Resting Membrane Potential

Question 1

Diffusion potential

Answer 1

Potential difference generated across the membrane because of a concentration difference of an ion

Question 2

Potential difference in a normal mammalian nerve fiber

Answer 2

It’s about 94mV with negativity inside the fiber

Question 3

What creates a membrane potential

Answer 3

Concentration difference of ions across a selectively permeable membrane under appropriate conditions.

Question 4

Nernst potential

Answer 4

The diffusion potential level across a membrane that exactly opposes the net diffusion of a particular ion through a membrane

Question 5

How is Nernst potential determined

Answer 5

By the ratio of concentrations of that specific ion on the outside and inside of the membrane using an equation called the Nernst equation. Greater the ratio greater is the tendency of ions to diffuse in one direction therefore greater Nernst potential required to prevent additional net diffusion.

Question 6

Nernst equation

Answer 6

Calculate the Nernst potential for any univalent on at the normal body temp of 98.6 °F
EMF= +_ 61/z xlog( conc. Inside /conc. Outside)
z-electric charge of the ion

Question 7

Nernst equation assumes that the potential in extracellular fluid remains at

Answer 7

0 potential.

Question 8

Sign of the potential is +ve when

Answer 8

The ion diffusing from inside to outside is a - ve ion.

Question 9

Sign of potential is - ve when

Answer 9

the ion diffusing from inside to outside is +ve

Question 10

When membrane is permeable to several ions, diffusion potential that develops depends on 3 factors:

Answer 10

1. Conc. Of the respective ions on the inside and outside of the membrane.
2. Permeability of the membrane to each ion
3. Polarity of the electrical charge of each ion

Question 11

Goldman equation

Answer 11

Or the Goldman - hodgkins-Katz equation gives the calculated membrane potential inside the three membrane when it is permeable to several different ions.

Question 12

How is membrane potential measured

Answer 12

A pipette filled with electrolyte solution is impaled through the cell membrane interior of the fiber. Another electrode called the “indifferent electrode” placed in the extracellular fluid, and the potential difference between the inside and outside is measured using a voltmeter. Rapid changes in the membrane potential during transmission of nerve impulse is recorded by an oscilloscope.

Question 13

Voltage change area at the cell membrane is called

Answer 13

Electrical dipole layer

Question 14

Normal resting potential inside the nerve fiber

Answer 14

Is - 90 mV

Question 15

Na+ - K+ pump

Answer 15

An electrogenic pump, pumping 3 Na+ ions outside for each 2 K+ ions inside leaving a net deficit of positive ions on the inside causing a negative potential inside the cell membrane

Question 16

Concentration gradient for sodium and potassium across the resting nerve membrane

Answer 16

Na+ (outside) : 142mEq/L
Na+ (inside) : 14mEq/L
K+ (outside) : 4mEq/L
K+ (inside) : 140mEq/L

Question 17

Ratios of sodium and potassium ions from the inside to the outside are

Answer 17

Na+ ratio = 0.1

K+ ratio= 35.0

Question 18

How does potassium leak into a resting cell

Answer 18

Through Channel Proteins called “tandem pore domain”, potassium channel or potassium leak channel.

Question 19

It’s only potassium we’re the factor causing resting potential the resting potential inside the fiber would be

Answer 19

-94mV

Question 20

If only sodium were a factor causing resting potential the resting potential would be

Answer 20

+61mV

Question 21

According to Goldman equation the potential inside the membrane is

Answer 21

86mV which is near the potassium potential

Question 22

How does Na+-K+ pump contribute to testing potential

Answer 22

The Continual kids of positive charges from the inside of the membrane creating an additional degree of negativity about, - 4mV

Question 23

What contributed to membrane potential 90mV

Answer 23

The diffusion potentials alone caused by potassium and sodium diffusion would give a membrane potential of about 86mV
In addition -4mV is then contributed by the membrane potential by the acting electrogenic

Question 24

Gibbs-donnan phenomenon

Answer 24

Inequitable distribution of diffusible one across the cell membrane because of the presence of non diffusible ions on one side. Many impermeant anions on the inside contribute to the negative charge inside the cell