RESTING MEMBRANE POTENTIAL & ACTION POTENTIAL MR. Arjun Maitra Assistant Professor Dept. of Physiology PCMS&RC

TO MY STUDENTS HERE I HAVE TRIED TO SIMPLIFY THE HUGE SUBJECT WITH ANIMATIONS, DIAGRAMS, FLOW CHARTS & RELEVENT MCQs. DIFFERENT TEXT BOOKS AND REFERENCE BOOKS HAVE BEEN USED FOR PREPARING THE CONTENTS. SLIDES ARE NOT THE SUBSTITUTE REMEMBERTHESE SLIDES ARE NOT THE SUBSTITUTE OF YOUR TEXT BOOKS ANIMATIONS AND DIAGRAMS ARE COLLECTED FROM DIFFERENT WEBSITE SOLELY FOR EDUCATION PURPOSE.

MEMBRANE POTENTIAL V m = V in -- V out

IONIC DISTRIBUTION IonsInside cellOutside cellEquilibrium Potential Sodium mV Potassium mV Chloride mV Organic Anions

Role of Ions SODIUM Na POTASSIUM K CHLORIDE Cl CALCIUM Ca + + _ + - A

Resting Membrane Potential V r = V in [ Normal range -60mV mV (Neurons)] + Na + K No ionic movement across the cell membrane

1.How do ionic gradient contribute to RMP 2.How are they maintained 3.What prevents the ionic gradients from dissipating by diffusion of ions across the membrane through passive channels

PUZZLE SOLVER A simple GLIAL cell

Nernst Equation & Equilibrium Potential ELECTRICAL DRIVING FORCE = CHEMICAL DRIVING FORCE E K = -75mV (Nernst Potential)

Neurons are complicated as they have Resting channels for Different ion species

GOLDMANS EQUATION A new approach to quantify the contribution of different ions Concentration gradient Conductance/Permeability PERMEABILITY RATIO (At Rest) P K : P Na : P Cl = 1.0: 0.04 : 0.45 (At peak of Action Potential) P K : P Na : P Cl = 1.0 : 20 : 0.45

ELECTRICAL EQUIVALENT CIRCUIT Conductance = 1 / ohm R Unit expressed as S = Siemens Ohms Law V=IR => I =V/R => I = V g Na= n Na X a g K = n K X g Cl= n Cl X Cl

I Na I K V r =

Role of Na – K ATPase in maintenance of Resting Membrane Potential + + A Positive Controversy Na – K ATPase +

ACTION POTENTIAL

Channels associated to Action potential VDSC – Voltage gated sodium channel VDKC – Voltage gated potassium channel A type- Fast Slow type Inward Rectifier

IONIC MOVEMENT DURING ACTION POTENTIAL

Voltage Gated Sodium Channel

Voltage Gated Potassium Channel Inward Rectifier Channel Voltage Gated Fast Voltage gated Slow

REFERENCES A.G.Brown – Nerve Cells & Nerve Tissue- 4 th Edn. Carpentar – Neurophysiology Kandle & Schwartz – Principles of Neural Sciences Longstaff.A – Instant notes on Neurosciences W. Ganong – Review of Medical Physiology 2005 Corriteli – Biophysics 2003 Devlyn – Biochemistry- 4 th Edn