sleep

sleep vi.

1. [techspeak] To relinquish a claim (of a process on a multitasking system) for service; to indicate to the scheduler that a process may be deactivated until some given event occurs or a specified time delay elapses. 2. In jargon, used very similarly to v. block; also in `sleep on', syn. with `block on'. Often used to indicate that the speaker has relinquished a demand for resources until some (possibly unspecified) external event: "They can't get the fix I've been asking for into the next release, so I'm going to sleep on it until the release, then start hassling them again."

--The Jargon File version 4.3.1, ed. ESR, autonoded by rescdsk.

Historically, sleep was thought to be a temporary death. Sleepers would have no conscious control or volition. This influenced scientific thought for a long while, even up into the beginning of the twentieth century. Many researchers and scientists believed that sleep was a rest for the mind when it went into was completely cut off from the rest of the body. Today though, we know many of these thoughts to be untrue. During sleep, the brain is not cut off from the body; in fact, it very strictly controls the body during resting hours. In addition, we know that the brain is not merely in torpor during sleep, but actually undergoes many biological processes.

The path followed by sleepers has been well documented by twentieth century researchers. The journey of sleep starts out with the soon to be sleeper in a relaxed state of alpha wave production. Contrary to myth, the sleeper does not slowly drift into sleep. Rather, there is a rapid changeover to somnolence over the course of about a minute. During this changeover, the alpha waves of a relaxed state change over to theta waves. This signifies stage one sleep, the lightest of four distinct stages. During stage one sleep, the individual may experience broken or fragmented hallucinations that lack form. Also during this time, brain waves continue to slow in frequency and muscles relax throughout the sleeper's body. After a point, stage two sleep is achieved. During stage two sleep, theta brain waves are still the dominant pattern in a sleepers brain, however, these theta waves are interrupted by spindles and K complexes. Spindles are brief periods of beta wave activity that show up during stage two sleep. K complexes are high amplitude, high frequency waves that show up individually also in stage two sleep. Approximately twenty minutes after falling asleep, the sleeper moves into stage three sleep. This state is categorized by a switch into low frequency delta waves, relaxed muscles, slowed cardiac and pulmonary rates, lower blood pressure, and a slowing of digestion. Later, the sleeper shifts over to stage four sleep. This is the deepest stage of sleep, and it is difficult to rouse an individual from this state. After this stage, though, the sleeper begins to reverse the process, going back to stage three and then to stage two sleep. Instead of going back to stage one though, a new phenomenon occurs. Brainwaves that had been in the slow delta frequency, switch over into the beta range of normal conscious thought. At the same time, all voluntary muscles relax while the eyes start to move rapidly under the eyelids. This cycle of sleep, known as REM (Rapid Eye Movement) sleep, is the time when dreams occur. It lasts for three to ten minutes. The process described above describes the first sleep cycle. Each cycle lasts for about ninety minutes. Stage one sleep occurs only in the first and last sleep cycles: right after falling asleep and right before waking up. The amount of time spent in stages three and four sleep also decrease every cycle. The brain goes through lighter and lighter sleep as the night progresses. The time spent in these deeper sleeps is replaced with REM sleep so that in the cycle before waking, an individual may experience up to forty-five minutes of dreaming.

Sleep is strictly controlled by the brain. More specifically, the brainstem and hypothalamus. The brainstem has two specialized areas that help control sleep: the raphe nuclei and the locus coeruleus. These areas use the neurotransmitters, noradrenaline, serotonin, and acetylcholine to control sleep. These areas are in turn controlled by our circadian rhythms. Circadian rhythms are our internal clocks that tell the body when to undergo different processes. Using a mixture of hormones and nervous system activity, the circadian clock keeps an almost perfect twenty-five hour day. Since a day on Earth is only twenty-four hours though, the circadian clock requires constant updates to keep it running at the proper time. These updates are received from the external environment. In humans, the suprachiasmatic nuclei, found next to the thalamus, receives direct sensory information from the eyes to help regulate the internal clock.

Sleep is required for well being. People who are deprived of sleep will begin to fall apart physically and mentally. Studies in rats have shown what happens to organisms that go without sleep. The rats would become feverish and, even though their appetite increased, they would lose weight. In addition to these symptoms, the rats would cease to groom themselves, and also developed lesions on their skins. The rats body temperatures would begin to drop as well, and they would eventually die. While, for obvious reasons, this experiment can't be repeated with humans, it stands to reason that a human deprived of sleep long enough would show many of the same symptoms and maladies of sleep deprivation. One reason that these symptoms may occur is that several hormones are secreted during sleep. These hormones tell cells to repair themselves as well as promoting healing on a tissue level. Scientists believe that the secretions occur during the third and fourth stages of sleep when delta waves are produced. People deprived of delta sleep will begin to develop generalized muscle aches over a period of several weeks to months.

