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Encyclopedia > Sleep

Sleep is a natural state of bodily rest observed throughout the animal kingdom. It is common to all mammals and birds, and is also seen in many reptiles, amphibians and fish. Look up Sleep in Wiktionary, the free dictionary. ... See Animal. ... Orders Subclass Monotremata Monotremata Subclass Marsupialia Didelphimorphia Paucituberculata Microbiotheria Dasyuromorphia Peramelemorphia Notoryctemorphia Diprotodontia Subclass Placentalia Xenarthra Dermoptera Desmostylia Scandentia Primates Rodentia Lagomorpha Insectivora Chiroptera Pholidota Carnivora Perissodactyla Artiodactyla Cetacea Afrosoricida Macroscelidea Tubulidentata Hyracoidea Proboscidea Sirenia The mammals are the class of vertebrate animals primarily characterized by the presence of mammary... For other meanings of bird, see bird (disambiguation). ... Orders  Crocodilia - Crocodilians scary crocodiles. ... For other uses, see Amphibian (disambiguation). ... For other uses, see Fish (disambiguation). ...


In humans, other mammals, and a substantial majority of other animals which have been studied — such as fish, birds, ants, and fruit-flies — regular sleep is essential for survival. However its purposes are only partly clear and are the subject of intense research.[1] Wikipedia does not yet have an article with this exact name. ... Subfamily Drosophilinae Steganinae Wikispecies has information related to: Drosophilidae Drosophilidae is a diverse, cosmopolitan family of flies, including the genus Drosophila, which includes fruit flies, vinegar flies, wine flies, pomace flies, grape flies, and picked fruit-flies. ...

Contents

Physiology

In mammals and birds the measurement of eye movement during sleep is used to divide sleep into two broad types:

  • rapid eye movement (REM) and
  • non-rapid eye movement (NREM) sleep.

Each type has a distinct set of associated physiological, neurological and psychological features. Rapid eye movement (REM) sleep is the normal stage of sleep characterized by rapid movements of the eyes. ... The sleep stages 1 through 4 are collectively referred to as NREM (non-rapid eye movement) sleep. ...


Sleep proceeds in cycles of REM and the four stages of NREM, the order normally being:

stages 1 > 2 > 3 > 4 > 3 > 2 > REM.

In humans this cycle is on average 90 to 110 minutes,[2] with a greater amount of stages 3 and 4 early in the night and more REM later in the night. Each phase may have a distinct physiological function.


Drugs such as sleeping pills and alcoholic beverages can suppress certain stages of sleep (see Sleep deprivation). This can result in a sleep that exhibits loss of consciousness but does not fulfill its physiological functions. A sedative is a drug that depresses the central nervous system (CNS), which causes calmness, relaxation, reduction of anxiety, sleepiness, slowed breathing, slurred speech, staggering gait, poor judgment, and slow, uncertain reflexes. ... Alcoholic beverages An alcoholic beverage is a drink containing ethanol, commonly known as alcohol, although in chemistry the definition of alcohol includes many other compounds. ... Sleep deprivation is a general lack of the necessary amount of sleep. ...


Rechtschaffen and Kales originally outlined the criteria for staging sleep in 1968. The American Academy of Sleep Medicine (AASM) updated the staging rules in 2007.

Stage 4 Sleep. EEG highlighted by red box.
REM Sleep. EEG highlighted by red box. Eye movements highlighted by red line.
REM Sleep. EEG highlighted by red box. Eye movements highlighted by red line.

Image File history File links Download high resolution version (837x587, 235 KB) Summary This is a screen shot of a patient during Slow Wave Sleep (stage 4). ... Image File history File links Download high resolution version (837x587, 235 KB) Summary This is a screen shot of a patient during Slow Wave Sleep (stage 4). ... Image File history File links Download high resolution version (821x601, 999 KB) Summary This is a screenshot of a polysomnographic record representing Rapid Eye Movement Sleep. ... Image File history File links Download high resolution version (821x601, 999 KB) Summary This is a screenshot of a polysomnographic record representing Rapid Eye Movement Sleep. ...

Stages of sleep

Criteria for REM sleep include not only rapid eye movements but also a rapid low voltage EEG. In mammals, at least, low muscle tone is also seen. Most memorable dreaming occurs in this stage. EEG can mean: Electroencephalography - the method and science of recording and interpreting traces of brain electrical activity as recorded from the skull surface or the device used to record such traces Emperor Entertainment Group - A Hong Kong entertainment company. ...


NREM accounts for 75–80% of total sleep time in normal human adults. In NREM sleep, there is relatively little dreaming. Non-REM encompasses four stages; stages 1 and 2 are considered 'light sleep', and 3 and 4 'deep sleep' or slow-wave sleep, SWS. They are differentiated solely using EEG, unlike REM sleep which is characterized by rapid eye movements and relative absence of muscle tone. In non-REM sleep there are often limb movements, and parasomnias such as sleepwalking may occur. Polysomnogram demonstrating SWS. High amplitude EEG is highlighted in red. ... A parasomnia is any sleep disorder such as sleepwalking, sleepeating, sleep sex, teeth grinding, night terrors, rhythmic movement disorder, REM behaviour disorder, restless leg syndrome, and somniloquy (or sleep talking), characterized by partial arousals during sleep or during transitions between wakefulness and sleep. ... Sleepwalking (also called somnambulism or noctambulism[1]), under the larger category of parasomnias or sleep disorders where the sufferer engages in activities that are normally associated with wakefulness while he or she is asleep or in a sleeplike state. ...


A cyclical alternating pattern may sometimes be observed during a stage. Cyclical Alternating Pattern occurs in sleep. ...


