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sleep

 [slēp]
a period of rest for the body and mind, during which volition and consciousness are in partial or complete abeyance and the bodily functions partially suspended. Sleep has also been described as a behavioral state marked by characteristic immobile posture and diminished but readily reversible sensitivity to external stimuli.

NREM and REM Sleep. Prior to the discovery and reporting of rapid eye movements during sleep, it was thought that sleep was a single state of passive recuperation in which the central nervous system was deactivated. Studies concerned with the measurement of central and autonomic activities during sleep have led to its division into two types: non–rapid eye movement (NREM) sleep, also called orthodox or synchronized (S) sleep; and rapid eye movement (REM) sleep (so called because of the rapid eye movements during this stage), also called paradoxical or desynchronized (D) sleep.

On the basis of electroencephalographic (EEG) criteria, NREM sleep is subdivided into four stages. Stage 1 is observed immediately after sleep begins or after momentary arousals and is characterized by low-voltage, mixed-frequency EEG tracing, with predominantly theta-wave activity (four to seven hertz, that is, cycles per second). Stage 2 is characterized by intermittent waves of 12 to 16 hertz, known as sleep spindles.Stages 3 and 4 consist of relatively high voltage EEG tracings with a predominance of delta wave activity (one to two hertz).

The EEG patterns of NREM sleep suggest that this is the kind of apparently restful state that supports the recuperative functions assigned to sleep. NREM sleep is increased after physical activity and has a relatively high priority among humans in the recovery sleep following extended periods of wakefulness.

Within 90 minutes after sleep begins, an adult progresses through all four stages of NREM sleep and then proceeds into the first of a series of REM periods of sleep. Brief cycles of about 10 to 30 minutes of REM sleep recur throughout the night, alternating with various stages of NREM sleep. With each cycle, NREM sleep decreases and REM sleep increases so that by the end of the night most of the sleep is REM sleep, which is when dreams occur. While everyone dreams every night, many do not remember dreaming; most people are aware, however, that they dream more just before rising.

In addition to the rapid eye movements that can be observed through closed eyelids, REM sleep can be recognized by complete relaxation of the lower jaw. Convulsions, myocardial infarction, and cardiac arrhythmias are more likely to occur during REM sleep. This is probably because of increased autonomic activity, irregular pulse, and fluctuations in blood pressure, which are all typical of REM sleep.
Patterns of Sleep. Although the average adult spends approximately 25 percent of total accumulated sleep in REM sleep and 75 percent in NREM sleep, the cyclic changes vary with individuals. The pattern of sleep, in addition to the REM and NREM states, also includes the periods of sleep and wakefulness within a 24-hour period.



Factors affecting the total sleep pattern include age, state of physical health, psychological state, and certain drugs. Newborns follow a pattern of several hours of sleep followed by a period of wakefulness. REM sleep occurs at the onset of sleep in infants; it rarely does in adults. As the child matures there is an increasing tendency toward longer periods of nocturnal sleep. Elderly persons sometimes return to the shorter periods of sleep that are typical of infants.
Benefits of Sleep. Sleep requirements vary greatly among individuals. Infants usually require 16 to 20 hours of total sleep during a 24-hour period, and the amount decreases as the child matures. An adult usually requires 6 to 9 hours of total sleep, and requirements continue to decrease with aging.



Most theorists agree that sleep has value as a recuperative and adaptive function in the lives of humans. The relatively high metabolic needs of mammals and birds to maintain a constant body temperature in a wide range of environmental temperatures suggests that the periodic decreases in metabolic rate and body temperature that occur in NREM sleep allow for recuperation and restitution of body tissues. For example, even though the function of stage 2 NREM sleep is not clear, approximately half of human sleep time is spent in this stage. It is also theorized that REM sleep provides a period of recuperation of mental activities and preparation for wakefulness. During REM sleep it is believed that there is increased metabolic activity in the brain so that during waking hours it is more receptive to new information and can assimilate it more easily.
sleep apnea syndrome episodes of apnea (cessation of breathing) occurring at the transition from NREM to REM sleep, with repeated wakening and excessive daytime sleepiness; it occurs most often in middle-aged, obese males and is thought to have several causes, one being collapse or obstruction of the airway with the inhibition of muscle tone that characterizes REM sleep. The condition is arbitrarily defined as more than five cessations of airflow for at least 10 seconds each per hour of sleep.
sleep disorders chronic disorders involving sleep; primary sleep disorders are classified as dyssomnias or parasomnias. Among the minor disorders are sleepwalking, sleeptalking, enuresis, bruxism (tooth grinding), and nightmares. Sleepwalking is not considered serious if it occasionally occurs in childhood. It should be considered pathological, however, if it persists into adulthood. Sleeptalking is common to many persons and, while it may annoy others whose sleep it may disturb, it is not considered pathological.



A sleep disorder occurring in early childhood, and not to be confused with nightmares, is sleep terror disorder. The child awakens with a scream, is in panic and cannot be consoled, and often is incoherent; the following morning, there is poor recall of the event. Treatment usually involves reassurance of the parents. Adults who experience night terrors often have some psychological problem requiring treatment. More serious disorders of sleep include persistent insomnia, narcolepsy, and chronic hypersomnia. Hypersomnia can occur with central nervous system damage or may be secondary to some physical and mental illnesses, particularly depression.
sleep terror disorder a sleep disorder of the parasomnia group, consisting of repeated episodes of pavor nocturnus (sleep terrors).

sleep

hypnophobia.

