Lecture 4 - Action Potentials

Question 1

What are the characteristics of an action potential?

Answer 1

• all-or-none; an action potential either occurs or it doesn’t
• self propagating; a region of depolarization generates and action potential in the region next to it
• non-decremental; does not decrease in strength

Question 2

What are the different configurations of the gates on a sodium channel and in what conditions do the states occur?

Answer 2

• resting state; activation gate closed, inactivation gate open; (-90 mV)
• activated state; activation gate open, inactivation gate open; (-90 - +35 mV)
• inactivated state; activation gate opened, inactivation gated closed; (+35 - -90 mV)

Question 3

What are the different configurations of the gate on a potassium channel and in what conditions do the states occur?

Answer 3

• resting state; gate closed; (-90 - +35 mV)

- slow activation; gate opened/opening; (+35 - -90 mV)

Question 4

How does the selectivity filter on a potassium channel work?

Answer 4

Hydrated ions are too large to pass through the channel.

Carbonyl oxygens are spaced so potassium ions my dehydrated but sodium ions are not dehydrated.

Question 5

What factors affect propagation speed of an action potential?

Answer 5

Mylination and fiber diameter; mylination and increased fiber diameter result in faster propagation speed