Action Potential Propagation

Question 1

What is AP Propagation?

Answer 1

The process whereby action potentials travel from one end of nerve axon to the other in a continuous flow.

Question 2

What sheath surrounds certain nerve axons and in what pattern?

Answer 2

A sheath of myelin in concentric layers

Question 3

Is the myelin sheath continuous?

Answer 3

No it is intermittent.

Question 4

What are the intermittent spaces in the myelin sheath called?

Answer 4

Nodes of Ranvier

Question 5

What is the significance of the Nodes of Ranvier?

Answer 5

Current can only pass through nodes of ranvier and so action potentials are only generated here in myelinated nerves

Question 6

Action potentials due to this arrangement appear to jump from one node to the next, this is called?

Answer 6

Saltatory Conduction

Question 7

What is the effect of this arrangement and of Saltatory Conduction?

Answer 7

Myelinated nerves transmit information much faster as only a small section of axon needs to be depolarised

Question 8

Conduction velocity is also influenced by diameter of nerve axon and so the larger the diameter…

Answer 8

the faster the conduction speed.

Question 9

This means that?

Answer 9

Large, myelinated nerves are the fastest - 100m/s

Smaller, non-myelinated nerves are slowest 2/ms

Question 10

Describe the process that occurs when an AP reaches the Axon terminal.

Answer 10

• terminal region depolarises
• calcium channels open allowed diffusion of calcium molecules into terminal
• This causes small vesicles or synaptic vesicles to fuse with the terminal membrane
• These vesicles contain neurotransmitters
• Neuro transmitters released in synaptic cleft
• Axon terminal in close contact with other nerve axon or with muscle cell
• Neurotransmiter binds to receptors and open gated ion channels in post-synaptic cell
• Depending on which cell and the neurotransmitters released this neighbour cell is either depolarised(switch on) or hyper polarised (switch off)

Question 11

How does Local anaesthetic work in relation to action potentials?

Answer 11

Local anaesthetic works by reversibly blocking action potential propagation

Question 12

How does Local anaesthetic work in relation to action potentials?

Answer 12

Local anaesthetic works by reversibly blocking action potential propagation