NREM consists of four stages according to the 2007 AASM standards:

  • During Stage N1 the brain transitions from alpha waves (common to people who are awake and having a frequency of 8 to 13 Hz) to theta waves (frequency of 4 to 7 Hz). This stage is sometimes referred to as somnolence, or "drowsy sleep". Associated with the onset of sleep during N1 may be sudden twitches and hypnic jerks. Some people may also experience hypnagogic hallucinations during this stage, which can be more troublesome to the subject. During N1 the subject loses some muscle tone, and conscious awareness of the external environment.
  • Stage N2, is characterized by "sleep spindles" (12 to 16 Hz) and "K-complexes." During this stage, muscular activity as measured by electromyography (EMG) lowers and conscious awareness of the external environment disappears. This stage occupies 45 to 55% of total sleep.
  • In Stage N3, the delta waves, also called delta rhythms (0.5 to 4 Hz) make up less than 50% of the total wave-patterns. This is considered part of deep or slow-wave sleep (SWS) and appears to function primarily as a transition into stage N4. This is the stage in which night terrors, bed wetting, sleepwalking and sleep-talking occur.
  • In Stage N4, delta-waves make up more than 50% of the wave-patterns. Stages N3 and N4 are the deepest forms of sleep; N4 is effectively a deeper version of N3, in which the deep-sleep characteristics, such as delta-waves, are more pronounced.[3]

Both REM sleep and NREM sleep stages 3 and 4 are homeostatically driven; that is, if a person or animal is selectively deprived of one of these, it rebounds once uninhibited sleep again is allowed. This suggests that both are essential to the functions of the sleep process. Alpha Waves (also known as Continuum) is an early 3D game that combines labyrinthine exploration with platform gameplay. ... This article is about the SI unit of frequency. ... Theta waves Theta rhythms are one of several characteristic electroencephalogram waveforms associated with various sleep and wakefulness states. ... A hypnic or hypnagogic jerk is an involuntary muscle twitch (more generally known as myoclonus or a myoclonic twitch) which often occurs during the transition from wakefulness to sleep (see hypnagogia). ... Hypnogogia, also spelled Hypnagogia, is the name of an experience a person can go through when falling asleep. ... Bodybuilder showing highly developed muscle tone. ... A Sleep spindle is burst of brain activity visible on an EEG that occurs during stage 2 sleep. ... K-complex A K-complex is an EEG waveform that occurs during stage 2 sleep. ... Electromyography (EMG) is a technique for evaluating and recording physiologic properties of muscles at rest and while contracting. ... A delta wave is a large, slow brain wave associated with deep sleep. ... A night terror, also known as sleep terror or pavor nocturnus, is a parasomnia sleep disorder characterized by extreme terror and a temporary inability to regain full consciousness. ... Bedwetting (or enuresis) is involuntary urination while asleep in bed. ... Sleepwalking (also called somnambulism or noctambulism[1]), under the larger category of parasomnias or sleep disorders where the sufferer engages in activities that are normally associated with wakefulness while he or she is asleep or in a sleeplike state. ... This article or section does not cite its references or sources. ...


Sleep timing

Sleep timing is controlled by the circadian clock, an inner time-keeping, temperature-fluctuating, enzyme-controlling device, and by homeostasis. A circadian rhythm is a roughly-24-hour cycle in the physiological processes of living beings, including plants, animals, fungi and cyanobacteria. ... Homeostasis (from Greek: ὅμος, homos, equal; and ιστημι, histemi, to stand lit. ...


The circadian clock works in tandem with adenosine, a neurotransmitter which inhibits many of the bodily processes that are associated with wakefulness. Adenosine is created over the course of the day; high levels of adenosine lead to sleepiness. In diurnal animals, sleepiness occurs as the circadian element causes the release of the hormone melatonin and a gradual decrease in core body temperature. The timing is affected by one's chronotype. It is the circadian rhythm which determines the ideal timing of a correctly structured and restorative sleep episode.[4] Adenosine is a nucleoside composed of adenine attached to a ribose (ribofuranose) moiety via a β-N9-glycosidic bond. ... Melatonin, 5-methoxy-N-acetyltryptamine, is a hormone found in all living creatures from algae[1] to humans, at levels that vary in a diurnal cycle. ... Chronotype is an attribute of human beings reflecting whether they are alert and prefer to be active early or late in the day. ...


Homeostatic sleep propensity, the need for sleep as a function of the amount of time elapsed since the last adequate sleep episode, is also important and must be balanced against the circadian element for satisfactory sleep. Along with corresponding messages from the circadian clock, this tells the body it needs to sleep.[5]


Sleep offset, awakening, is primarily determined by circadian rhythm. A normal person who regularly awakens at an early hour, will generally not be able to sleep in many hours later, even if moderately sleep deprived. People with some circadian rhythm sleep disorders are an exception. Circadian rhythm sleep disorders are a family of sleep disorders affecting the timing of sleep. ...


Optimal amount in humans

Adults

The optimal amount of sleep is not a meaningful concept unless the timing of that sleep is seen in relation to an individual's circadian rhythms. A person's major sleep episode is relatively inefficient and inadequate when it occurs at the "wrong" time of day. The timing is correct when the following two circadian markers occur after the middle of the sleep episode but before awakening:[6] A circadian rhythm is a roughly-24-hour cycle in the physiological processes of living beings, including plants, animals, fungi and cyanobacteria. ...

  • maximum concentration of the hormone melatonin, and
  • minimum core body temperature.

