MP+AP

Question 1

What is the typical range of a resting membrane potential?

Answer 1

-5 to -100mV

Question 2

How is resting mebrane potential measured?

Answer 2

Measured electrophysiologically by comparing the cell potential to a reference (external)

Question 3

Net movement of charges =

Answer 3

electrical current (I)

Question 4

All currents in a cell are carried by…

Answer 4

ions

Question 5

What are the conditions for a cell to have a membrane potential?

Answer 5

• must be permeable to ions
• there must be a concentration gradient for an ion

Question 6

What ion determines RMP for a neuron?

Answer 6

K⁺

Question 7

The concentration gradient for a neuron (K⁺) favours diffusion ______ the cell.

Answer 7

out of

Question 8

The electrical potential is when…

Answer 8

the concentration force drawing the K⁺ out of the cell balanced by electrical force holding it in.

Question 9

What does the Nernst equation quantify?

Answer 9

The equilibrium potential for an ion

Question 10

What is the Nernst equation? What are the variables?

Answer 10

R = thermydynamic gas constant (8.314 J/mol*K)

Z = valence of the ion

F = Faraday’s constant (9.65x10⁴ C/mol)

Question 11

Modification of the Nernst equation allows the calculation of RMP based on concentration and permeabilities of all relevant ions, giving what equation?

Answer 11

Goldman-Hodgkin-Katz equation (aka the constant field equation)

Question 12

What are the characteristics and functions of the Na⁺/K⁺ ATPase pump?

Answer 12

Moves 3Na⁺out and 2K⁺ in

Electrogenic

Hyperpolarizes the cell

Requires an ATP molecule for each cycle, RMP requires energy for maintenance

Question 13

Who developed the voltage clamp technique to address the question of hor depolarization precisely affects the permeability of ions?

Answer 13

Hodgkin and Huxley

Question 14

The apparatus involved in the voltage clamp technique was used on what kind of axon and what did it manipulate?

Answer 14

A giant squid axon, the size of the axon allowed researchrs to plave electrodes in the axon and manipulate voltage and current.

Question 15

When Hodgkin and Huxley manipulated the salinity of the extracellular solution by decreasing the [Na⁺], what was observed? What did this suggest?

Answer 15

They found that the peak of the action potential for smaller. This suggested that the flow of Na⁺ ions is incolved in the peak of the action potential.

Question 16

When Hodgkin and Huxley manipulated the voltage to meausure the current, what did they find?

Answer 16

When the hyperpolarized the cell they saw virtually no current, only a capacitive transient. When they depolarized the cell they saw large inward and outward currents.

Question 17

What were Hodgkin and Huxley’s major findings about the permeability of ions and the action potential?

Answer 17

Action potentials do indeed change the permeability of certain ions. As the action potential rised, so does the permeability of Na⁺ ions. This same relationship is seen with K⁺ ions; however, the increase is of a lower magnitude and the increase is delayed and persists longer than that of Na⁺

Question 18

What two toxins can block voltage gated Na⁺ channels?

Answer 18

Tetrodotoxin (TTX) and saxitoxin (STX)

Question 19

During RMP, Na⁺ and K⁺ are open/closed.

Answer 19

open/closed - however K⁺ is moving through leak channels.

Question 20

Does K⁺ or Na⁺ have higher permeability during RMP?

Answer 20

K⁺

Question 21

During depolarization what is the movement of Na⁺ and K⁺ ions?

Answer 21

Question 22

During repolarization, what is the movement of ions?

Answer 22

The Na⁺ channel is inactivates (“ball and chain”) blocking any Na⁺ movement, K⁺channel opens allowing K⁺ to rush out of the cell.

Question 23

Define absolute refractory period.

Answer 23

Cell is incapable of generating a new AP

Question 24

Define relative refractory period.

Answer 24

More difficult to generate a new AP

Question 25

TImmediately following an action potential, why is the threshold for initiation higher than usual?

Answer 25

The relative refractory period.

Question 26

During which type of refractory period is there no Na⁺ conductance?

Answer 26

Absolute

Question 27

Do individual action potentials travel along the axon?

Answer 27

No, an AP at one location will lead to the depolarization at adjecent areas of the axon. (Propagation)