Resting membrane potential

Question 1

What is the resting membrane potential?

Answer 1

The potential difference (mv) between the inside and outside of a cell at rest

Question 2

What is the value of the resting membrane potential?

Answer 2

-30mv and -90mv always polarised

Question 3

What is the average RMP for a neurone?

Answer 3

~-70mv

Question 4

What is the average RMP for a skeletal muscle cell?

Answer 4

~-90mv

Question 5

What ion are cells most permeable to at rest?

Answer 5

Potassium

Question 6

What leads to potassium loss from a cell?

Answer 6

High concentration gradient within the cell, diffusion of K+ out down conc grad.

Question 7

What pulls potassium into the cell?

Answer 7

Loss of +ve charge from cell as K+ moves down its concentration gradient creates and electrical pull into the cell

Question 8

If membrane just permeable to potassium at what point is there no net flux?

Answer 8

Flux driven by chemical gradient = flux driven by electrical gradient
-90mv

Question 9

What is equilibrium potential for potassium?

Answer 9

-90mV

Question 10

What is equilibrium potential?

Answer 10

Potential at which flux driven by chemical = flux driven by electrical gradient

Question 11

What is ENa?

Answer 11

+58mV

Question 12

Why is Em closer to Ek?

Answer 12

Cell at rest more permeable to potassium

Question 13

What is meant by the Nernst equation?

Answer 13

Gives the ion equilibrium potential

Question 14

What are components of Nernst equation?

Answer 14

Gas constant
Temp
Farradays constant
Valency
Concentration of ion in and out of the cell

Question 15

What does Na+K+ Pump do?

Answer 15

Uses ATP hydrolysis to pump 3NA+ out and 2 K+ in

Question 16

Why is Na+K+ important?

Answer 16

Ion gradient created allows ion movement to establish membrane potential

Question 17

What is the downfall of Nernst in estimating a cells Em?

Answer 17

Does not take into consideration concentrations and permeability of other ions

Question 18

What equation is better at estimating Em than Nernst?

Answer 18

Goldmann-Hodgkin-Catz

Question 19

Describe kinetics relationship between Na+ concentration and Na+ efflux from pump

Answer 19

Sigmoidal

Question 20

What is the effect of increased extracellular K+?

Answer 20

Reduces outward gradient so Em less negative and membrane repolarised

Question 21

What is effect of more external Na+ on Em?

Answer 21

Increased diffusion into cell depolarisation

Question 22

What is the effect of increased Cl- extracellularly on Em?

Answer 22

Concentration gradient to drive Cl- into cell so hyperpolarise membrane

Question 23

What is meant by the valence of an ion (Z) in Nernst?

Answer 23

Ion charge

Cl-= -1
Na+=+1

Question 24

When and ion is in steady state what can be said about ratio of +ve to -ve ions on inside and outside of cell?

Answer 24

Equal numbers

Question 25

Raising the extracellular K+ concentration bathing a nerve cell would

Answer 25

Make Ek less negative (more positive)

Question 26

Reducing the extracellular concentration of Na+ ions would

Answer 26

Make ENa more negative (less positive)

Question 27

A doubling of the intracellular Na+ ion concentration will

Answer 27

Stimulate membrane ion transport by Na+/K+ ATPase proteins

Question 28

A change of extracellular K+ ion concentration to 2.0 mM will

Answer 28

Decrease membrane ion transport by Na+/K+ ATPase proteins.