Specific physiological situations, like deep diving or hibernation, and many special conditions expose animals and their systems to the effect of subnormal or supranormal thermodynamic challenges. Humans, and other animals, are exposed to variables like temperature and pressure as consequence of challenges in special environments such as the depth of the sea or the outer space. The function of central nervous system is in these cases one of the limiting factors, determining the boundaries for survival (ocurrence of neurological signs and symptoms). Adaptive mechanisms to extreme temperatures and pressures have been observed in areas of the brain, like the hippocampus. Such adaptive changes possibly allow behavioral performance at temperatures and pressures beyond normal ranges. These mechanisms are particularly important for hibernating and the deep diving animals. The performance of Cetaceans, and possibly in the adaptation of human divers working at the great depths (e.g. at the North Sea oil wells) depend on adaptation of their nervous system to the high pressure environments they challenge.
