4.2 Conduction of the Nerve Impulse

Question 0

Explain the importance of having different diameter axons of nerve cells within a neurone.

Answer 0

Action potentials travel at different speeds down axons with different diameters. This allows depolarisation to last for longer.

Question 1

Name a disease caused by the breakdown of the myelin sheath

Answer 1

Multiple Sclerosis- all CNS nerves

Devio’s disease- optic and spinal nerves

Question 2

Explain local current theory

Answer 2

Injection of a current into the membrane will cause the nearby membrane to depolarise. The further the membrane from the injection of current, the less it will be depolarised.

Question 3

Why does a myelinated axon conduct faster than an umyelinated axon?

Answer 3

In myelinated axons, the Na+ channels are concentrated to the Nodes of Ranvier. A smaller area of membrane must depolarise. The action potential can jump between nodes.

Question 4

Describe ‘saltatory conduction’

Answer 4

Saltatory conduction is when the action potential ‘jumps’ between the Nodes of Ranvier to conduct the impulse much quicker.

Question 5

State a consequence of demyelination

Answer 5

Loss of movement