3. Action Potentials

Question 1

What are action potentials?

Answer 1

Very brief, large depolarizations that travel for long distances throug ha neuron without losing strength. Their function is rapid signaling over long distances.

Question 2

What does a suprathreshold do?

Answer 2

It is a stimulus that cuases an action potential.

Question 3

What are the two types of gated ion channels that action potentials require?

Answer 3

Voltage - gated Na+ channel and voltage - gated K+ channel. In addition, leak channels hep set the resting membrane potential.

Question 4

What are Na+ channels and K+ channels of axons activated by?

Answer 4

cell depolarization

Question 5

What are the steps to depolarization in a cell?

Answer 5

1) Na+ channel activation
2) Large Fna+
3) Na+ influx into cell causes depolarization.
This leads to a positive feedback in which more sodium channels activate

Question 6

What are the steps to repolarization in a cell?

Answer 6

1) Sodium channel inactivation. This is time dependent and usually occur very fast.
2) Potassium channel activation.

Question 7

What is Hyperpolarization?

Answer 7

Excess potassium current. Happens because some channels are still opened.

Question 8

During the absolute refractory period, no stimulus can trigger another action potential. Sodium channel is inactivated.

Answer 8

During the absolute refractory period, no stimulus can trigger another action potential. Sodium channel is inactivated.

Question 9

During the relative refractory period, only a larger-then-normal stimulus can initiate a new action potential.

Answer 9

During the relative refractory period, only a larger-then-normal stimulus can initiate a new action potential.