1 L5 Action Potentials

Question 1

What kind of channels does the base of the axon have a high concentration of

Answer 1

Voltage gated sodium channels

Question 2

Describe the relative speed of voltage gated Na and K channels

Answer 2

Voltage gated Na channels open quickly in relation to K channels which are slower

Question 3

Describe the voltage gated K channel subunit

Answer 3

It is charged and changes configuration when the voltage across the protein changes

Question 4

What causes the ‘undershoot’ of voltage going below RMP and closer to EK

Answer 4

The slow kinetics of the voltage gated K channel- K conductance stays high

Question 5

Describe the absolute refractory period

Answer 5

No matter how large the stimulus, another AP can not be generated since VG Na channels are inactivated

Question 6

What is the purpose of refractory periods

Answer 6

Prevents AP from propagating backwards

Question 7

Describe the relative refractory period

Answer 7

An AP can be generated but only in response to a very large stimulus because depolarisation of stimulus dampened by relative high K permeability at point in time

Question 8

Describe key features of refractory periods

Answer 8

Inactive Na channels do not allow Na passage. Without high Na conductance, membrane cannot be depolarised. Na channels are reactivated as MP reaches RMP

Question 9

Compare and contrast relative size of LP and AP

Answer 9

LP- Graded- vary in size and duration, can be small and big
AP- normally same size, described as all or none (either get one or you don’t)