The sleep/wake cycle and the 24-hour rhythm of the body temperature are regulated by a circadian periodicity that originates from the suprachiasmatic nucleus in the hypothalamus. In the morning we wake up, our body temperature increases from the nocturnal level, and we are able to be active throughout the day. In the late evening, when it is dark, we normally go to bed, and after a while we fall asleep.
With reference to the EEG pattern, sleep is divided into five different stages:
• Stage 1: Light or drowsy sleeping representing the transitional stage between being awake and sleeping, lasting 5 to 10 minutes in the late evening. During this stage breathing becomes slow and regular. The heart rate decreases. Episodes of stage 1 sleep occur during the night, with increased frequency and length in the latter part of the night.
• Stage 2: Sleep becomes deeper and the muscle tone decreases. Approximately 40 to 50% of a typical night is spent in stage 2.
• Stages 3 and 4: Referred to as deep sleep, delta sleep, or slow-wave sleep (SWS). Waking from these stages is more difficult than from stages 1 and 2. During SWS, growth hormone is released from the hypothalamus. Many restorative processes, such as healing of injuries and immunological processes necessary for defense against infections or malignancies are most active during SWS (Stanley, 2005).
• Stage 5: During rapid-eye-movement (REM) sleep, dreams are more common than in other sleep stages. REM sleep may occur in four or five periods throughout the night at intervals of 60 to 90 minutes and with increasing length throughout the night. REM sleep has been attributed to emotional well-being and memory (Stanley, 2005).
The longest periods of SWS are seen in children, with a substantial reduction in young adults, and these periods are even shorter or sometimes absent in the elderly. Their total sleep is shortened even though they spend more time in bed. The sleep of the elderly is not only more superficial but also more fragmented than in younger people (Kales et al., 1974).
Sleep and wakefulness are governed by a circadian and a homeostatic mechanism. The sleep/wake cycle is generated by a circadian rhythm that originates from the suprachiasmatic nucleus of the hypothalamus. This cycle makes it easier to fall asleep at the common time of the 24-hour period, most commonly in the evening or at night, whereas falling asleep in the daytime is more difficult or sometimes impossible. The homeo-static mechanism generates increased sleepiness and prolonged sleep after prolonged wakefulness, and consequently the amount of sleep is shorter if sleep takes place after a shorter time than usual in the waking state (Stanley, 2005).
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A Guide to Natural Sleep Remedies. Many of us experience the occasional night of sleeplessness without any consequences. It is when the occasional night here and there becomes a pattern of several nights in arow that you are faced with a sleeping problem. Repeated loss of sleep affects all areas of your life The physical, the mental, and theemotional. Sleep deprivation can affect your overall daily performance and may even havean effecton your personality.