Lecture 4.1: The action potential and its properties

Question 1

Ways of investigating the mechanism of action potential generation (3)

Answer 1

• Voltage-clamping controls the membrane potential so
  that the ionic currents can be measured
• Using different ionic concentrations the contribution
  of various ions can be assessed
• Patch-clamping enables currents flowing through
  individual ion channels to be measured

Question 2

What happens during the upstroke
(depolarisation) of the AP ?

Answer 2

• Na+ channels open
• Na+enters the cell
• Cell is depolarised

Question 3

What happens during the downstroke (repolarisation) of the AP ?

Answer 3

• Opens K+ channels
• K+ efflux
• Inactivates Na+ channels
• Na+ infflux stopped
• Repolarisation of cell occurs

Question 4

Recovery after an action potential: What is ARP?

Answer 4

Absolute Refractory Period
Nearly all Na+ channels are in the inactivated state

Question 5

Recovery after an action potential: What is RRP?

Answer 5

Relative Refractory Period
Na+ channels are recovering from inactivation, the excitability returns towards normal as the number of channels in the inactivated state decreases