Overview of Physiological Processes During Sleep

Somatic and autonomic physiological regulation varies during the ultradian sleep cycle in mammals. The basic somatic features of nonrapid eye movement (NREM) sleep are thermoregulatory posture, a decrease in antigravity muscle activity, and slow eye movements. The basic somatic features of rapid eye movement (REM) sleep are skeletal muscle atonia, myoclonic twitches, and rapid eye movements. The autonomic phenomena of NREM sleep are indicative of an integrative neural regulation of the systemic physiological functions of respiration, circulation, and thermoregulation, maintaining the homeostasis of the organism at a lower level of energy expenditure compared with wakefulness. In contrast, the autonomic phenomena of REM sleep are indicative of a suspension of the integrative neural regulation (poikilostasis) of such physiological functions.