Changing potential difference in the nervous system

Question 1

What charge is the outside and inside of an axon?

Answer 1

Outside = Positive
Inside = Negative

Question 2

What’s the potential difference when there’s no impulse (resting potential)?

Answer 2

-65 to -70 mV as it’s more negative inside the axon

Question 3

How to measure potential difference in an axon?

Answer 3

Microelectrodes, place one inside and one outside axon

Question 4

What’s the first process to happen after neurone is stimulated?

Answer 4

Depolarisation, sodium channels open and sodium ions diffuse into neurone. Inside becomes less negative

Question 5

What potential difference is threshold and what does it do?

Answer 5

• 55 mV, this opens all the sodium channels in the neurone

Question 6

How is depolarisation stopped?

Answer 6

When sodium channels close and potassium channels open

Question 7

How is repolarisation achieved?

Answer 7

Potassium ions diffusing out of the neurone

Question 8

How is hyperpolarisation achieved?

Answer 8

Closing of potassium ion channels is delayed, leads to potential difference being greater than resting potential

Question 9

How is resting potential reached after hyperpolarisation?

Answer 9

By the help of sodium potassium carrier protein

They’re more permeable to potassium ions than sodium ions so potassium ions diffuse into the axon faster than sodium ions are transported out

Question 10

Sodium potassium pump is what keeps resting potential constantly, explain how it does this:

Answer 10

The carrier protein uses ATP to actively transport:

-3 sodium ions out of the axon
-2 potassium ions into the axon

Larger positive charge in outside of axon compared to the inside