CMB1004/L09 Action Potential

Question 1

Name the 3 phases to action potential.

Answer 1

Depolarisation
Repolarisation
Hyperpolarisation

Question 2

Name the 2 voltage-gated channels involved in action potential.

Answer 2

Voltage-gated Na+ channel
Voltage-gated K+ channel

Question 3

What is the voltage at which all voltage-gated Na+ channels open?

Answer 3

Threshold voltage

Question 4

What happens when voltage-gated Na+ channels are inactive?

Answer 4

They are impermeable to Na+ ions

Question 5

At approximately what voltage do voltage-gated Na+ channels open?

Answer 5

-55mV

Question 6

Are activation and inactivation gates separate parts of the protein?

Answer 6

Yes
Activation gate - voltage-dependent
Inactivation gate - time-dependent

Question 7

Which of the voltage-gated channels has an inactivation gate?

Answer 7

Voltage-gated Na+ channel

Question 8

What is the absolute refractory period?

Answer 8

The period in which the membrane cannot generate another action potential no matter how big the stimulus

Question 9

What is the relative refractory period?

Answer 9

The period in which the membrane can generate another action potential but only if the stimulus is bigger than normal

Question 10

What state are voltage-gated Na+ channels in during the absolute refractory period?

Answer 10

Inactivated

Question 11

What state are voltage-gated Na+ and K+ channels in during the relative refractory period?

Answer 11

Na+ - some recovered
Na+ - some inactivated
K+ still open

Question 12

What prevents the action potential from being set off backwards?

Answer 12

The refractory period