Action Potential Propagation

Question 1

What are the 2 types of action potential (AP) propagation discussed?

Answer 1

• continuous
• saltatory

Question 2

Where does an action potential propagation develop?

Answer 2

Initial segment after the axon hillock

Question 3

Where does continuous propagation occur?

Answer 3

unmyelinated axons

Question 4

How do APs travel across an unmyelinated neurone?

Answer 4

1) as AP develops, transmembrame potential depolarises to +30 mV

2) a local current depolarises the adjacent portion of the membrane to threshold

Question 5

How do APs travel across an myelinated neurone?

Answer 5

3) as AP develops, initial segment enters refractory period

4) local current depolarises the adjacent portion of the membrane to threshold, and cycle repeats

Question 6

How do myelinated fibres affect membrane potential?

Answer 6

• insulating sheath restricts the MP to the nodes
• ions can only cross the membrane at these nodes

Question 7

Draw a diagram of a myelinated axon

Answer 7

• myelin
• Node of Ranvier
  (slide 5)

Question 8

What is saltatory propagation?

Answer 8

AP travels rapidly down a myelinated axon, jumping from one node of Ranvier to the next

Question 9

How does saltatory propagation differ from continuous propagation?

Answer 9

• (myelinated:) ions can only cross the membrane at the nodes
• local currents propagate the current rapidly from node to node

Question 10

Why is saltatory propagation faster than continuous propagation?

Answer 10

• impulse ‘jumps’ from node to node
• uses less energy because fewer ions cross the membrane

Question 11

How does conduction velocity differ in myelinated and unmyelinated nerves?

Answer 11

higher in myelinated

Question 12

Summarise the difference and similarities between graded and action potentials

Answer 12

slide 9