Nerve impulses: transmission

Question 1

How is the impulse passed along the axon?

Answer 1

When a neurone is stimulated, the action potential does not actually travel along the axon, but instead triggers a sequence of action potential along the axon.
- Due to the insulation of the myelin sheath
( the refractory period allows it to travel in only one direction )

Question 2

What is the all or nothing rule?

Answer 2

States that the action potential only occurs if the stimulus causes enough sodium ions to enter the cell, to change the membrane potential to a certain threshold level.

If the depolarisation is not great enough to reach the threshold, then the action potential (and hence an impulse) will not be produced.

Question 3

What is a generator potential?

Answer 3

It occurs when a few channels open, and they allow a few sodium ions into the cell a produce a small action potential.