Ionic basis of the action potential

Question 1

What is the Na+ and K+ equilibrium potential?

Answer 1

the membrane potential at which there is no movement of the ions in or out of the cell

Question 2

What effect does Na+ and K+ have on the membrane potential?

Answer 2

• a cell only permeable to K+ will have a negative membrane potential
• a cell only permeable to Na+ will have a positive membrane potential

Question 3

What is depolarisation?

Answer 3

loss of difference in charge between the inside and outside of the plasma membrane due to a change in permeability

Question 4

What is repolarisation?

Answer 4

change in membrane potential that returns it to a negative value

Question 5

What is hyperpolarisation?

Answer 5

a change in the membrane potential that makes it more negative (opposite of depolarisation)

Question 6

What is Ohm’s law?

Answer 6

electric current is proportional to voltage and inversely proportional to resistance

Question 7

What happens if you inject a positive current into a non-excitable cell?

Answer 7

the membrane potential will readjust to a new eqilibrium

Question 8

What happens if you inject positive current into an excitable cell?

Answer 8

you start to depolarise the membrane

Question 9

What is PNa+?

Answer 9

permeability to sodium

Question 10

What happens when Na+ channels open?

Answer 10

• increased Na+ permeability
• increased flow of Na+ into cell
• membrane depolarisation