The National Sleep Foundation in the United States maintains that eight to nine hours of sleep for adult humans is optimal and that sufficient sleep benefits alertness, memory and problem solving, and overall health, as well as reducing the risk of accidents.[7] A widely publicized 2003 study[8] performed at the University of Pennsylvania School of Medicine demonstrated that cognitive performance declines with fewer than eight hours of sleep. As part of its consumer awareness programs, NSF sponsors such initiatives as National Sleep Research Fellowships provide young researchers with funds to carry on full-time research in sleep-related fields. ... The University of Pennsylvanias School of Medicine, presently located in the University City section of Philadelphia, Pennsylvania, was the countrys first school of medicine, founded at the College of Philadelphia, as the University was then called. ...


A University of California, San Diego psychiatry study of more than one million adults found that people who live the longest self-report sleeping for six to seven hours each night.[9] However, this study cannot be used to determine optimal sleep habits, only correlation — and empirically observed correlation is a necessary but not sufficient condition for causality. A need for nine or ten hours sleep a day may or may not have the same cause as the shortened life span; long sleeping itself has not been shown to be a cause of early death. The University of California, San Diego (popularly known as UCSD, or sometimes UC San Diego) is a highly selective, research-oriented[1] public university located in La Jolla, a seaside resort community of San Diego, California. ... Correlation does not imply causation is a phrase used in the sciences and statistics to emphasize that correlation between two variables does not imply there is a cause-and-effect relationship between the two. ...


Researchers from the University of Warwick and University College London have found that lack of sleep can more than double the risk of death from cardiovascular disease, but that too much sleep can also double the risk of death.[10][11] Professor Francesco Cappuccio said: “Short sleep has been shown to be a risk factor for weight gain, hypertension and Type 2 diabetes sometimes leading to mortality but in contrast to the short sleep-mortality association it appears that no potential mechanisms by which long sleep could be associated with increased mortality have yet been investigated. Some candidate causes for this include depression, low socioeconomic status and cancer-related fatigue.” “In terms of prevention, our findings indicate that consistently sleeping around 7 hours per night is optimal for health and a sustained reduction may predispose to ill-health.” The University of Warwick is a British campus university located on the outskirts of Coventry, West Midlands, England. ... Affiliations University of London Russell Group LERU EUA ACU Golden Triangle G5 Website http://www. ... Cardiovascular disease refers to the class of diseases that involve the heart or blood vessels (arteries and veins). ... For other forms of hypertension, see Hypertension (disambiguation). ...


Studies show that "sleeping more than 7 to 8 hours per day has been consistently associated with increased mortality"[12] as does short sleep duration.[13] Causal links are currently speculative: the available data may only reflect comorbid depression, socioeconomic status, or even alcohol use.[14]


Hours by age

A child sleeping
A child sleeping
A Koli Wada woman sleeping in Nirona village
A Koli Wada woman sleeping in Nirona village

Children need a greater amount of sleep per day than adults to develop and function properly: up to 18 hours for newborn babies, with a declining rate as a child ages.[7][15] A newborn baby spends almost half of its time asleep in REM-sleep. By the age of five or so, only a bit over two hours are spent in REM.[16] Image File history File linksMetadata Size of this preview: 800 × 600 pixelsFull resolution (2592 × 1944 pixel, file size: 1. ... Image File history File linksMetadata Size of this preview: 800 × 600 pixelsFull resolution (2592 × 1944 pixel, file size: 1. ... A human infant The word Infant derives from the Latin in-fans, meaning unable to speak. ...

Age Average amount of sleep per day
Newborn up to 18 hours
1-12 months 14–18 hours
1-3 years 12-15 hours
3-5 years 11-13 hours
5-12 years 9-11 hours
Adolescents 9-10 hours
Adults, including elderly 7-8 (+) hours
Pregnant women 8 (+) hours

Sleep debt

Main article: Sleep debt

Sleep debt is the effect of not getting enough rest and sleep; a large debt causes mental and physical fatigue. Scientists do not agree on how much sleep debt it is possible to accumulate, nor on whether the prevalence of sleep debt among adults has changed appreciably in the industrialized world in recent decades. It is likely that children are sleeping less than they used to in western societies.[17] This does not cite its references or sources. ...


Functions

The multiple theories proposed to explain the function of sleep are reflective of the as yet incomplete understanding of the subject.


It is likely that sleep evolved to fulfill some primeval function, but has taken over multiple functions over time as organisms have evolved. An analogy would be that of the larynx, which performs multiple functions such as controlling the passage of food and air, phonation for communicating and social purposes etc. All of these are its functions but just one of them likely represents the original function. Some of the many proposed functions of sleep are as follows:


Restoration

Wound healing has been shown to be affected by sleep. A study conducted by Gumustekin et al.[18] in 2004 shows sleep deprivation hindering the healing of burns on rats. Wound healing, or wound repair, is the bodys natural process of regenerating dermal and epidermal tissue. ... For the Todd Rundgren album, see Healing (Todd Rundgren). ...


It’s also been shown that sleep deprivation affects the immune system and metabolism. In a study by Zager et al in 2007,[19] rats were deprived of sleep for 24 hours. When compared with a control group, the sleep-deprived rats' blood tests indicated a 20% decrease in white blood cell count, a significant change in the immune system. A scanning electron microscope image of a single neutrophil (yellow), engulfing anthrax bacteria (orange). ... Structure of the coenzyme adenosine triphosphate, a central intermediate in energy metabolism. ...


A study by Bonnet and Arand[20] in 2003 indicates that sleep affects metabolism. Comparing normal human sleepers and sleepers with a form of insomnia called sleep state misperception, the researchers found significantly greater metabolism values for the normal sleepers. This article is about the sleeping disorder. ...


