Thermoregulation and the ultradian basic rest-activity cycle.
Daily life involves interactions with the external environment. In rats these apparently spontaneous interactions, often associated with the search for food, alternate with periods of rest in both the dark and light periods of the 24-hour day. Kleitman, in whose laboratory rapid eye movement sleep was discovered, referred to the temporal pattern as "the basic rest-activity cycle." The active periods of the basic rest-activity cycle occur approximately every 1-2 hours in an irregular stochastic pattern that has been described (perhaps unhelpfully) as ultradian rhythmicity. Both the spontaneous interactions and those evoked by salient, potentially threatening environmental events are accompanied by increases in brown adipose tissue (BAT) temperature of approximately 1°C. The heat produced in BAT contributes to associated increases in the temperature of the brain (approximately 0.8°C) and the body (approximately 0.6°C). These temperature changes require extension of the conventional "homeostasis" framework of temperature regulation. They may function to facilitate the cognitive processing that underlies the vital decision making necessary for safe and effective interaction with the external environment.
['Blessing|William W|WW|']
D000204:Activity Cycles D002001:Adipose Tissue, Brown D001831:Body Temperature D001833:Body Temperature Regulation D006801:Humans D012146:Rest
brown adipose tissue BAT homeostasis basic rest–activity cycle brain temperature brown adipose tissue thermogenesis eating emotional hyperthermia hippocampal theta rhythm stochastic timing stress-induced hyperthermia thermogenesis