Chapter 7

Question 1

Contrast a graded response with an action potential.

Answer 1

Graded response is proportional to stimulus intensity and is degraded over a distance. Action potential is all or none once a depolarization surpasses threshold.

Question 2

What are the Na+ and K+ currents dependent on?

Answer 2

Time and Voltage dependent

Question 3

How does a macroscopic current become generated?

Answer 3

Through the summation of many single ion channels that generate current when ions enter or leave the cell

Question 4

What is beneficial about the Hodgkin-Huxley model?

Answer 4

Predicts macroscopic currents and the shape of the action potential

Question 5

What generates the rapid depolarization phase of an action potential?

Answer 5

Opening of Na+ channels that allows Na+ ions to enter the axon/cell.

Question 6

How can you block the Na+ channels (voltage-dependent)?

Answer 6

Neurotoxins or anesthetics

Question 7

Can Ca2+ participate in action potentials?

Answer 7

Yes, it is an ion with a positive charge! So it functions in electrical and chemical coupling mechanisms. Responsible for action potentials in cardiomyocytes.

Question 8

What are the different types of Ca2+ channels? (5)

Answer 8

L-type, T-type, P/Q-type, N-type, and R-type

Question 9

How are the different types of Ca2+ channels characterized?

Answer 9

Through their kinetic properties and their sensitivity to inhibitors

Question 10

What determines the resting potential?

Answer 10

K+ channels

Question 11

What else do K+ channels participate in besides the resting membrane potential?

Answer 11

The frequence of action potentials and their termination (refractory phase)

Question 12

What is the Kv family of K+ channels responsible for?

Answer 12

The delayed outward rectifying current as well as the transient A-type current

Question 13

What are the Kir K+ channels responsible for?

Answer 13

They mediate inward rectifying K+ currents

Question 14

What are K2P channels responsible for?

Answer 14

Detecting stress

Question 15

What participates in the propagation of electrical signals in neurons?

Answer 15

Local current loops

Question 16

Why are axons wrapped in myelin?

Answer 16

To improve the efficiency and speed to which an electrical current can propagate through the axon.

Question 17

What determines the velocity of an electrical signal?

Answer 17

The cable properties of the membrane and cytoplasm of the cell

Question 18

Which part of the action potential is called the “overshoot”?

Answer 18

The part that is above 0 mV

Question 19

Can the shape of an action potential be changed in some cells?

Answer 19

Yes, by hormonal modulation

Question 20

What is the time constant of a depolarization equal to?

Answer 20

t = RC

t = time constant

R = Resistance

C = Capacitance

Question 21

What is electrotonic conduction?

Answer 21

The decay that is seen with a depolarization/hyperpolarization that degrades over a distance from the stimulus site. (Graded potentials only).

Question 22

Does the action potential propogate at constant velocity or is there an acceleration/deceleration? What is a direct result of this?

Answer 22

Constant velocity. This causes the time delay between the stimulus and the peak of the action potential to increase linearly with distance from the stimulus site.

Question 23

What 2 variables are responsible for excitation and how are they related to each other?

Answer 23

Duration of stimulus and stimulus intensity. The larger the product of the two variables, the more likely you will get excitation (they are inversely related).

Question 24

TEA blocks?

Answer 24

Potassium channels

Question 25

TTX blocks?

Answer 25

Sodium channels