The malnutrition many alcoholics suffer deprives them of important cofactors for the oxidative metabolism of glucose. Neural tissues depend on this process for energy, and disruption of the cycle would impair cell growth and function. Schwann cells produce myelin that wraps around the sensory and motor nerve axons to enhance action potential conduction in the periphery. An energy deficiency in Schwann cells would account for the disappearance of myelin on peripheral nerves, which may result in damage to axons or loss of nerve function altogether. In peripheral nerves, oxidative enzyme activity is most concentrated around the nodes of Ranvier, making these locations most vulnerable to cofactor deprivation. Lacking essential cofactors reduces myelin impedance, increases current leakage, and slows signal transmission. Disruptions in conductance first affect the peripheral ends of the longest and largest peripheral nerve fibers because they suffer most from decreased action potential propagation. Thus, neural deterioration occurs in an accelerating cycle: myelin damage reduces conductance, and reduced conductance contributes to myelin degradation. The slowed conduction of action potentials in axons causes segmental demyelination extending proximally; this is also known as retrograde degeneration.