It is necessary to use the concept of ions which will be familiar to those who have taken chemistry. For example the chemical name for common table salt is sodium chloride. The chemical symbol is NaCl. When NaCl is dissolved in water it breaks up into its constituent atoms, namely sodium (Na) and Chlorine (Cl). When these atoms break away from each other sodium atom has a positive charge and the chlorine atom a negative charge. Thus these atoms are said to be ionized. Other chemical compounds often also carry positive or negative charges and are thus said to be ionized. Movement of these charged particles across neural membranes results in an electrical current and we thus refer to an electrophysiological event.
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