Overview of physiological processes during sleep

Physiological regulation can be defined as the integrated neural control mechanism underlying somatic, autonomic, and neuroendocrine activity. Such an integration occurs mostly at hypothalamic level. Physiological regulation is intrinsically heterogeneous between non-rapid eye movement (NREM) and rapid eye movement (REM) sleep. During NREM sleep, it is aimed at the maintenance of body homeostasis at a low level of energy expenditure. During REM sleep, the cardiorespiratory instability and the thermoregulatory impairment are indicative of a derangement of the integrative neural regulation of physiological functions. However, the finding that osmoregulation is maintained during REMS suggests that this derangement does not affect the whole hypothalamus.