Exam 1: Action Potentials

Question 1

Define cell polarization

Answer 1

A difference in electrical charge between the inside/outside of the cell

Question 2

When cells are polarized they are _____ at rest

Answer 2

Negative

Question 3

Define depolarization

Answer 3

To become less polar (or more positively charged); usually stimulated or turned on

Question 4

Define hyperpolarized

Answer 4

To become more polar (or more negatively charged)

Question 5

Define repolarization

Answer 5

To return to resting membrane potential from a depolarized state`

Question 6

Which ion comes into the cell during depolarization?

Answer 6

Sodium

Question 7

During depolarization which direction does the membrane potential go?

Answer 7

Towards the Nernst for Na (more positive)

Question 8

During repolarization which ion channels open even more?

Answer 8

Potassium channels

Question 9

Are sodium channels fast or slow?

Answer 9

Fast

Question 10

Are potassium channels fast or slow?

Answer 10

Slow

Question 11

How many gates do sodium and potassium channels each have?

Answer 11

Sodium = 2
Potassium = 1

Question 12

What are the two gates in sodium channels?

Answer 12

Activation gate = aka M gate
Inactivation gate = aka H gate

Question 13

T/F The activation gate is open when the cell is at rest

Answer 13

False; the activation gate is closed when the cell is at rest
If the gate was open while at rest, sodium would be coming into the cell when we don’t want it to

Question 14

When does the activation gate open?

Answer 14

When the cell depolarizes to the threshold potential

Question 15

Which drugs affect sodium channels at the site of action on the ECF side?

Answer 15

-caines
Ex: Lidocaine

Question 16

T/F The inactivation gate (in sodium channels) is closed when the cell is resting

Answer 16

False; it is open while resting

Question 17

After the activation gate opens what occurs?

Answer 17

Sodium quickly comes into the cell and then the inactivated gate closes quickly, leading to the activation gate also closing

Question 18

What would happen if we kept the inactivation gate open while closing the activation gate?

Answer 18

More sodium would come into the cell

Question 19

What must happen with the membrane for the inactivation gate to open again?

Answer 19

The membrane must repolarize

Question 20

How do we get a cell back to Vrm?

Answer 20

Open additional potassium channels to help “repolarize” the cell after we wind down an action potential