<P> Chloride channels are present in all types of neurons . With the chief responsibility of controlling excitability, chloride channels contribute to the maintenance of cell resting potential and help to regulate cell volume . </P> <P> Voltage - gated proton channels carry currents mediated by hydrogen ions in the form of hydronium, and are activated by depolarization in a pH - dependent manner . They function to remove acid from cells . </P> <P> Phylogenetic studies of proteins expressed in bacteria revealed the existence of a superfamily of voltage - gated sodium channels . Subsequent studies have shown that a variety of other ion channels and transporters are phylogenetically related to the voltage - gated ion channels, including inwardly rectifying K channels, ryanodine - inositol 1, 4, 5 - triphosphate receptor Ca channels, transient receptor potential Ca channels, polycystin cation channels, glutamate - gated ion channels, calcium - dependent chloride channels, monovalent cation: proton antiporters, type 1, and potassium transporters . </P>

How many gates control flow of na+ through voltage-gated na+ channels