Action Potential

Question 1

What is the resting potential of a neuron?

Answer 1

The difference in electrical charge between the inside of a neutron and the outside of a neutron

Question 1

When at rest, the cell membrane of a neuron maintains what kind of gradient?

Answer 1

An electrical gradient, also known as polarization

Question 2

What is a neuron’s membrane composed of?

Answer 2

2 layers of phospholipid molecules + embedded cylindrical proteins that allow certain chemicals to pass through

Question 3

What is polarization in a neuron’s membrane?

Answer 3

(AKA electrical gradient) the difference in electrical charge between the inside and outside of a cell

Question 4

The inside of a membrane has what kind of a charge?

Answer 4

The inside has a slight negative charge compared to the outside (due to negatively charged proteins)

Question 5

What is resting potential?

Answer 5

The difference in voltage between the inside and outside of a cell

Question 6

How do researchers measure the resting potential of a cell?

Answer 6

By inserting a microelectrode into the cell body

Question 7

What is the average electrical charge of the inside of a neuron?

Answer 7

-70 millivolts (mV)

Question 8

What is the concentration gradient?

Answer 8

The difference in distribution of ions across the cell membrane

Question 9

What are action potentials?

Answer 9

Messages sent by the axons

Question 10

When does hyperpolarization occur?

Answer 10

Increased polarization as a product of using an electrode to increase a membrane’s negative charge

Question 11

What does it mean to depolarize a neuron?

Answer 11

To reduce a neuron’s polarization to zero

Question 12

Any depolarization that reaches/passes the threshold of the membrane produces what?

Answer 12

Action potential

Question 13

What does the all-or-none law state?

Answer 13

The amplitude and velocity of an action potential are independent from the intensity of the stimulus that initiated it, as long as the stimulus reaches the threshold

Question 14

What are the 3 principles of the chemicals events behind action potential?

Answer 14

1. At the start, sodium ions are mostly outside the neuron, and potassium ions are mostly inside.
2. Depolarizing the membrane opens the sodium and potassium channels.
3. At the peak of the action potential, the sodium channels close.

Question 15

When do voltage-gated sodium and potassium channels typically open, and what happens to sodium channels at the peak of the action potential?

Answer 15

Voltage-gated sodium and potassium channels open when the membrane is depolarized, and sodium channels snap shut at the peak of the action potential

Question 16

What is the absolute refractory period?

Answer 16

The period of time after the peak of the action potential, in which the sodium channels shut tightly and remain tightly shut for approximately the next millisecond. During this time, the membrane cannot produce an action potential, regardless of the stimulation

Question 17

What is the relative refractory period?

Answer 17

After the absolute refractory period, sodium channels relax a bit, while the rapid departure of potassium ions has driven the membrane potential farther into negative territory than usual, and a stronger-than-usual stimulus is necessary to initiate an action potential. (2-4 ms)

Question 18

What are the 2 variables that the refractory period depends on?

Answer 18

Closed sodium channels and potassium flowing out of the cell

Question 19

Suppose researchers find that Axon A can produce up to 1,000 action potentials per second (at least briefly, with maximum stimulation), but Axon B can never produce more than 100 per second (regardless of the strength of the stimulus). What could we conclude about the refractory periods of the two axons?

Answer 19

Axon A has a shorter refractory period than Axon B and can recover more quickly to fire more action potentials