sleep

(slēp),
A physiologic state of relative unconsciousness and inaction of the voluntary muscles, the need for which recurs periodically. The stages of sleep have been variously defined in terms of depth (light, deep), EEG characteristics (delta waves, synchronization), physiologic characteristics (REM, NREM), and presumed anatomic level (pontine, mesencephalic, rhombencephalic, rolandic, etc.).
[A.S. slaep]

sleep

(slēp)
n.
A natural periodic state of rest for the mind and body, in which the eyes usually close and consciousness is completely or partially lost, so that there is a decrease in bodily movement and responsiveness to external stimuli. During sleep the brain undergoes a characteristic cycle of brain-wave activity that includes intervals of dreaming.
v.
To be in the state of sleep.

sleep

Rest resulting from a natural suspension of voluntary bodily functions and consciousness. Good sleep hygiene is regarded as a component of good health: it enhances the immune system, and is beneficial for common colds, cardiovascular disease, longevity, recuperation from injuries and productivity.

sleep

Sleep disorders Rest resulting from a natural suspension of voluntary bodily functions and consciousness. See Deep sleep, Delta sleep, Good habit, Light sleep, Microsleep, Non-REM sleep, Nocturnal sleep, Normal sleep, REM sleep, Twilight sleep. Cf Bad habit, Poor sleeping hygiene.

sleep

(slēp)
A physiologic state of relative unconsciousness and inaction of the voluntary muscles, the need for which recurs periodically. The stages of sleep have been variously defined in terms of depth (light, deep), electroencephalographic characteristics (delta waves, synchronization), physiologic characteristics, and presumed anatomic level (pontine, mesencephalic, rhombencephalic, rolandic).
[A.S. slaep]

sleep

The natural, regular, daily state of reduced consciousness and METABOLISM that occupies about one-third of the average person's life. Sleep requirements vary considerably in health, between about 4 and 10 hours in each 24 hour period. The purpose of sleep is unknown but prolonged deprivation is harmful, causing depression and mental disturbances, including hallucinations.

sleep

(slēp)
Physiologic state of relative unconsciousness and inaction of voluntary muscles, its need recurs periodically.
[A.S. slaep]

Patient discussion about sleep

Q. How to deal with sleeping problems? I wonder if anyone could help me. Here's the thing: I’ve been in school break for two months now and that means i usually go to bed at about 2 am, and I usually wake up with an alarm clock at 11 for breakfast then lunch immediately after breakfast. My problem is that I have problems sleeping, I usually stay an hour or two in bed trying to get some sleep.

A. My Dr. has me on Ambien cr,12.5 MG Tablets, and they work fine for me. I though i would see if they really worked about a month ago and did not take a pill before bed time, and i went right to sleep and slep for about 1 1/2 hrs and was awake the rest of the night, so i never fail to take a tablet every night when i lay down. Ask your dr. about this med.

Q. I go to sleep & use to wake up paralyzed in my sleep. I go to sleep & use to wake up paralyzed in my sleep. But not asleep, just laying there, eyes wide open paralyzed. I couldn't breath, I couldn't speak, move anything but my eyes. I could look around but I couldn't even breathe. This has happened a few times in my old house, once in my mother's house (she lived by the side of a graveyard), and then only once in my new house. What is it and what do you think is causing it?

A. I had the same problem but never at night...and it only happened during the day when I take nap. I will wake up and I can't move or talk, I can't open my eyes either. I've never been able to snap out of it though, I just have to lay there until I go back to sleep, and usually it doesn't happen when I wake up the next time. Needless to say I try NOT to take naps anymore, because it happens nearly every time.

Q. sleeping problems i"m waking up in the middle of the night and can't get back.

A. The first steps usually recommended are to improve sleep hygiene:
• Sleep only as much as you need to feel rested
• Keep a regular sleep schedule
• Avoid forcing sleep
• Exercise regularly for at least 20 minutes, preferably 4 to 5 hours before bedtime
• Avoid caffeinated beverages after lunch
• Avoid alcohol near bedtime: no "night cap"
• Avoid smoking, especially in the evening
• Do not go to bed hungry
• Adjust bedroom environment
• Deal with your worries before bedtime
These practices address many of the causes of sleep problems. However, sleep problems may result from many causes, so consulting a doctor may be wise.

Take care,

More discussions about sleep
References in periodicals archive ?
The connection between hours slept and weight wasn't significant for people 60 and older, says James Gangwisch, a psychiatric epidemiologist at Columbia, "probably because the sleep problems that are so common in older people obscure the link." (The analysis hasn't yet been published.)
Infants, having slept uninterruptedly for nine months in the womb, should sleep at least 12 hours (some said most of the time), but after six months of age the amounts could quickly diminish.
Participants who slept less than six hours every night were 27 per cent more likely to have atherosclerosis than those who slept seven to eight hours every night.
She suggests that these results could explain why some people in sleep clinics report being awake all night, even though their brain waves indicate that they slept. The findings might also guide researchers to drugs that could promote sleep by turning off select parts of the brain rather than the more-widespread neural areas that existing sleeping pills shut down.--C.B
Intriguingly, mothers reported that preschoolers who began co-sleeping as infants exhibited more self-reliance and social independence--such as settling disputes with playmates on their own--than did those who slept alone or started co-sleeping at later ages.
Peigneux's group used a positron emission tomography (PET) scanner to measure blood flow throughout the brains of 24 men ages 18 to 30 while they were awake or while they slept.
He also snored when he slept, another sign of sleep apnea.
Among a group of healthy elderly people tracked for an average of 13 years, those who had difficulty falling or staying asleep died from natural causes at a much higher rate than those who slept well, according to a report in January/February Psychosomatic Medicine.
So, the scientists next compared 13 men and women who habitually slept 6.5 hours or less per night at home with 14 men and women who regularly slept about 8 hours.
However, they caution that the numbers don't explain why some people slept more than others.
His body temperature remained nearly constant whether he slept or was awake.
Yet as recently as 200 years ago in Europe, people slept in two nightly phases of 4 to 5 hours each.