Ion and membrane changes in the brain during anoxia.

Anoxia has two main effects on the brain, a rapid, reversible loss of function and permanent damage when the period of anoxia exceeds a critical length of time. The initial loss of function is related to a K+-conductance increase of the nerve membrane, leading to reduction of membrane resistance and hyperpolarization. After a few minutes, a non-selective increase of membrane permeability mediates rapid transfer of ions between the intra- and extracellular spaces. The subsequent rise of intracellular Ca2+ concentration may be responsible for the nerve cell death.