Decreased oxygen tension (hypoxia) is an emergency situation that subjects the body to stress (stress), which causes multiple changes, some specific or is due to decreased oxygen and other general information, such as the syndrome adaptation. If the animal survives an evolution of the phenomena observed in three phases: a) acute or alarm reaction; b) adaptation or acclimatization; c) mismatch or deacclimation or decompensation. The nervous system, initially stimulated by hypoxia modifies the function of the adrenal cortex and medulla. The action of the crust is because the central nervous action causes increased secretion of adrenocorticotropic hormone by the pituitary pars distalis. The action on the adrenal medulla consists of a stimulus on the upper sympathetic centers (hypothalamus, etc.), speaking the lower spinal cord and greater splanchnic nerves and produces a strong adrenaline r...