This document discusses the resting membrane potential of neurons. It begins by introducing the concept of resting membrane potential and its importance for cell-to-cell communication. It then explains that the resting membrane potential of neurons is approximately -90 mV due to three main factors: 1) the diffusion potential of potassium ions across the membrane, which makes the inside more negative; 2) sodium ion diffusion through leak channels; and 3) the active transport of sodium and potassium ions via sodium-potassium pumps, which pumps more positive charges out of the neuron. The Nernst and Goldman equations are used to calculate these diffusion potentials.

1. RESTING MEMBRANE
POTENTIAL

2. CONTENTS
• INTRODUCTION
• BASIC PHYSICS OF MEMBRANE POTENTIAL
1. MEMBRANE POTENTIAL CAUSED BY ION CONCENTRATION
2. THE NERNST EQUATION
3. THE GOLDMAN EQUATION
• RESTING MEMBRANE POTENTIAL OF NEURON
• ACTIVE TRANSPORT OF Na+ & K+ ION THROUGH THE MEMBRANE
• ORIGIN OF NORMAL RESTING MEMBRANE POTENTIAL
• MEASURING THE MEMBRANE POTENTIAL

3. INTRODUCTION
•The potential difference across the membrane of a cell
at resting state is called Resting Membrane Potential
•The relatively stable membrane potential of a cell in a
unstimulated state.
•It plays important role in cell to cell communication.
•Some cells such as nerve cells and muscle cells rapidly
changing electrochemical impulses which are used to
transmit signals.

4. BASIC PHYSICS OF MEMBRANE
POTENTIALS
1. MEMBRANE POTENTIAL CAUSED BY ION
CONCENTRATION :
•Due to K+ ion , the potential difference inside nerve
fiber membrane is -94 mV.
•Due to Na+ ion , the potential difference inside nerve
fiber membrane is +61 mV.

6. 2. THE NERNST EQUATION:
•The Nernst Equation describes the relation of Diffusion
Potential to the Ion Concentration across a membrane.
•The diffusion potential level across a membrane that
exactly opposes the net diffusion of a particular ion is
called Nernst Potential.
•The magnitude of Nernst Potential is determined by the
ratio of the conc. of specific ion on the both sides of
membrane.
•The greater the ratio, the greater is the tendency of ion to

7. CALCULATION OF NERNST
POTENTIAL
1. AT THE NORMAL BODY TEMPERATURE 98.6 F:
EMF(millivolts)= + 61 log concentration inside
Z concentration outside
2. AT ANY TEMPERATURE:
EMF(millivolts)= + 2.303 RT log concentration inside
Z F concentration outside

8. 3. THE GOLDMAN EQUATION:
•The Goldman Equation is used to calculate the diffusion
potential when the membrane is permeable to several
different ions.
•When membrane is permeable to different ions then
diffusion potential depends on three factors:
1. Polarity of electrical charge on each ions.
2. The permeability of the membrane (P) to each ions
3. Concentration(C) of the respective ions

9. •Evident from Goldman Equation:
1.Na+,K+ and Cl- ions are most important ions for development
membrane potentials.
2. Quantitative importance of each of ions in determining voltage is
proportional to membrane permeability for that particular ions.
Calculation of Goldman Equation:
EMF(millivolts)= - 61 log C(Na+i)PNa + C(K+i)PK + C(Cl-i)PCl-
C(Na+o)PNa + C(K+o)PK + C(Cl-o)PCl-

10. RESTING MEMBRANE POTENTIAL
OF NEURONS
•The Resting Membrane Potential of large nerve fibers is
about
-90 mV.
•The Potential inside the fiber is 90 mV more negative than
the potential in the extracellular fluid on outside of fiber.
Active Transport of Na+ and K+ ions through the
membrane : The Sodium-Potassium Pump
• All cell membrane of the body have a powerful Na+ -K+

11. • It transports 3 Na+ ions outside of the cell and 2 K+ ions to the inside.
• It is also called Electrogenic Pump as it pumps more positive charges
outside the cell than inside . Thus creating negative potential inside a
cell.
• The Na+ - K+ pump also causes large concentration gradients for Na+
and K+ :
Na+(outside):142mEq/L K+(outside):4 mEq/L
Na+(inside) :14mEq/L K+(inside): 140mEq/L
The ratios of these two respective ions from inside to outside :
Na+(inside) =0.1 K+(inside) =35.0

13. ORIGIN OF NORMAL RESTING
MEMBRANE POTENTIAL
Contribution of the Potassium Diffusion Potential
•There is only movement of K+ ion by the open channels inside
and outside the membrane.
•By using Nernst Equation :
Resting Potential inside the fiber would be equal to -94 mV.

14. CONTRIBUTION OF SODIUM DIFFUSION THROUGH
NERVE MEMBRANE:
•Addition permeability of nerve membrane to Na+ ion caused
by K+-Na+ leak channels.
•The ratio of Sodium ions from inside to outside the membrane
is 0.1 which gives calculated Nernst potential for the inside of
membrane is +61 mV.
•The Nernst potential for potassium diffusion -94 mV.
•Since the membrane is permeable to both Na+ and K+ ion so
we use Goldman Equation.
•Goldman equation gives a potential inside the membrane of -

15. CONTRIBUTION OF NA+ - K+ PUMP
• Na+ K+ Pump provide an additional contribution to resting
potential.
•There is continuous pumping of three Na+ ions outside and
two K+ ions inside the membrane.
•The pumping of sodium ions to outside and potassium ions to
inside causes continual loss of positive charges from inside
the membranes thus creating an additional degree of
negativity.
• The net membrane potential when all these factors are

17. BIBLIOGRAPHY
• GUYTON AND HALL- THE TEXTBOOK OF
PHYSIOLOGY
• GANONG’S REVIEW OF MEDICAL PHYSIOLOGY
• DR.A.K JAIN OF MEDICAL PHYSIOLOGY

18. THANK YOU