Passage Of An Action Potential

Question 0

How are the action potentials regenerated along each small region of the axon membrane?

Answer 0

As one region of the axon produces an action potential and becomes depolarised, it acts as a stimulus for the depolarisation of the next region of the axon

Question 1

How does the action potential move along the axon?

Answer 1

The reversal of electrical charges that are reproduced at different points along the axon membrane

Question 2

What is the movement of a action potential sometimes compared to?

Answer 2

A Mexican wave

Question 3

Outline the first stage of the passage of an action potential along an unmyelinated axon?

Answer 3

At resting potential the concentration of sodium ions outside the axon membrane is high relative to the inside, whereas that of the potassium ions is high inside the membrane relative to the outside. The axon membrane is polarised.

Question 4

Outline the second stage

Answer 4

A stimulus causes a sudden influx of sodium ions and hence a reversal of charge on the axon membrane. This is action potential and the membrane is depolarised

Question 5

Outline the third stage

Answer 5

The localised electrical circuits established by the influx of sodium ions causes the opening of sodium voltage-gated channels which causes depolarisation. Behind this region of depolarisation, the sodium voltage-gated channels close and the potassium ones open and the potassium ions begin to leave the axon

Question 6

Outline the fourth stage

Answer 6

The action potential (depolarisation) is propagated in the same way further along the axon. The outward movement of the potassium ions has continued to the extent that the axon membrane behind the action potential has returned to its original charged state (It has been repolarised)

Question 7

Outline the fifth and final stage?

Answer 7

The repolarisation of the axon allows sodium ions to be actively transported out, once again returning the axon to its resting potential in readiness for a new stimulus

Question 8

In myelinated axons, what is the purpose of the fatty sheath?

Answer 8

It acts as an electrical insulator that prevents action potentials from forming

Question 9

At what points on a myelinated axon can action potentials occur?

Answer 9

The nodes of Ranvier

Question 10

How are action potentials transferred along a myelinated axon?

Answer 10

They travel via localised circuits between adjacent nodes of Ranvier and the action potentials effectively ‘jump’ from node to node in a process known as saltatory conduction

Question 11

Do action potentials pass along myelinated or unmyelinated axons faster?

Answer 11

Myelinated