With the discovery of REM sleep, research opened up on dreams and dreaming. Scientists have found that dreams are carried out by almost all of the brain. Activity begins in the lower, more primal regions of the brain and, from there, spreads to the higher more advanced parts of the brain like the neocortex. While dreaming, rapid frequency beta waves are produced, these waves are indicative of concentration and mental activity. During dreams, activated parts of the brain, not knowing that they are asleep, send messages to muscles telling them to move. However, knowing that the brain is asleep, the brainstem sends out messages that cancel the orders sent by the motor controllers in the brain. If this were not the case, dreamers would act out the dream scenes with possibly horrible results. The brainstem allows many functions to be affected by dreaming however. Muscles controlling the eyes and ears are allowed to flex (internally in the case of the ears) trying to see or hear what is being dreamt about. At the same time, heart and respiratory rates increase. This corresponds with an increase in blood flow to the brain to support its flurry of activity.

Many theories exist that attempt to explain why people dream. One researcher suggests that dreaming is exercise for the brain. In the young, it would help to establish neural connections, and in the mature would make sure that everything is in working order. Another theory suggests that dreams are used to program instinctual behaviors. Dreams teach the brain to do things that at first are only available to us in our genetic code. Yet another theory tells us that dreaming is a way to reinforce our memory. Dreams would reactivate the circuits in our brain where memory is stored, thus strengthening them. There is evidence to help hold up this theory in that those deprived of REM sleep often have trouble learning and remembering. Sigmund Freud, a famous psychologist, theorized that dreams were the brains way of showing repressed impulses and desires to the conscious mind. However, since the conscious mind doesn't want to see much of what is being shown, the dreams come in code. Instead of being forthright, the images in dreams come in symbols and codes that may be interpreted by those who know what they mean. This may be the reason that many people from many different cultures and areas report having dreams with similar themes. These themes include falling, flying, and being chased, as well as the presence of certain animals, fire, and water.

During sleep, an individual may experience scary or terrifying experiences. These tend to fall in to one of two categories: nightmares and night terrors. Nightmares occur during REM sleep. They occur as normal dreams that in some way scare the dreamer. Depending on how horrifying the dream is, the sleeper may stay asleep and continue to experience the dream, or wake in attempt to escape it. In the latter case, nightmares are often remembered by the now awake individual. Night terrors though are a completely different story. Affecting mostly young children, night terrors occur during delta sleep. The child will suddenly wake screaming or crying with very little or no memory of what occurred other than the fact that it was terrifying. He or she may continue to scream or cry for several minutes before calming down. Often the child will then return to sleep and have mostly or entirely have forgotten about the experience by morning. The adult versions of night terrors are called incubus. During stage four sleep, a sufferer of this phenomenon will suddenly wake up. This rousing is accompanied by a feeling of weight on the chest as well as an indescribable feeling of anxiety. The sufferer will not have any memory of any dreams though that caused this state.

"Methought I heard a voice cry "Sleep no more!
Macbeth does murder sleep," the innocent sleep, (2.2.33)
Sleep that knits up the ravell'd sleave of care,
The death of each day's life, sore labour's bath,
Balm of hurt minds, great nature's second course, (2.2.36)
Chief nourisher in life's feast,--"

--From "Macbeth -- Act 2 Scene 2" by William Shakespeare

Just a moment of rest at the twilight of the day, yet also a gateway into sublimity and the unconscious mind, we rarely can sleep well if around someone we don't trust or like. But being in the presence of a trusted or loved one, we can instantly drift, without hesitation or fear. Macbeth knows this, as he fears that by betraying the trust of sleep, he has actually 'murdered' sleep for himself, sleep that is precious and the "Chief nourisher in life's feast,".

In these lines and the scene before, Macbeth has not only murdered another human being, and not only sleep, but trust and innocence as well, the qualities of sleep. We all sleep in our beds and under the roofs of our houses so soundly, because we trust these places and that warmth that is trust envelopes us as sleep. Like angels coming and sprinkling glittering jewels of sleep on our persons. If one day I were to lose sleep over something I have done, like Macbeth, who will "Sleep no more!", I will surely know that I have lost something inside of me.

