Figure 4.

ATP supply and consumption in myelinated axons. A, ATP production by axonal mitochondria increases nonlinearly with axon diameter. B, ATP use on housekeeping, resting potentials, and action potentials all increase with axon diameter. ATP use on presynaptic processes was considered negligible. C, For axons larger than 0.9 μm in diameter, the ATP produced by axonal mitochondria can comfortably sustain the observed action potential firing rate, resting potential, and housekeeping processes. For smaller axons, there is up to a 38% deficit in the ATP available.