Action Potential

Question 1

Where is an action potential produced

Answer 1

Axon hillock (next to soma)

Question 2

Define depolarisation

Answer 2

A change in electrical potential of the inside relative to the outside

Question 3

Resting membrane potential of inside?

Answer 3

-50 to -80 mV

Question 4

How is potential difference maintained at resting

Answer 4

1. Due to difference in conc of K+ and Na+ ions across membrane
2. Na/K pump (ATP) pumps 2K+ in for every 3Na+ out

Question 5

Describe depolarisation

Answer 5

1. Some Na+ voltage-gated channels open causing an influx of Na+ ions
2. If threshold met (-55mv) all Na+ channels open
3. Due to high conc gradient Na+ floods into axon very fast

Question 6

Describe repolarisation

Answer 6

1. At peak membrane potential (+30mv)
2. Na+ channels close
3. K+ voltage-gated channels open (flood out down conc gradient)
4. Causes hyperpolarisation

Question 7

Two types of refractory period

Answer 7

1. Absolute: Na+ channels deactivate

2. Relative: hyperpolarisation means further away from threshold so less likely to fire

Question 8

Describe gaps in Myelin

Answer 8

1. Nodes of Ranvier
2. Ion channels are concentrated
3. Allows saltatory conduction: Na+ ions diffuse rapidly from one node to the next