It has yet to be clearly proven that sleep duration affects somatic growth. One study by Jenni et al[21] in 2007 recorded growth, height and weight, as correlated to parent-reported time-in-bed in 305 children over a period of nine years (age 1-10). It was found that "the variation of sleep duration among children does not seem to have an effect on growth". It has been shown that sleep, more specifically slow-wave sleep (SWS), does affect growth hormone levels in adult men. During eight hours sleep, Van Cauter, Leproult, and Plat[22] found that the men with a high percentage of SWS (average 24%) also had high growth hormone secretion, while subjects with a low percentage of SWS (average 9%) had low growth hormone secretion. The term somatic refers to the body, as distinct from some other entity, such as the mind. ... Growth hormone (GH) or somatotropin (STH) is a protein hormone which stimulates growth and cell reproduction in humans and other animals. ...


There are multiple arguments supporting the restorative function of sleep. We feel rested after sleeping, and it is natural to assume that this is a basic purpose of sleep. Overall metabolic rate goes down during sleep and certain anabolic hormones such as growth hormones as mentioned above are secreted preferentially during sleep. Sleep among species is, in general, inversely related to the animal size and basal metabolic rate. Rats with a very high basal metabolic rate sleep for up to 14 hours a day whereas elephants and giraffes with lower BMRs sleep only 3-4 hours per day. Basal metabolic rate (BMR) is the amount of energy expended while at rest in a neutrally temperate environment, in the post-absorptive state (meaning that the digestive system is inactive, which requires about twelve hours of fasting in humans). ...


Energy conservation could as well have been accomplished by resting quiescent without shutting off the organism from the environment, potentially a dangerous situation. A sedentary non-sleeping animal is more likely to survive predators, while still preserving energy. Sleep therefore does something else other than conserving energy. Most interestingly, hibernating animals, when they wake up from hibernation go into rebound sleep because of lack of sleep during the hibernation period. They are definitely well rested and are conserving energy during hibernation, but need sleep for something else.[23] One study that was conducted kept rats awake indefinitely. They started dying after 5 days. This article refers to the process of hibernation in biology. ...


Anabolic/catabolic

Non-REM sleep may be an anabolic state marked by physiological processes of growth and rejuvenation of the organism's immune, nervous, muscular, and skeletal systems (but see above). Wakefulness may perhaps be viewed as a cyclical, temporary, hyperactive catabolic state during which the organism acquires nourishment and procreates. This article or section does not cite any references or sources. ... Anabolism is the metabolic process that builds larger molecules from smaller ones. ... Anabolism is the aspect of metabolism that contributes to growth. ...


Ontogenesis

According to the ontogenetic hypothesis of REM sleep, the activity occurring during neonatal REM sleep (or active sleep) seems to be particularly important to the developing organism (Marks et al., 1995). Studies investigating the effects of deprivation of active sleep have shown that deprivation early in life can result in behavioral problems, permanent sleep disruption, decreased brain mass (Mirmiran et al. 1983), and an abnormal amount of neuronal cell death (Morrissey, Duntley & Anch, 2004). Ontogeny (also ontogenesis or morphogenesis) describes the origin and the development of an organism from the fertilized egg to its mature form. ...


REM sleep appears to be important for development of the brain. REM sleep occupies majority of time of sleep of infants, which spend most of their time sleeping. Among different species, the more immature the baby is born, the more time it spends in REM sleep. Proponents also suggest that REM-induced muscle inhibition in the presence of brain activation exists to allow for brain development by activating the synapses yet without any motor consequences which may get the infant in trouble. Additionally, REM deprivation results in developmental abnormalities later in life.


However, this does not explain why older adults still need REM sleep, and why the fraction of time spent does not change significantly as one ages. Aquatic mammal infants do not have REM sleep in infancy. REM sleep in those animals increases as they age. Obviously, REM sleep is not needed for development in these animals.


Memory processing

Scientists have shown numerous ways in which sleep is related to memory. In a study conducted by Turner, Drummond, Salamat, and Brown[24] working memory was shown to be affected by sleep deprivation. Working memory is important because it keeps information active for further processing and supports higher-level cognitive functions such as decision making, reasoning, and episodic memory. Turner et al. allowed 18 women and 22 men to sleep only 26 minutes per night over a 4-day period. Subjects were given initial cognitive tests while well rested and then tested again twice a day during the 4 days of sleep deprivation. On the final test the average working memory span of the sleep deprived group had dropped by 38% in comparison to the control group. This demonstrates that there is clearly a connection between sleep and memory. Image File history File links Broom_icon. ... For other uses, see Memory (disambiguation). ... Working memory is a theoretical framework within cognitive psychology that refers to the structures and processes used for temporarily storing and manipulating information. ... The cognitive functions, sometimes known as mental functions, are thinking, feeling, sensing and intuition. ... Decision making is the cognitive process of selecting a course of action from among multiple alternatives. ... Reasoning is the mental (cognitive) process of looking for reasons to support beliefs, conclusions, actions or feelings. ... Episodic memory, or autobiographical memory, a sub-category of declarative memory, is the recollection of events. ...


Memory also seems to be affected differently by certain stages of sleep such as REM and slow-wave sleep (SWS). In one study cited in Born, Rasch, and Gais[25] multiple groups of human subjects were used: wake control groups and sleep test groups. Sleep and wake groups were taught a task and then tested on it both on early and late nights, with the order of nights balanced across participants. When the subject’s brains were scanned during sleep, hypnograms revealed that SWS was the dominant sleep stage during the early night representing around 23% on average for sleep stage activity. The early night test group performed 16% better on the declarative memory test than the control group. During late night sleep, REM became the most active sleep stage at about 24%, and the late night test group performed 25% better on the procedural memory test than the control group. This indicates that procedural memory benefits from late REM-rich sleep where as declarative memory benefits from early SWS-rich sleep. It has been suggested that Explicit_memory be merged into this article or section. ... Procedural memory, also known as implicit memory, is the long-term memory of skills and procedures, or how to knowledge. ...


