Nernst equation resting membrane potential

Traditionally concepts of ion selective permeation of biological membranes have centered on differences in the effective radii of hydrated nuclei. An example of that perspective derives from consideration of the resting membrane potential, E, which in the squid axon is approximated by the Nernst equation... 

PERMEABILITY PERMEABILITY CONSTANT MEMBRANE POTENTIAL ACTION POTENTIAL DEPOLARIZATION GOLDMAN EQUATION NERNST EQUATION RESTING POTENTIAL THRESHOLD POTENTIAL PATCH-CLAMP TECHNIQUE Membrane protein dynamics,... 

Diffusion potentials for the primary biological ions (potassium, sodium, and chloride) represent the primary source of the resting membrane potential. The diffusion potential for a given ionic species can be calculated from the modified Nernst equation developed by Hodgkin and Huxley. The equation is ordinarily written as... 

Quantitatively, the usual resting membrane potential of — 70 mV Is close to but lower In magnitude than that of the potassium equilibrium potential calculated from the Nernst equation because of the presence of a few open Na channels. These open Na channels allow the net Inward flow of Na" ions, making the cytosolic face of the plasma membrane more positive, that is, less negative, than predicted by the... 

It would appear that changes in the intracellular or extracellular concentration of potassium ions markedly alter the resting membrane potential. For this reason, neurophysiologists treated an excitable cell as if it were an electrochemical, or Nernst, cell. The resting potential for one permeant species could therefore be explained by the familiar Nernst equation ... 

Equilibrium potentials calculated at 37°C from the Nernst equation. Calculated assuming a —90 mV resting potential for the muscle membrane and assuming that chloride ions are at equilibrium at rest. 

The behavior of an ion type is described quantitatively by the Nernst equation (3). A /g is the membrane potential (in volts, V) at which there is no net transport of the ion concerned across the membrane (equilibrium potential). The factor RT/Fn has a value of 0.026 V for monovalent ions at 25 °C. Thus, for K, the table (2) gives an equilibrium potential of ca. -0.09 V—i. e., a value more or less the same as that of the resting potential. By contrast, for Na ions, A /g is much higher than the resting potential, at +0.07 V. Na" ions therefore immediately flow into the cell when Na channels open (see p. 350). The disequilibrium between Na" and IC ions is... 

Thus, a 10 1 transmembrane gradient of a single monovalent ion, say potassium, will generate a membrane potential of 58 mV. See Resting Potential Action Potential Depolarization Threshold Potential Nernst Equation Goldman Equation Patch-Clamp Technique... 

An examination of the relationship of [K" ]o] and [K+]i] in the Nernst equation shows that an increase in the [K" ]o will result in a decrease in the membrane resting potential (less negative). Changes in the extracellular concentration of another ion (Na+, Ca+", Cl > may also modify the resting potential. 

Open-circuit potential (OCP) — This is the - potential of the - working electrode relative to the - reference electrode when no potential or - current is being applied to the - cell [i]. In case of a reversible electrode system (- reversibility) the OCP is also referred to as the - equilibrium potential. Otherwise it is called the - rest potential, or the - corrosion potential, depending on the studied system. The OCP is measured using high-input - impedance voltmeters, or potentiometers, as in - potentiometry. OCP s of - electrodes of the first, the second, and the third kind, of - redox electrodes and of - ion-selective membrane electrodes are defined by the - Nernst equation. The - corrosion po-... 

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