Lecture 22: Membrane potentials

Question 1

The resting membrane is determined by what cations on either sides of the membrane?

Answer 1

Na + and K+

Question 2

The membrane is selective and impermeable to ions so how do Na+ and K+ cross the membrane?

Answer 2

Via specific protein carriers, channels and pumps

Question 3

The RMP of -70mv is maintained by what?

Answer 3

Sodium - Potassium pump which pumps 3Na+ OUT of the cell for every 2K+ IN ——> maintains RMP - slight imbalance of ionic charges across the membrane

Question 4

How many Na+ are pumped OUT of the cell?

Answer 4

3 Na+ are pumped OUT of the cell by Na+/K+ pump

Question 5

How many K+ are pumped IN to the cell

Answer 5

2 K+ are pumped IN to the cell by Na+/K+ pump

Question 6

What is a local potential?

Answer 6

A temporal fluctuation in a local region fo the membrane

- occurs when Na+ and K+ channels open

Question 7

How does a depolarised (excitatory) potential occur?

Answer 7

When Na+ channels open ——> positive charge moves IN

RMP becomes more positive

Question 8

How do repolarised potentials occur?

Answer 8

When K+ channels open ——> positive charge moves OUT

RMP become more negative

Question 9

How do hyper polarised (inhibitory) potentials occur?

Answer 9

RMP exceeds -70mv e.g -80mv

- Na+/K+ ATPase pump then brings value back to -70mv