Another study conducted by Datta[26] indirectly supports these results. The subjects chosen were 22 male rats. A box was constructed where a single rat could move freely from one end to the other. The bottom of the box was made of a steel grate. A light would shine in the box accompanied by a sound. After a 5 second delay an electrical shock would be applied. Once the shock commenced the rat could move to the other end of the box, ending the shock immediately. The rat could also use the 5 second delay to move to the other end of the box and avoid the shock entirely. The length of the shock never exceeded 5 seconds. This was repeated 30 times for half the rats. The other half, the control group, was placed in the same trial but the rats were shocked regardless of their reaction. After each of the training sessions the rat would be placed in a recording cage for 6 hours of polygraphic recordings. This process was repeated for 3 consecutive days. This study found that during the post-trial sleep recording session rats spent 25.47% more time in REM sleep after learning trials than after control trials. These trials support the results of the Born et al. study, indicating an obvious correlation between REM sleep and procedural knowledge. Procedural knowledge or know-how is the knowledge of how to perform some task. ...


Another interesting observation of the Datta study is that the learning group spent 180% more time in SWS than did the control group during the post-trial sleep-recording session. This phenomenon is supported by a study performed by Kudrimoti, Barnes, and McNaughton.[27] This study shows that after spatial exploration activity, patterns of hippocampal place cells are reactivated during SWS following the experiment. In a study by Kudrimoti et al seven rats were run through a linear track using rewards on either end. The rats would then be placed in the track for 30 minutes to allow them to adjust (PRE), then they ran the track with reward based training for 30 minutes (RUN), and then they were allowed to rest for 30 minutes. During each of these three periods EEG data was collected for information on the rats’ sleep stages. Kudrimoti et al computed the mean firing rates of hippocampal place cells during pre-behavior SWS (PRE) and three 10 min intervals in post-behavior SWS (POST) by averaging across 22 track-running sessions from seven rats. The results showed that 10 min after the trial RUN session there was a 12% increase in the mean firing rate of hippocampal place cells from the PRE level, however after 20 minutes the mean firing rate returned rapidly toward the PRE level. The elevated firing of hippocampal place cells during SWS after spatial exploration could explain why there were elevated levels of SWS sleep in Datta’s study as it also dealt with a form of spatial exploration.


The different studies all suggest that there is a correlation between sleep and the many complex functions of memory.


Preservation

The "Preservation and Protection" theory holds that sleep serves an adaptive function. It protects the person during that portion of the 24-hour day in which being awake, and hence roaming around, would place the individual at greatest risk. Organisms do not require 24 hours to feed themselves and meet other necessities. From this perspective of adaptation, organisms are safer by staying out of harm's way where potentially they could be prey to other, stronger organisms. They sleep at times that maximize their safety, given their physical capacities and their habitats. (Allison & Cicchetti, 1976; Webb, 1982).


However, this theory fails to explain why the brain disengages from the external environment during normal sleep. Another argument against the theory is that sleep is not simply a passive consequence of removing the animal from the environment, but is a "drive": animals alter their behaviors in order to obtain sleep. Therefore, circadian regulation is more than sufficient to explain periods of activity and quiescence that are adaptive to an organism, but the more peculiar specializations of sleep probably serve different and unknown functions.


Moreover, the preservation theory does not explain why carnivores like lions, which are on top of the food chain, sleep the most. By the preservation logic, these top carnivores should not need any sleep at all. Preservation does not explain why aquatic mammals sleep while moving. Lethargy during these vulnerable hours would do the same, and will be more advantageous because the animal will be quiescent but still be able to respond to environmental challenges like predators etc. Sleep rebound that occurs after a sleepless night will be maladaptive, but still occurs for a reason. For example, a zebra falling asleep the day after it spent the sleeping time running from a lion is more and not less vulnerable to predation.


Dreaming

Main article: Dream

Dreaming is the perception of sensory images during sleep, in a sequence which the sleeper/dreamer usually perceives more as an apparent participant than an observer. Dreaming is stimulated by the pons and mostly occurs during the REM phase of sleep. For other uses, see Dream (disambiguation). ... For other uses, see Pons (disambiguation). ... Rapid eye movement (REM) sleep is the normal stage of sleep characterized by rapid movements of the eyes. ...


People have proposed many hypotheses about the functions of dreaming. Sigmund Freud postulated that dreams are the symbolic expression of frustrated desires that had been relegated to the subconscious, and he used dream interpretation in the form of psychoanalysis to uncover these desires. Scientists have become skeptical about the Freudian interpretation, and place more emphasis on dreaming as a requirement for organization and consolidation of recent memory and experience. See Freud:The Interpretation of Dreams Look up Hypothesis in Wiktionary, the free dictionary. ... Sigmund Freud (IPA: ), born Sigismund Schlomo Freud (May 6, 1856 – September 23, 1939), was an Austrian neurologist and psychiatrist who founded the psychoanalytic school of psychology. ... See also: Unconscious mind. ... Dream interpretation is the process of assigning meaning to dreams. ... Today psychoanalysis comprises several interlocking theories concerning the functioning of the mind. ... For other uses, see Memory (disambiguation). ... A modern English edition of The Interpretation of Dreams. ...


Rosalind Cartwright stated that -"One Function of dreams may be to restore our sense of competence...it is also probable that in many times of stress, dreams have more work to do in resolving our problems and are thus more salient and memorable."[cite this quote] She also stated that dreams are more a state of problem solving, and that has a better and fully creative point of view, because there is no logic that restrains it since the unconscious doesn't have a logic, or a precesence of time in space.


