6 Control systems
Measurements of thermoregulation, respiration and metabolic depression in the edible dormouse (Myoxus glis) during the early stages of torpor, hibernation and aestivation, indicate remarkable similarities in the profile of physiological changes for all three adaptive phenomena, suggesting that they are controlled by essentially the same mechanism. The capacity for adaptive hypothermia in animals is clearly determined genetically and is manifested in cells from many different tissues. Nevertheless, we have known for a long time that control centres in the brain exist which coordinate behavioural (feeding, drinking, reproductive) as well as physiological (circulatory, respiratory) functions, and establish cyclical rhythms for these functions which relate them to daily, monthly and seasonal changes in an animal's habitat.
What three functions must the brain fulfil to achieve this coordination?
It must act as a central receptor, integrating signals such as ambient light levels, daylength and temperature with internal indicators of physiological state.
It must contain an internal ‘clock’ that can be set to operate with reference to environmental changes.
It must contain command centres, which adjust body temperature, metabolism, respiration, circulation and behaviour to adapt to prevailing conditions in the habitat.