Membrane voltages exist across almost all animal cells. In which cells are they largest?

1. Ionic concentration differences across a semipermeable membrane create a voltage in almost every animal cell. 2. The largest of these voltages are found in nerve and muscle cells. 3. Those are exactly the cells that have to fire, so the largest potentials sit where they are used. 4. Maintaining them is expensive, taking a quarter of the energy a cell uses. _Source: OpenStax College Physics (CC BY 4.0), Ch 20 "Electric Current, Resistance, and Ohm's Law", section Nerve Conduction_