J. Allan Hobson's and Robert McCarley's activation synthesis theory proposes that dreams are caused by the random firing of neurons in the cerebral cortex during the REM period. According to the theory, the forebrain then creates a story in an attempt to reconcile and make sense of the nonsensical sensory information presented to it, hence the odd nature of many dreams.[28] Dr. J. Allan Hobson // James Allan Hobson, M.D. (June 3, 1933 – 20--) is a Harvard psychiatrist and dream researcher who grew up in Hartford Connecticut. ... Activation Synthesis Theory is a neurobiological theory of dreams, put forward by Allan Hobson and Robert McCarley in 1973, which states that dreams are a random event caused by firing of neurons in the brain. ... Random redirects here. ... Neurons (also called nerve cells) are the primary cells of the nervous system. ... For other uses, see Cortex. ... In the anatomy of vertebrates, the prosencephalon is a part of encephalon, or brain. ... Look up Story in Wiktionary, the free dictionary. ...


Effect of food and drink on sleep

Drowsiness

  • Tryptophan

The amino acid tryptophan is a building block of the protein found in foods. It contributes to sleepiness. Carbohydrates make tryptophan more available to the brain, which is why carbohydrate-heavy meals containing tryptophan tend to cause drowsiness. [1] Tryptophan (abbreviated as Trp or W)[1] is one of the 20 standard amino acids, which are the building blocks of proteins, and an essential amino acid in the human diet. ...

  • Melatonin

Melatonin is a naturally occurring hormone that regulates sleepiness. It is made in the brain where tryptophan is converted into serotonin and then into melatonin, which is released at night by the pineal gland to induce and maintain sleep. Melatonin supplementation may be used as a sleep aid. [2] The pineal gland (also called the pineal body or epiphysis) is a small endocrine gland in the brain. ...

  • The "Post-Lunch Dip"

Many people have a temporary drop in alertness in early afternoon, commonly known as the post-lunch dip. While a large meal, rich in carbohydrates, can make a person feel sleepy, the post-lunch dip is mostly an effect of the biological clock. People naturally feel most sleepy at two different times of the day: about 2:00 AM and 2:00 PM. [3] A circadian rhythm is a roughly-24-hour cycle in the physiological processes of living beings, including plants, animals, fungi and cyanobacteria. ...

  • Alcohol

Alcoholic beverages aid relaxation and commonly are used as a sleep aid. Alcohol tends, however, to disrupt sleep throughout the night and can prevent the deeper stages of sleep from occurring. [4]


Stimulation

Caffeine is a stimulant that works by slowing the action of the hormones in the brain that cause sleepiness. Effective dosage is individual, in part dependent on prior usage. It can cause a rapid reduction in alertness as it wears off. [5] For other uses, see Caffeine (disambiguation). ...

Amphetamines are often used to treat narcolepsy, the most common effects are decreased appetite, increased stamina, and physical energy. Amphetamine is a synthetic drug originally developed (and still used) as an appetite suppressant. ... For other uses, see Narcolepsy (disambiguation). ...

The stimulating effects of energy drinks comes from natural stimulants such as caffeine, sugars, and essential amino acids, and eventually will create a rapid reduction in alertness similar to that of caffeine. [6] Energy drinks are beverages which contain legal stimulants, vitamins, and minerals, including caffeine, guarana, taurine, various forms of ginseng, maltodextrin, carnitine, creatine, and ginkgo biloba. ...


Causes of difficulty in sleeping

There are a great many possible reasons for sleeping poorly. Following sleep hygienic principles may solve problems of physical or emotional discomfort.[29] When pain, illness, drugs or stress are the culprit, the cause must be treated. Sleep disorders, including the sleep apneas, narcolepsy, primary insomnia, periodic limb movement disorder (PLMD), restless leg syndrome (RLS) and the circadian rhythm sleep disorders, are treatable. Sleep hygiene is the practice of following simple guidelines in an attempt to ensure more restful, effective sleep which can promote daytime alertness and help treat or avoid certain kinds of sleep disorders. ... Sleep apnea is a sleep disorder characterized by pauses in breathing during sleep. ... For other uses, see Narcolepsy (disambiguation). ... Periodic Limb Movement Disorder (PLMD), also called nocturnal myoclonus, is a sleep disorder where the patient moves involuntarily during sleep. ... Wittmaack-Ekbom or restless legs syndrome is a disorder of the nervous system that affects sensation and movement in the legs and causes the limbs to feel uncomfortable. ... Circadian rhythm sleep disorders are a family of sleep disorders affecting the timing of sleep. ...


Elderly people may to some degree lose the ability to consolidate sleep. They need the same amount per day as they've always needed, but may need to take some of their sleep as daytime naps.


Anthropology of sleep

Recent research suggests that sleep patterns vary significantly across human cultures.[30][31] The most striking differences are between societies that have plentiful artificial light and ones that do not. Cultures without artificial light have more broken-up sleep patterns. This is called polyphasic sleep or segmented sleep and has led to expressions such as "first sleep," "watch," and "second sleep" which appear in literature from all over the world. The word culture comes from the Latin root colere (to inhabit, to cultivate, or to honor). ... Lighting includes both artificial light sources such as lamps and natural illumination of interiors from daylight. ... Polyphasic sleep is a term used to describe several alternative sleep patterns intended to reduce sleep time to 2–6 hours daily in order to achieve a better quality of sleep. ... Segmented sleep or divided sleep are modern Western terms for a polyphasic sleep pattern found in medieval and early modern Europe and many modern non-industrial societies, where the nights sleep is evenly divided by a few hours of wakefulness. ...


