Download to read offline
![Sodium
potassium
pump
NA-K pump is a protein that has been
identified in many cells that maintains
the internal concentration
of potassium ions [K+] higher than that in
the surrounding medium (blood, body
fluid, water)
&
Maintains the internal concentration
of sodium ions [Na+] lower than that of
the surrounding medium.
It is an enzyme that uses metabolic energy
to transport (pump) Na+ outward and
K+ inward.
The Resting membrane potential of cells
and related bioelectric phenomena such as
the action potential depend on the steady
state difference in concentrations of
Na+ and K+ maintained by the pump.](https://image.slidesharecdn.com/2-230926070140-cf0f4899/85/2-BIOPHYSICS-Membrane-Potentials-and-Action-Potential-pptx-11-320.jpg)
Uploaded byDr Gaurav Saxena
2. BIOPHYSICS – Membrane Potentials and Action Potential.pptx
This document provides an overview of membrane potential and action potential, explaining concepts such as resting membrane potential, the role of the sodium-potassium pump, and the Nernst and Goldman equations. It details the factors influencing resting membrane potential, including ion concentration gradients and membrane permeability, as well as the dynamics of action potential. The document emphasizes the variability of resting membrane potential across different cell types and the need for individual ion considerations in calculations.
More Related Content
Similar to 2. BIOPHYSICS – Membrane Potentials and Action Potential.pptx
2. BIOPHYSICS – Membrane Potentials and Action Potential.pptx
- 1. BIOPHYSICS – ELECTROPHYSIOLOGY Membrane Potential& Action Potential Department of Physiotherapy M.L.B Paramedical Training College Jhansi Dr Gaurav Saxena Senior Teaching Faculty ( Assoc. Prof. ) & Head of Department
- 2.
- 3.
- 4. Introduction Any biologicalcell consist of various ions These ions are located either inside or outside the cell membrane Intra cellular matrix – Inside the cell Extra cellular Matrix- Out side the cell This concentration of ions in ECM or ICM is not equal, this difference in concentration of ion and charge generate a electrical potential known as Membrane potential Also known as – Transmembrane potential Membrane potential which is resulted from equilibrium in diffusion of all ions is known as Resting membrane potential
- 5.
- 6.
- 7. There arethree main elements of Resting membrane potential Concentration difference of ions Charge difference of ions Cell wall permeability Main factor that causes membrane potential is “diffusion”
- 8.
- 9.
- 10.
- 11. Sodium potassium pump NA-K pumpis a protein that has been identified in many cells that maintains the internal concentration of potassium ions [K+] higher than that in the surrounding medium (blood, body fluid, water) & Maintains the internal concentration of sodium ions [Na+] lower than that of the surrounding medium. It is an enzyme that uses metabolic energy to transport (pump) Na+ outward and K+ inward. The Resting membrane potential of cells and related bioelectric phenomena such as the action potential depend on the steady state difference in concentrations of Na+ and K+ maintained by the pump.
- 12. NA- K pumpuses ATP to move 3 sodium ion out and 02 potassium ions in continuously to maintain the concentration gradient for potassium and sodium
- 13. Movement of a ion Ex.Potassium K+ has a concentration of 150mm/l inside the cell and 5 mm/l outside the cell Due to high difference between ICM and ECM concentration of K +, a concentration gradient is created, which pushes K+ outside the cell However NA-K pump can efflux only limited K+ hence significant amount of K + moves out of cell through potassium leak channels or inward rectifier channels Using these channels concentration gradient pushes significant K+ out of the cell This lead to negative charge inside the cell and positive charge outside the cell , this process continues until there is a significant difference between inside and outside of the cell polarity This significant difference in polarity creates electrostatic gradient
- 15. Movement of Potassium Electrostaticgradient An electric charge generated due to difference between negative charge ( inside) and Positive charge ( outside) it pushes K+ from outside of the cell to inside It does not interfere the concentration gradient
- 16.
- 17. Introduction The exact point(value) when efflux of an ion ( due to concentration gradient ) is equal to influx of the same ion ( due to electrostatic gradient) is called the equilibrium potential or NERNST Potential For Potassium equilibrium potential or NERNST Potential is -92mv • In other word we need a -92mv potential to attract the quantity of potassium ion back in to the cell that is needed to balance the concentration gradient that is pushing K+ out of the cell
- 18. NERNST Potential of anION Concentration Gradient Cell Membrane permeability for that ion
- 19. So if acell have only one ION NERNST Potential Influx =efflux Resting Membrane Potential of a Cell
- 20. NERNST EQUATION But inreality a cell has multiple ions with different ICM and ECM concentration They ae permeable across the membrane Each has its own Equilibrium potential/NERNST potential Hence formulae for Resting Membrane potential should be based up on the NERNST potential of individual ion This formulae is known as NERNST equation
- 21. 04 mainions which affects the Resting Membrane potential are NA, K, Ca, Cl NERNST Equation for these ions are
- 23. Calculation of Resting Membrane Potential AsNernst potential of each ion is different hence , actual Resting membrane potential my be somewhere in between these individual Nernst potential or various ions But its mainly depends up on the Nernst potential of K+ , as K + is the most moving ion of the cell ( 90% of all ion movements) Movement of remaining all ions is less than 10 % , second most movement is of Cl - that is 08 % , Ca++ & Na + is 01 % So calculation of actual Resting Membrane potential depends up on the proportion of individual ion movement ( out of total ion movement) To calculate actual Resting Membrane Potential we need to multiple the individual movement proportion of each ion to its Nernst potential then add up the total Resting Membrane potential ( RMP)= ∑Nernst potential of individual ion X ion movement proportion
- 24. Movement proportion of various ions multipliedto its NERNST potentials
- 25. Generally innon excited state, the Resting Membrane potential of a Cell is 86mV to -90mV Its is always closest to the Ion which has the maximum permeability across the cell membrane Cell Resting membrane potential is highly depends up to the individual primality of an ion across the membrane If a cell changes its permeability , that will lead to change in the movement proportion of various ions and ultimately will lead to change in the Resting membrane of the Cell. Hence Resting membrane potential varies cell to cell ( -20 to -100V) Neuron = -70mV Skeletal = -90mV Epithelial cell = -50mV Adipose = - 40 mV Resting Membrane Potential(RMP) indicated the potential when a cell is in non excited state
- 26.
- 27. When themembrane is permeable to several ions the Membrane equilibrium potential that develops depends on Polarity of each ion Membrane permeability Ionic concentration This is calculated using Goldman Equation/ Goldman-Hodgkin- Katz ( GHK) Equation Vm- Membrane potential R- Ideal Gas constant T- Temp F- Ferrady constant
- 28. Important consideration GHK doesnot include all the ion, it just consider the major one- Potassium, Sodium and Chloride Rest of the ions has either very low concentration or has a very low transmembrane permeability ; hence they are not used GHK equation Even calcium which is an important ion physiologically is left out of this equation as it has a very low intra cellular concentration It is known that permeability of a cell is variable, and can change for an ion , hence if permeability of an ion is increased , it should be used in GHK for the calculation of membrane potential and vice versa
- 29.
- 30. Under restingcondition a cell is polarized Inside of a cell is Negatively charged (ICM) Outside of a cell is positively charged (ECM) An action potential is a rapid sequence of changes in the voltage across a membrane
- 33.
- 34.
- 35.
- 36.
- 37.
- 39. All or None LawofAP
- 41.
- 42.
- 43.
- 44.
- 45.
- 46.