... potential represents its stability, when not stimulated or firing. The cell's charge is -70 mV, the cell is negatively charged whereas the outside is less. The membrane controlling ions moving in and out the cell through ion channels using ion pumps (sucking in or extruding the ions) creates a negative voltage due to unequal distribution of ions: - The protein anions, which are too large to pass the semi-permeable axon's membrane. - Sodium cations (Na+) are pumped out of the cell. The channels allowing the sodium back into the cell are shut during the resting membrane potential. - Sodium and potassium (K+) ions lead to an excess of positively charged ions outside the cell, although some chlorine anions, (Cl-), are also present there. Every neuron has its threshold: it is believed to be around -55mV in mammals, although it can vary from one neurone to another. If the stimulus is strong enough ...

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