Action potential

Question 1

What is the definition of threshold?

Answer 1

Where I-Na= I-K

Question 2

Why are there 2 gates on the sodium channel? When do they open/close?

Answer 2

To control sodium intake properly.

Gate 1 opens when threshold is reached.
Gate 2 begins to close at threshold. Because of the delay, the gate isn’t closed until the apex of the action potential.

Question 3

When a cell is slowly brought to threshold, does an action potential occur?

Answer 3

No.

Inactivation gates on sodium channels swing closed before action potential can occur.

Also, potassium gates can open.

Question 4

If an axon is stimulated in 2 spots, how many action potentials arise?

Answer 4

4- there is no directionality to APs stimulated in an axon

Question 5

When two APs traveling in opposite directions collide, what happens?

Answer 5

Both APs stop because gates are in refractory period on either side.

Question 6

How does an anesthetic affect APs?

Answer 6

Anesthetic blocks Na channels.

Question 7

What are the 2 factors that affect conduction velocity?

Answer 7

Larger Diameter

Myelin

Question 8

What are the 4 advantages of big axons?

Answer 8

1. Fast CV
2. Low threshold
3. Higher safety factor
4. Myelin

Question 9

Which axon will have a faster CV? .9 micron unmyelinated or 1.1 micron unmyelinated?

Answer 9

.9

Question 10

Which axon will have a faster CV? .9 micron myelinated or 1.1 micron myelinated?

Answer 10

1.1 micron

Question 11

What causes faster conduction in myelinated axons?

Answer 11

Ions cant flow out of axon in myelinated sections, thus more current flows in the axon.

*capacitance decreases in myelinated sections meaning there are less (-) charges to be neutralized by sodium influx. This causes greater CV.

Question 12

Why do patients with MS have times where they improve health?

Answer 12

Sodium channels migrate to portions of the axon that have been affected by the disease.