Page 17 ”These ionic concentration gradients across the cell membrane constitute the driving forces (or chemical potentials) for ionic currents flowing through open channels in the membrane. In other words, the ionic concentration gradients act like DC batteries for cross-membrane currents.” First, the relation is mutual; it could be considered that there are chemical batteries. Second, the ionic currents flow not only through the membrane; they can flow also through the extracellular space. Furthermore, one must tell also when it flows. Third, the driving force of those DC batteries changes during operation.