Question

Neurology questions: Membrane potentials

Answer the 3 following

1- In an experiment about the action potential, what kind of effect does changing E_k to a more negative value (-95) has on the action potential?

a) The inflection point was observed too early

b) The peak of the graph decreased

c) The lowest point of the graph (undershoot) turned more negative

d) The threshold decreased

Explain your answer:

2- Under what conditions would E_k be more positive?

a) The internal concentration of potassium = External concentration of potassium

b) The internal concentration of potassium < External concentration of potassium

c) The internal concentration of potassium > External concentration of potassium

d) The internal concentration of potassium < External concentration of sodium

Explain your answer:

3- If the extracellular concentration of potassium was 70 mM, which would need to be the intracellular concentration so that E_k= 0 ?

a) 70 mM

b) 7 mM

c) 700 mM

Explain your answer:

Answer 1

1. Answer: C

undershoot of the action potential represents hyperpolarisation. That is more efflux of K+ ions occurs which causes the resting membrane potential more negative

2. Answer: C

Intermal concentration of potassium > External concentration of potassium

The membrane becomes more permeable to K+ which causes potassium iinto the cell. The entry of K+ becomes more positive disturbs the resting membrane potential and causes the inside of the cell becomes more positive

3. Answer: B

Ek = - RT/FZ ln {ion} out/{ion} in