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Ionic basis of the membrane potential

The key feature in maintaining a voltage difference between a neuron and the external world is the cell membrane which has the property of selectively allowing different ions in and out of the cell. There are many different ions in the intra- and extracellular media. For our purposes, the most important are calcium [Ca], potassium [K], sodium [Na], chloride [Cl], and magnesium [Mg]. Potassium and sodium have a single positive charge per ion, chloride has a single negative charge, and calcium and magnesium have two positive charges per ion. Positive ions are called cations and negative are called anions.


G. Bard Ermentrout