ABSTRACT

Maintenance of core body temperature within narrow bounds and the constancy of composition and volume of body uids in mammals are probably the most iconic manifestations of homeostasis in mammals. The ability to keep the internal environment of their bodies as unchanged as possible in the face of hostile environments is one of the reasons for mammals being able to populate and survive in many regions of the planet. Whereas mammals that inhabit the cooler and temperate regions of the earth are less likely to experience extremes of high ambient temperatures or insuf-cient supply of water for maintaining bodily hydration, this is not the case for those

7.1 Thermoregulation and Body Fluid Homeostasis .......................................... 111 7.2 Thermoregulatory Responses to Increasing Core Body Temperature ......... 112 7.3 Homeostatic Responses to Dehydration Resulting from Sweating,

Panting, or Saliva Loss ................................................................................. 112 7.3.1 Vasopressin Secretion, Thirst, and Natriuresis ................................. 112 7.3.2 Thermoregulatory Inhibition of Sweating and Panting .................... 113

7.4 Osmoreceptor Mediation of Inhibition of Panting ....................................... 114 7.5 Site of Cerebral Osmoreceptors Inuencing Thermoregulatory Panting ..... 115 7.6 Effect of Drinking on Thermoregulation ..................................................... 116 7.7 Concluding Remarks .................................................................................... 119 Acknowledgments .................................................................................................. 120 References .............................................................................................................. 120

species that exist in warmer and drier parts of the earth. The evolutionary emergence and survival of many mammalian species has resulted from adaptations that permit such animals to minimize and correct changes in core body temperature as well as decits in body uid volume and composition arising in hot, dry environments.