Membrane Potentials

Excitable Tissues and Resting Membrane Potential Prof. Vajira Weerasinghe Dept of Physiology Faculty of Medicine

Objectives ,[object Object],[object Object]

Excitable Tissues ,[object Object]

Excitable tissues excitable neuron muscle ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],Non-excitable Red cell GIT

Membrane potential ,[object Object],[object Object],[object Object]

Excitable tissues ,[object Object],excitable neuron muscle ,[object Object],Non-excitable Red cell GIT

Resting Membrane Potential ,[object Object],[object Object],[object Object],[object Object],[object Object]

Ionic distribution ,[object Object],[object Object],[object Object],[object Object],[object Object],K + Pr - Na + Cl -

Ionic distribution 103 4 Cl - 2.4 0 Ca 2+ 28 10 HCO 3 - 4 140 K + 142 10 Na + Extracellular Intracellular Ion

Gibbs Donnan Equilibrium ,[object Object],[object Object]

Flow of Potassium ,[object Object],[object Object],[object Object],K + K + K + K + K + K + K + K + K + K +

Flow of Potassium ,[object Object],K + K + K + K + K + K + K + K + K + K +

Nernst potential (Equilibrium potential) ,[object Object],[object Object]

Nernst potential (Equilibrium potential) ,[object Object],(mmol/l) 28 2.4 103 4 142 Extracellular -89 4 Cl - +129 0 Ca 2+ -23 10 HCO 3 - -92 140 K + +58 10 Na + Nernst potential Intracellular Ion

Goldman Equation ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Ionic channels ,[object Object],[object Object],[object Object],K + Na +

Na/K pump ,[object Object],[object Object],[object Object],3 Na + 2 K + ATP ADP

Factors contributing to RMP ,[object Object],[object Object],[object Object],[object Object],[object Object]

Action Potential (A.P.) ,[object Object],[object Object],[object Object],[object Object]

Depolarisation Repolarisation -90 +35 RMP Hyperpolarisation

Inside of the membrane is ,[object Object],[object Object],[object Object],[object Object],-90 +35

[object Object],[object Object],[object Object],-90 +35 Threshold level

[object Object],[object Object],[object Object],-90 +35

[object Object],[object Object],[object Object],[object Object],-90 +35 1 msec

[object Object],[object Object],[object Object],[object Object]

Physiological basis of AP ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Physiological basis of AP ,[object Object],[object Object],[object Object],[object Object],[object Object]

VOLTAGE-GATED ION CHANNELS ,[object Object],[object Object],[object Object],outside inside Activation gate Inactivation gate

[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],outside inside outside inside -90 Threshold level +35 Na+ Na+ Na+ m gate h gate outside inside

VOLTAGE-GATED K Channel ,[object Object],[object Object],outside inside

[object Object],[object Object],[object Object],[object Object],[object Object],outside inside outside inside -90 At +35 K+ K+ n gate

Refractory Period ,[object Object],[object Object],[object Object],-90 +35 outside inside

Refractory Period ,[object Object],[object Object],[object Object],[object Object],-90 +35 outside inside

Propagation of AP ,[object Object],[object Object],[object Object],[object Object]

Propagation of AP ,[object Object],[object Object],[object Object]

AP propagation along myelinated nerves ,[object Object],[object Object]

AP propagation along myelinated nerves ,[object Object],[object Object],[object Object]

[object Object],[object Object],[object Object],3 Na + 2 K + ATP ADP

Membrane stabilisers ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Muscle action potentials ,[object Object],[object Object],[object Object]

Skeletal muscle ,[object Object]

Cardiac muscle action potential ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],Duration is about 250 msec

Cardiac muscle action potential ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Smooth muscle ,[object Object],[object Object],[object Object],[object Object]

Membrane Potentials

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Membrane Potentials