8 - Neurone response to stimulation

Question 1

Stimulus

Answer 1

Stimulus excites the neurone cell membrane, causing sodium ion channels to open. It becomes more permeable to sodium, so sodium ions diffuse into the neurone down the sodium ion electrochemical gradient.

Question 2

Depolarisation

Answer 2

-If the potential difference reaches the threshold (around -55mV), more sodium ion channels open.
- Therefore, more sodium ions diffuse into the neurone.

Question 3

Repolarisation

Answer 3

-At a potential difference of around +30mV the sodium ion channels close and potassium ion channels open.
-The membrane is more permeable to potassium so potassium ions diffuse out of the neurone down the potassium ion conc. gradient. Starting to get the membrane back to its resting potential

Question 4

Hyperpolarisation

Answer 4

Potassium ion channels are slow to close so there’s a slight overshoot where too many potassium ions diffuse out of the neurone. The potential difference becomes more negative than the resting potential (less than -70mV)

Question 5

Resting potential

Answer 5

• the ion channels are reset.
• the sodium-potassium pump returns the membrane to its resting potential and maintains it until the membrane’s excited by another stimulus.