Propagation of action potentials

Question 1

What is a nerve impulse?

Answer 1

an action potential that starts at one end of the neurone and is propagated along the axon to the other end of the neurone

Question 2

How is a action potential propagated?

Answer 2

the first region of the axon membrane is depolarised

this acts as a stimulus for the depolarisation of the next region of the membrane

the process continues along the length of the axon forming a wav eof depolarisation

Question 3

What happens as sodium ions are inside the axon?

Answer 3

they are attract by the negative charge ahead and the concentration gradient to diffuse further along inside the axon, triggering the depolarisation of the next section

Question 4

Why do channels open further down the axon?

Answer 4

due to the channels being voltage-gated

this causes further depolarisation

Question 5

What happens after the action potential has been propagated?

Answer 5

behind the new regions of depolarisation, the sodium voltage-gated channels close and the potassium ones open

potassium ions begin to leave the axon along their electrochemical gradient

the outward movement of the potassium ions has continued to the extent that hte axon membrane behind the action potential has returned to its original charged state

Question 6

What is the refactory period?

Answer 6

after an action potential there is a short period of time where the axon cannot be excited agian

voltage-gated soium ion channels remain closed, preventing the movement of sodium ions into an axon

Question 7

Why is the refactory period important?

Answer 7

prevents the propagation of an action potential backwards along the axon as well as forwards

the refactory period makes sure ation potential are undirectional

it also ensures that action potential don not overlap and occur as discrete impulses