Some cultures have fragmented sleep patterns in which people sleep at all times of the day, and for shorter periods at night. For example, many Mediterranean and Latin American cultures have a siesta, in which people sleep for a period in the afternoon. In many nomadic or hunter-gatherer societies people sleep off and on throughout the day or night depending on what is happening.[citation needed] The Mediterranean Sea is an intercontinental sea positioned between Europe to the north, Africa to the south and Asia to the east, covering an approximate area of 2. ... Latin America consists of the countries of South America and some of North America (including Central America and some the islands of the Caribbean) whose inhabitants mostly speak Romance languages, although Native American languages are also spoken. ... A painting of a young woman taking a siesta. ... Look up Afternoon in Wiktionary, the free dictionary. ... Communities of nomadic people move from place to place, rather than settling down in one location. ... In anthropology, the hunter-gatherer way of life is that led by certain societies of the Neolithic Era based on the exploitation of wild plants and animals. ...


Some sleep deprivation-oriented sleep patterns have been experimented with involving sleeping in regular patterns of evenly spread ultra-short naps for the purpose of greatly increasing wake time per day. Such patterns purportedly lead to the body's ability to jump instantly into the most necessary sleep stages.


Since plentiful artificial light became available in some cultures in the mid-19th century, sleep patterns have changed significantly in these cultures. These people sleep in a concentrated burst at night, and sleep later in the morning.[citation needed] Alternative meaning: Nineteenth Century (periodical) (18th century — 19th century — 20th century — more centuries) As a means of recording the passage of time, the 19th century was that century which lasted from 1801-1900 in the sense of the Gregorian calendar. ...


Sleep in non-humans

Main article: Sleep (non-human)

Horses and other herbivorous ungulates can sleep while standing, but must necessarily lie down for REM sleep (which causes muscular atony) for short periods - giraffes, for example, only need to lie down for REM sleep for a few minutes at a time. Bats sleep while hanging upside down. Some aquatic mammals and some birds can sleep with one half of the brain, while the other half is awake, so called unihemispheric slow-wave sleep.[32] Birds and mammals have cycles of non-REM and REM sleep as described above for humans, though birds’ cycles are much shorter and they do not lose muscle tone, “go limp”, to the same extent that most mammals do. Image File history File linksMetadata Download high-resolution version (1024x681, 527 KB) 昼寝中のニホンザル(神庭の滝にて) File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Sleep Metadata This file contains additional information, probably added from the digital camera or scanner used to create... Image File history File linksMetadata Download high-resolution version (1024x681, 527 KB) 昼寝中のニホンザル(神庭の滝にて) File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Sleep Metadata This file contains additional information, probably added from the digital camera or scanner used to create... Binomial name Macaca fuscata Blyth, 1875 The Japanese Macaque (Macaca fuscata), also known as the Snow Monkey, is a terrestrial Old World monkey species native to northern Japan, although an introduced free-ranging population has been living near Laredo, Texas since 1972. ... Unihemispheric slow-wave sleep (USWS) is sleep in which only one half of the animal brain is at rest, with the other half alert. ...


Sleep appears to be common to the animal kingdom, but it becomes difficult to define in lower order animals. It has, however, behavioral characteristics such as minimal movement, a posture typical for the species and reduced responsiveness to external stimulation. It is quickly reversible, as opposed to hibernation or coma, and sleep deprivation is followed by longer and/or deeper sleep. For other uses, see Coma (disambiguation). ...


A study in 2005 shows that killer whales and some dolphins don't sleep during their first month of life.[7] All other mammal species that have been studied experience increased sleep after birth.[33] Binomial name Orcinus orca Linnaeus, 1758 Orca range (in blue) The orca (Orcinus orca), commonly known as the killer whale, and sometimes called the grampus, is the largest member of the oceanic dolphin family. ... For other uses, see Dolphin (disambiguation). ...


Longest period without sleep

Depending on how sleep is defined, there are several people who can claim the record for having gone the longest without sleep:

  1. Thai Ngoc, born 1942, claims to have been awake for 33 years or 11,700 nights, according to Vietnamese news organization Thanh Nien. It was said that Ngoc acquired the ability to go without sleep after a bout of fever in 1973,[34] but other reports indicate he stopped sleeping in 1976 with no known trigger.[35] At the time of the Thanh Nien report, Ngoc suffered from no apparent ill effect (other than a minor decline in liver function), was mentally sound and could carry 100 kg of pig feed down a 4 km road,[34] but another report indicates that he was healthy before the sleepless episode but that now he was not feeling well because of the lack of sleep.[35]
  2. In January 2005, the RIA Novosti published an article about Fyodor Nesterchuk from the Ukrainian town of Kamen-Kashirsky who claimed to have not slept in more than 20 years. Local doctor Fyodor Koshel, chief of the Lutsk city health department, claimed to have examined him extensively and failed to make him sleep. Koshel also said however that Nesterchuck did not suffer any of the normally deleterious effects of sleep deprivation.[8] Several bloggers have commented that people who claim not to sleep are usually shown to sleep when studied in sleep laboratories with EEG.[9] Another blog stated that Ananova's reprinting of the story is indicative of their having a reputation for not being a credible source of news.[10] The "problem" may lie in that Nesterchuck and people like him don't remember sleeping, which may be cause for further study. Whether he doesn't sleep at night or doesn't remember sleeping at night, either event indicates a condition not present in most humans. Nesterchuck reports experiencing drowsiness at night, commenting that he attempts to sleep "in vain" when he notices his eyelids drooping. Many people also experience microsleep episodes during sleep deprivation, in which they sleep for periods of seconds to fractions of a second and frequently don't remember these episodes. Because microsleep is frequently not remembered, microsleep or a related phenomenon may be responsible for lack of sleep and/or lack of memory in individuals like Nesterchuk and Thai Ngoc.
  3. Randy Gardner holds the Guinness World Record for intentionally having gone the longest without sleep. In 1965, Gardner, then 18, stayed awake for 264 hours (about 11 days) for a high school science project.[36] He experienced significant deficits in concentration, motivation, perception and other higher mental processes during his sleep deprivation. However, he recovered normal cognitive functions after a few nights' sleep.
  4. On May 25, 2007 the BBC reported that Tony Wright beat the Guinness World Record by staying awake for 11 days and nights.[37] The Guinness Book of Records has, however, withdrawn its backing of a sleep deprivation class because of the associated health risks.

