RESTING MEMBRANE POTENTIAL & ACTION POTENTIAL MR. Arjun Maitra Assistant Professor Dept. of...
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Transcript of RESTING MEMBRANE POTENTIAL & ACTION POTENTIAL MR. Arjun Maitra Assistant Professor Dept. of...
RESTING MEMBRANE POTENTIAL&
ACTION POTENTIAL
MR. Arjun MaitraAssistant ProfessorDept. of PhysiologyPCMS&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 FORPREPARING THE CONTENTS. REMEMBERTHESE SLIDES ARE NOT THE SUBSTITUTE OF YOUR TEXT BOOKS
ANIMATIONS AND DIAGRAMS ARE COLLECTED FROM DIFFERENT WEBSITESOLELY FOR EDUCATION PURPOSE.
MEMBRANE POTENTIAL
Vm = Vin -- Vout
IONIC DISTRIBUTION
Ions Inside cell Outside cell EquilibriumPotential
Sodium 15.0 150.0 +55mV
Potassium 150.0 5.5 -75mV
Chloride 9.0 125.0 -69mV
OrganicAnions
385.0 ------- ------
Role of Ions
SODIUM Na
POTASSIUM K
CHLORIDE Cl
CALCIUM Ca
+
+
_
+ +
-
A
Resting Membrane Potential
Vr = Vin
[ Normal range -60mV ---- -70mV (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 SOLVERA simple GLIAL cell
Nernst Equation & Equilibrium Potential
• ELECTRICAL DRIVING FORCE = CHEMICAL DRIVING FORCE
EK = -75mV
(Nernst Potential)
Neurons are complicated as they have Resting channels
for
Different ion species
GOLDMAN’S EQUATION
A new approach to quantify the contribution of different ions
• Concentration gradient• Conductance/Permeability
PERMEABILITY RATIO (At Rest) PK : P Na : P Cl = 1.0: 0.04 : 0.45
(At peak of Action Potential) PK : P Na : P Cl = 1.0 : 20 : 0.45
ELECTRICAL EQUIVALENT CIRCUIT
Conductance = 1/ohm = 1 / g RUnit expressed as ‘S’ = Siemens
Ohm’s Law V=IR => I =V/R => I = gV
gNa= nNa X gNa
gK = nK X gK
gCl= nCl X gCl
INa I
K
Vr =
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”- 4th 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”- 4th Edn