resting membrane potential

Question 1

What is membrane most permeable to at rest?

Answer 1

Potassium

Question 2

Consequences (3)

Answer 2

• permeability to Na+ means RMP more + than Ek
• Pk» P(Na) (40 fold) so RMP closer to Ek than E(Na)
• if P(Na) increases then RMP will be more +

Question 3

Why is RMP not same as Ek?

Answer 3

Na+ can also pass membrane

with negative RMP Na+ will enter cell down both electrical and concentration gradients

Na+ will only be at equilibrium at Na equilibrium potential- E(Na)= +61.5mV

Question 4

Does chloride change membrane potential value?

Answer 4

No

Question 4

RMP

Answer 4

-65mV because no ion at equilibrium influx

Question 5

Why does potassium concentration remain constant?

Answer 5

hardly any ion movement required to charge capacitor and set up membrane potential

almost no change in ion concentration (0.006% of K+ ions leave)

Question 6

Capacitors

Answer 6

• device for storing energy via separation of electrical charge
• charge “stored” on 2 plates separated by insulator

eg: lighting

Question 7

Goldman-Hodgkin-Katz (GHK) Equation

Answer 7

• allows us to calculate the resting membrane potential
• if only one ion can permeate the membrane, then the equation simplifies to the Nernst equation for that ion
• P= permeability