) in which fast and low-amplitude waves prevail. This phase of sleep is accompanied by other physiological alterations, such as cardiac and respiratory irregularities, and changes in blood pressure. It is also a period of intense dreams.
Conversely, non-REM sleep is characterized by the "drowsiness of all autonomic functions, as evidenced by an EEG trace characterized by large and slow waves.
The phases of REM sleep, interspersed with longer periods of deep sleep, last for 15-20 minutes each and are repeated approximately every two hours. During the night the phases of orthodox sleep progressively decrease and increase in duration and duration. intensity those of the REM type, up to the longest moment that precedes awakening.
and by the increase of the cutaneous one. During non-REM sleep, therefore, thermoregulation is oriented towards a reduction of the body temperature itself. It also seems that the generalized decrease in metabolic activity is mediated by a thermoregulatory control that anticipates the onset of sleep; therefore, the reduction of metabolic processes seems to be not only the consequence, but also a necessary requirement to favor falling asleep.During the non-REM sleep phase, the body still maintains its thermoregulatory capacity; consequently, similarly to what occurs in the waking state, it responds to an increase in ambient temperature with polypnea, peripheral vasodilation, sweating, reduction of the underlying metabolic processes to the optional thermogenesis and assuming a posture favoring thermal dispersion; vice versa, when the ambient temperature decreases, during non-REM sleep it is possible to appreciate cutaneous vasoconstriction, piloerection, increase in optional thermogenesis and, limited to phases one and two, the appearance of The above described does not occur in the REM sleep phases, during which the hypothalamus loses its ability to thermoregulate, to the point of allowing a paradoxical behavior to be appreciated with the appearance of cutaneous vasoconstriction in animals exposed to heat and vasodilation in those exposed to cold.
Consequently, during REM sleep the only solutions to safeguard the organism from excessive temperature excursions are represented by awakening or passing to a non-REM sleep phase. Cerri et al., 2005, for example, have shown how "exposure of rats to cold environmental conditions, such as to lead to the loss of thermoneutrality, produced a reduction of about 80% in the duration of REM sleep normally expressed in this species.
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