The fear, during childhood, of monsters and demons, that haunt us, just before we fade away, pulling us back to the waking world, returns as guilt and sorrow and other psyche-polluting creatures, in our adulthood, and then we begin to treasure how immeasureably beautiful the simple act of resting our heads and laying down our bodies truly is. Metallica sings of these childhood fears, in "Enter Sandman" where James Hetfield, the lead singer admonishes the sleepy protagonist to "Say your prayers, little one," an appropriate piece of advice.

Tonight before I sleep, I will say a prayer, I think, of gratitude for my lively sleep.

Some Sleep Facts

• Your heart can stop beating for as long as 9 seconds while you're asleep.
• Sleep deprivation lasting more than 48 hours typically causes hallucinations and psychosis.
• The world record for going without sleep is 11 days (264 hours and 12 minutes) a feat considered extremely dangerous by sleep researchers.
• 30 million Americans suffer from sleep disorders. Most men begin having problems falling asleep in their mid-twenties; women have the same difficulty during their mid-forties.
• While normal sleepers change body positions about 30 times per night, insomniacs may toss and turn more than 100 times.
• Dream sleep has been observed in all animals studied except the spiny anteater.
• Sleep studies show that if your sleeping partner is absent in your sleep, you'll almost always mover over to the side the bed normally occupied by him or her. (I know for a fact I do.)
• An afternoon nap is healthy. One study indicates that afternoon nappers are 30 percent less likely to suffer coronary artery disease, although the reasons behind this are not yet known.
• Humans stay awake much longer than many animals. Bats, cats, porcupines, lions, gorillas, and opossums sleep 18 to 20 hours a day, and some woodchucks snooze for as long as 22 hours.
• Pigeons frequently open their eyes during sleep to watch for predators. The dolphin, remarkably, only "half" sleeps: its brain shuts down only one hemisphere at a time.
• Horses and rats dream 20 percent of the time during sleep. Cows kept in barns dream 40 minutes per night, while cows sleeping in meadows dream only half as much.

Sleep (?), obs.

imp. of Sleep. Slept.

Chaucer.

© Webster 1913.

Sleep, v. i. [imp. & p. p. Slept (?); p. pr. & vb. n. Sleeping.] [OE. slepen, AS. slpan; akin to OFries. slpa, OS. slapan, D. slapen, OHG. slafan, G. schlafen, Goth. slpan, and G. schlaff slack, loose, and L. labi to glide, slide, labare to totter. Cf. Lapse.]

1.

To take rest by a suspension of the voluntary exercise of the powers of the body and mind, and an apathy of the organs of sense; to slumber.

Chaucer.

Watching at the head of these that sleep. Milton.

2. Figuratively: (a)

To be careless, inattentive, or uncouncerned; not to be vigilant; to live thoughtlessly.

We sleep over our happiness. Atterbury.

(b)

To be dead; to lie in the grave

Them also which sleep in Jesus will God bring with him. 1 Thess. iv. 14.

(c)

To be, or appear to be, in repose; to be quiet; to be unemployed, unused, or unagitated; to rest; to lie dormant; as, a question sleeps for the present; the law sleeps

How sweet the moonlight sleep upon this bank! Shak.

© Webster 1913.

Sleep, v. t.

1.

To be slumbering in; -- followed by a cognate object; as, to sleep a dreamless sleep.

Tennyson.

2.

To give sleep to; to furnish with accomodations for sleeping; to lodge.

Blackw. Mag.

To sleep away, to spend in sleep; as, to sleep away precious time. -- To sleep off, to become free from by sleep; as, to sleep off drunkeness or fatigue.

© Webster 1913.

Sleep, n. [AS. slp; akin to OFries. slp, OS. slap, D. slaap, OHG. slaf, G. schlaf, Goth. slps. See Sleep, v. i.]

A natural and healthy, but temporary and periodical, suspension of the functions of the organs of sense, as well as of those of the voluntary and rational soul; that state of the animal in which there is a lessened acuteness of sensory perception, a confusion of ideas, and a loss of mental control, followed by a more or less unconscious state.

Chaucer.

O sleep, thou ape of death. Shak.

Sleep is attended by a relaxation of the muscles, and the absence of voluntary activity for any rational objects or purpose. The pulse is slower, the respiratory movements fewer in number but more profound, and there is less blood in the cerebral vessels. It is susceptible of greater or less intensity or completeness in its control of the powers.

Sleep of plants Bot., a state of plants, usually at night, when their leaflets approach each other, and the flowers close and droop, or are covered by the folded leaves.

Syn. -- Slumber; repose; rest; nap; doze; drowse.

© Webster 1913.