There are many different factors that influence sleep. These can include the presence of recent sleep or wakefulness, the patient’s age, the time of day, and other factors, like stress, environmental conditions, exercise, and certain chemicals. As an infant, sleep starts in REM sleep. Babies have a shorter sleep cycle, alternative between REM and non-REM sleep every 50 minutes, instead of every 90 minutes in adults. The recent sleep history will impact the sleep pattern of a given night’s sleep. An irregular sleep schedule or missing a night’s sleep will affect the pattern of sleep so there is more non-REM sleep. Drugs like alcohol will suppress REM sleep but this rebounds as the night progresses. The more REM sleep a person has, the more frequently the person will awaken. While it is common to get sleep in one big block, this isn’t the only possible sleep pattern. Many cultures, particularly in tropical areas, will have an afternoon nap among adults. Stores and buildings close so that people can get a one to two-hour nap. Napping follows the largest meal of the day and occurs during the hottest time of the day. Naps in most cases are between thirty minutes and sixty minutes. It is a good way for people who do not sleep well to catch up during the day.
CIRCADIAN RHYTHMS It is generally common for adults to get 16 hours of wakefulness with 8 hours of sleep. There is a small bundle of nerve cells that promote or initiate sleep. There are areas in the brainstem and hypothalamus that are involved in wakefulness. The tuberomammillary nucleus or TMN releases histamine to cause wakefulness. This is why anti-histamines promote sleep. Other neurons will make orexin or hypocretin that stimulates the arousal centers in the cerebral cortex. The hypothalamic nucleus called VLPO or ventrolateral preoptic nucleus connects to the arousal centers, promoting sleep. There is mutual inhibition between the sleeppromoting neurons and the wake-promoting neurons that cause stable wakefulness or sleep. The VLPO and the TNM operate opposite to one another in order to have a normal sleep pattern.
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