The Membrane Potential

Question 1

Nernst Equation

Answer 1

Eion = k(ln[ion]outside - ln[ion]inside)
or Eion = RT/(zF)ln([ion]outside/[ion]inside)
Eion = 58mV/zlog([ion]outside/[ion]inside)

(The equilibrium potential of an ion is equal to the gas constant times absolute temperature divided by the valence of the ion in question (z) and the Faraday constant times the natural logarithm of the concentration of ions on the outside divided by the concentration of ions on the inside)

Question 2

Coulomb

Answer 2

the measure of electrical charge of a particle

The quantity of charge transported in one second by a current of one ampere

Question 3

Charge of a proton

Answer 3

1.6x10^-19 C

Question 4

Avogrado’s number

Answer 4

6.022x10^23

Number of molecules in one mole of any substance

Question 5

Faraday constant

Answer 5

The total charge on a mole of any monovalent ion

Question 6

Potential differences in cells are always expressed in terms of the ___ of a cell relative to the ___.

Answer 6

inside, outside

Question 7

R =

Answer 7

E (Potential difference/voltage(work)) / I (Current or net flow of charge)

Question 8

Conductance

Answer 8

Reciprocal of resistance

Question 9

High salt concentrations are (outside/inside) of the cell

Answer 9

inside

Question 10

(T/F) The ions on one side cannot interact electrostatically with ions on the other side because the membrane is too thick.

Answer 10

False

Question 11

The net ____ (+/-) charge on a cell is distributed evenly throughout the cell. (True or false)

Answer 11

negative (-),

false

Question 12

The rate of flow of an ion across the plasma membrane is determined by

Answer 12

The concentration gradient (the difference in the concentrations of the ion on the two sides of the membrane)

The voltage difference across the plasma membrane

The conductance of the ion channels (the ease with which ions move through the ion channels across the membrane).

Question 13

RT/F at room temperature

Answer 13

58mV

Question 14

RT/F at 37 degree celsius

Answer 14

61mV

Question 15

Donnan equilibrium

Answer 15

The product of the concentration of potassium and chloride ions outside the cell is equal to the product of the concentration of potassium and chloride ions inside the cell (at electrochemical equilibrium, the equilibrium potential for potassium and chloride is equal)

Question 16

The neuron cell membrane is permeable to (2 ions)

Answer 16

potassium and chloride

Question 17

Sodium is more concentrated on the ____ of the cell and potassium is more concentrated on the ____ of the cell.

Answer 17

outside,

inside

Question 18

Sodium potassium pump

Answer 18

3 Sodium and 1 ATP bind to the inside of the protein and the sodium leaves the pump, and 2 potassium ions are pumped in

Question 19

Goldman equation

Answer 19

Em = 58mV*log( (pK[K+]outside+pNa[Na+]outside+pCl[Cl-]inside) / (pK[K+]inside+pNa[Na+]inside+pCl[Cl-]outside)

Simplified to Em = 58mV*log( ([K+]outside+b[Na+]outside) / ([K+]inside + b[Na+]inside) ), where b = the ratio of sodium to potassium permeability (0.02 in nerve cells) because in nerve cells, the contribution of chloride to the resting membrane potential is quite small

Question 20

Passive membrane properties

Answer 20

transmembrane resistance (resting),
axial resistance,
membrane capacitance

Question 21

Input resistance

Answer 21

Change in voltage over current

The specific membrane resistance divided by the membrane area

Question 22

The units of membrane resistance

Answer 22

ohm cm^2

Question 23

The specific membrane resistance is a function of ___.

Answer 23

the density of ion channels and their conductance

Question 24

Axial resistance is due to

Answer 24

intracellular fluid (it’s also known as longitudinal resistance)

Question 25

Length constant

Answer 25

lambda = the square root of membrane resistance/axial resistance

Defined as the distance over which and electronic potential decrements to 37% of its original peak value

Question 26

Membrane voltage at any point on the membrane

Answer 26

Vx = V0*e^(-x/lambda)

Question 27

There are higher concentrations of voltage dependent sodium channels at the ____ and input there will be especially effective.

Answer 27

axon hillock

Question 28

_____ is responsible for the gradual buildup and decline of potentials.

Answer 28

Capacitance (specifically membrane)

Question 29

Membrane time constant

Answer 29

tau = the product of membrane capacitance and membrane resistance

time necessary for the electronic potential to decrement to 37% its original peak value.

Question 30

How to calculate the duration of the synaptic potential

Answer 30

V = Vmax*e^(-t/tau)