the resting membrane potential

Question 1

what is the membrane potential

Answer 1

the electrical charge that exits across a membrane and is always expressed as the potential inside the cell relative to the extracellular solution.

Question 2

how is resting potential measured

Answer 2

use a fine glad micropipette that serves as a micro electrode
this is filled with a conducting solution and can penetrate the cell membrane
the conducting solution will allow the tiny flow of current to be measured electronically by connecting to a voltmeter.
voltmeter is connected to a reference or ground electrode

Question 3

range of animal cell resting membrane potential

Answer 3

-20 to -90mV

Question 4

cardiac myocyte membrane potential

Answer 4

-80mV

Question 5

neurone membrane potential

Answer 5

-70mV

Question 6

skeletal muscle myocyte membrane potential

Answer 6

-90mV

Question 7

smooth muscle myocyte membrane potential

Answer 7

-50mV

Question 8

how is the resting potential set up

Answer 8

open K+ channels dominate the membrane ionic permeability at rest
there is a chemical gradient for K+ and a electrical gradient too.
when these are equal and opposite there will be no net movement if Ka + but there will be a negative membrane potential.
therefore the resting membrane potential arises because the membrane is selectively permeable to K+.
the greater the membrane potential difference the more the efflux of K+ will be resisted by being drawn back by the -ve charge inside the cell.

Question 9

what is the Nernst equation used for

Answer 9

allows you to calculate the membrane potential at which K+ will be in equilibrium given the extracellular and intracellular K +.
if a membrane is selectively permeable to K + alone its membrane potential will be at Ek .