Resting membrane potential

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by Dr. Chethan H. A.

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Resting membrane potential:

Resting membrane potential DR. Chethan H. A.

PowerPoint Presentation:

Nerves, musckes , glandular cells, macrophages, and ciliated cells

Diffusion potential:

Diffusion potential

PowerPoint Presentation:

Uneven Distribution of Solutes Amongst Body Compartments Cell membranes prevent most solutes from diffusing amongst compartments. Solutes are molecules which dissolve in liquid. Active transport of solutes helps create and maintain differences in solute concentrations. The body is kept in a state of chemical disequilibrium . F5-28

Relation of the Diffusion Potential to the Concentration Difference-The Nernst Potential:

Relation of the Diffusion Potential to the Concentration Difference-The Nernst Potential

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Nerst Equation The equilibrium potential is calculated using the Nerst equation: (mV) R= gas constant (8.314 jules/ o K.mol) T= temperature ( o K) F= Faraday constant (96, 000 coulombs/mol) z= the electric charge on the ion [I] out = ion concentration outside the cell [I] in = ion concentration inside the cell Derived under resting membrane conditions when the work required to move an ion across the membrane (up its concentration gradient) equals the electrical work required to move an ion against a voltage gradient.

Calculation of the Diffusion Potential When the Membrane Is Permeable to Several Different Ions :

Calculation of the Diffusion Potential When the Membrane Is Permeable to Several Different Ions

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Goldman Equation It is used to calculate the membrane potential resulting from all the participating ions when V m is not changing: P X = the relative permeability of the membrane to ion X (measured in cm/s). An ion’s contribution to the membrane potential is proportional to its ability to cross the membrane. P K : P Na : P Cl = 1.0: 0.04: 0.45 at rest .

Measuring the membrane potential difference:

Measuring the membrane potential difference Lumen diameter usually less than 1 micrometer and a resistance more than a million ohms Later connected to oscilloscope

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Measuring the Resting Membrane Potential It is measured with glass micropipets filled with solutions which conduct charge. The micropipet is inserted through the membrane into the cell. The voltmeter measures the difference in electrical charge between two points, in other words, the potential difference; it is measured in millivolts (mV). F5-32 The resting membrane potential is measured on a relative scale. The reference electrode is placed in the extracellular fluid. The extracellular fluid is designated as the ground and assigned a charge of 0 mV. In reality, the extracellular fluid is not neutral and has an excess of +ve charge that balances the excess of -ve charge in the cell. The resting membrane potential is between -40 to -90 mV in nerve and muscle.

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Only about 1/3,000,000 to 1/100,000,000 of the total positive charges inside the fiber must be transferred.

Generation of RMP:

Generation of RMP

Active Transport of Sodium and Potassium Ions Through the Membrane-The Sodium-Potassium (Na+-K+) Pump :

Active Transport of Sodium and Potassium Ions Through the Membrane-The Sodium-Potassium (Na+-K+) Pump

Further reading:

Further reading End plate potential Generator potential Graded potential Action potential Depolarisation Hyperpolarisation Role of connexons Role of ligand gated channels Role of different ion concentrations in ecf to rmp Role of calcium Role of Hydrogen Role of sodium, potassium and chloride ions

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