Resting membrane Potential by Dr. Pandian M.pptx

RMP this ppt for MBBS, Medical, Pre and Para, Allied Health Science, Physiotherapy, Nursing, BDS, DMLT, MLT, and etc. only study purposes

1. Resting membrane Potential (RMP) Dr. Pandian M. Assistant Professor Dept. of Physiology

2. Nobel prize 1920 (1864 – 1941) Walther Hermann Nernst

3. What is a resting membrane potential? How is it recorded?

4. Definition Electrical potential existing across the cell membrane under resting state is called resting membrane potential . It indicates the resting state or state of polarization of the cell membrane

5. One microelectrode is placed into the interior of the cell and another is placed outside the cell in interstitial fluid. These electrodes are connected to appropriate voltmeter for recording resting membrane potential. It varies from –65 to –90 mV ( with negativity inside the cell) in different cells.

6. Genesis of RMP The number of cations is matched with number of anions in ICF and ECF and electro neutrality is maintained. But across the cell membrane at rest there is no electro neutrality . Outside the cell membrane the cations are in excess and inside the cell membrane the anions are in excess.

7. ESTING MEMBRANE POTENTIAL (R.M.P.) Definition: It is the difference in electrical potential (voltage) between the inside & the outside membrane surfaces under resting conditions, The inside is negative relative to the outside of the membrane (polarized state) In large nerve fibers & large skeletal muscles is -90mV. In medium-sized neurons is -70 mV. In non excitable cells (RBC's & epithelial cells) is -20 to-10 mV. The RMP is (-) means the inside is - ve in relation to outside.

8. Resting Vm for various cell types Cell types Skeletal muscle fibers Smooth muscle fibers Astrocytes Neurons Erythrocytes Photoreceptor cells Resting potential -85 to 95 mV -50 to -60 mV -80 to -90 mV -60 to -70 mV -8 to -12 mV -40 mV (dark) to -70 mV (light)

9. Causes of R.M.P. T he unequal distribution of ions on both sides of membrane is due to: (1) Selective permeability of the membrane (for Na + & K + ). (2) Na + ⁃ K + pump.

10. 1. S elective permeability of the membrane K + , Proteins, PO 4 -3 : are mainly inside the membrane (very great inside the nerve cell). Na +, CI - , HCO 3 - : are mainly outside the membrane (very great outside the nerve cell).

11. At rest - The membrane is permeable to intracellular K + through (inward rectifier K + channels). amount of K + outflow is > amount of Na + inflow 20 to 100 times. The membrane is impermeable to intracellular proteins, organic anions. So - accumulation of more (+ ve ) ions on the outside of the membrane & more (- ve ) ions on the inside of the membrane. Each ion tries to reach an equilibrium potential: i.e. the flow of ion in one direction (by conc. gradient) is balanced by the flow in the opposite direction (by electrical gradient).

12. 2. Na + - K + Pump Na + is actively transported to the outside of the cell (against conc. & electrical gradients) K + is actively transported to the inside of the cell (against conc. gradient) Na + - K + pump (moves 3 Na + ions to outside for each 2 K + ions to inside) through a carrier protein with ATPase activity (using energy from ATP hydrolysis)

13. So (+ ve ) charges pumped to the outside > to the inside. The net is decrease of (+ ve ) ions on the inside. So Na + - K + pump is electrogenic (helps to keep the membrane potential),.

14. Na + - K + Pump

15. Na + - K + Pump Figure 5-4

16. Role of Na+ ­ K+ pump . It pumps three Na + outside and two K + inside each cycle. Thus there is net loss of one positive charge with each cycle. This pump is responsible for creating potential gradient across the cell membrane.

17. Role of Gibbs Donnan effect. Role of potassium diffusion channels. Role of Sodium potassium leaky channels. Role of Sodium potassium pump.

18. Summary: Resting Membrane Potential

19. Factors affecting diffusion A. Solubility of substance in the Lipid bilayer. B. Its molecular weight and size. C. Charges on the particle. D. Concentration gradient across the cell membrane. E. Area of the membrane. F. Thickness of the membrane. G. Charges at the pore H. Temperature I. Electrical gradient and pressure gradient across the cell membrane

20. Maintenance of RMP Presence of K leaky channels Voltage gated k diffusion channels Contribution of Na + -­ K + pump

21. Referred :- Text book of Medical Physiology Guyton, 14 th edition, Text book of Medical Physiology Indu khurana , Text book of Medical Physiology Vander’s Text book of Medical Physiology Sembulingam & LPR

22. THANK YOU . . .