The problems of neurons with long axons.

Neurons with long axons are unique among cells in having to maintain a very large area of membrane. In this respect they have problems in common with red cells: the latter are separated from the source of their metabolites in time, the former by distance. In equilibrium, maintenance mechanisms are adequate; but in conditions of energy deprivation or deprivation of antioxidant substances such as glutathione and alpha-tocopherol, or when the transport of materials within the neuron is physically obstructed, the system may break down and the longest fibres will always suffer first. The problems are logistical, just as are those of red cells. The association between red-cell disease and neuropathy is not entirely fortuitous.