The Nerve Impulse: Resting Potential

Question 1

What is a nerve impulse?

Answer 1

A nerve impulse is a self propagating wave of electrical activity that travels along the axon membrane

Question 2

What is a resting potential?

Answer 2

A resting potential is when a neurone is not conducting an impulse, and there is a difference between the electrical charges inside and outside the neurone

Question 3

What is the resting potential value?
Why is this the resting potential value?

Answer 3

The resting potential value is -70mV. This is because there are more sodium ions and potassium ions on the outside of the neurone than on the inside. Therefore the inside of the neurone is comparatively negative

Question 4

How is a resting potential established?

Answer 4

The resting potential is established by the sodium - potassium pump

1/ The sodium - potassium pump actively transports sodium ions out of the axon and actively transports potassium into the axon. This is done in a three to two ratio, where three sodium ions are transported out and two potassium ions are transported out of the axon

2/ This movement creates an electrochemical gradient where there is a buildup of sodium ions on the outside and excess potassium ions on the inside

3/ This electrochemical gradient results in potassium ions diffusing out of the axon through potassium ion channels and sodium ions diffusing into the axon sodium ion channel (each moving from a region of high conc to lower conc)

4/ There is never a balanced amount of sodium ions and potassium ions because the membrane is more permeable to potassium ions resulting in more potassium ions moving out