Thai Ngoc (born 1942) is a Vietnamese insomniac. ... Georges River, in the southern suburbs of Sydney (Australia) is a ria, or drowned river valley. ... Lutsk (Ukrainian: Луцьк) is the capital of the Volyn Oblast, Ukraine. ... Ananova is a Web-oriented news service that features a computer-simulated animation of a woman newscaster, named Ananova, who has been programmed to read newscasts to Web users. ... A microsleep is a period of sleep lasting no more than a few seconds up to a minute. ... Randy Gardner holds a Guinness world record for the longest period of time a human being has intentionally gone without sleep not using stimulants of any kind. ... Guinness World Records 2008 edition. ... is the 145th day of the year (146th in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) was a common year starting on Monday of the Gregorian calendar in the 21st century. ...

See also

Common sleeping positions, practices, and rituals

Co-sleeping, also called the family bed, is a practice in which babies and young children sleep with one or both parents. ... For other uses, see Hypnotized (song). ... For other senses of this word, see Meditation (disambiguation). ... Sleep hygiene is the practice of following simple guidelines in an attempt to ensure more restful, effective sleep which can promote daytime alertness and help treat or avoid certain kinds of sleep disorders. ... This article or section does not cite any references or sources. ...

Other

7 days 6 hours 52 minutes and 12 seconds A microsleep is a period of sleep lasting no more than a few seconds up to a minute. ... Morvans syndrome (or fibrillary chorea) is a rare disease named after nineteenth century French physician Augustin Marie Morvan (1819-1897). ... A basic digital clock radio with analog tuning A wind-up, spring-driven alarm clock An alarm clock is a clock that is designed to make an alert sound at a specific date and/or time. ... Dream worlds are a commonly used plot device in fictional works, most notably in science fiction and fantasy fiction. ...


References

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  37. ^ BBC NEWS | England | Cornwall | Man claims new sleepless record

2008 (MMVIII) is the current year, a leap year that started on Tuesday of the Anno Domini (or common era), in accordance to the Gregorian calendar. ... is the 25th day of the year in the Gregorian calendar. ... 2008 (MMVIII) is the current year, a leap year that started on Tuesday of the Anno Domini (or common era), in accordance to the Gregorian calendar. ... is the 41st day of the year in the Gregorian calendar. ... Year 2007 (MMVII) was a common year starting on Monday of the Gregorian calendar in the 21st century. ... is the 176th day of the year (177th in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) was a common year starting on Monday of the Gregorian calendar in the 21st century. ... is the 329th day of the year (330th in leap years) in the Gregorian calendar. ... 2008 (MMVIII) is the current year, a leap year that started on Tuesday of the Anno Domini (or common era), in accordance to the Gregorian calendar. ... is the 25th day of the year in the Gregorian calendar. ... Year 2007 (MMVII) was a common year starting on Monday of the Gregorian calendar in the 21st century. ... is the 329th day of the year (330th in leap years) in the Gregorian calendar. ... Also see: 2002 (number). ... is the 46th day of the year in the Gregorian calendar. ... Year 2007 (MMVII) was a common year starting on Monday of the Gregorian calendar in the 21st century. ... is the 112th day of the year (113th in leap years) in the Gregorian calendar. ... 2008 (MMVIII) is the current year, a leap year that started on Tuesday of the Anno Domini (or common era), in accordance to the Gregorian calendar. ... is the 25th day of the year in the Gregorian calendar. ... 2008 (MMVIII) is the current year, a leap year that started on Tuesday of the Anno Domini (or common era), in accordance to the Gregorian calendar. ... is the 25th day of the year in the Gregorian calendar. ... 2008 (MMVIII) is the current year, a leap year that started on Tuesday of the Anno Domini (or common era), in accordance to the Gregorian calendar. ... is the 13th day of the year in the Gregorian calendar. ... Year 2007 (MMVII) was a common year starting on Monday of the Gregorian calendar in the 21st century. ... is the 1st day of the year in the Gregorian calendar. ... 2008 (MMVIII) is the current year, a leap year that started on Tuesday of the Anno Domini (or common era), in accordance to the Gregorian calendar. ... is the 25th day of the year in the Gregorian calendar. ... A digital object identifier (or DOI) is a standard for persistently identifying a piece of intellectual property on a digital network and associating it with related data, the metadata, in a structured extensible way. ... Year 2007 (MMVII) was a common year starting on Monday of the Gregorian calendar in the 21st century. ... is the 87th day of the year (88th in leap years) in the Gregorian calendar. ... Year 2000 (MM) was a leap year starting on Saturday. ... is the 213th day of the year (214th in leap years) in the Gregorian calendar. ... 2008 (MMVIII) is the current year, a leap year that started on Tuesday of the Anno Domini (or common era), in accordance to the Gregorian calendar. ... is the 25th day of the year in the Gregorian calendar. ... Year 2006 (MMVI) was a common year starting on Sunday of the Gregorian calendar. ... is the 45th day of the year in the Gregorian calendar. ... Year 2007 (MMVII) was a common year starting on Monday of the Gregorian calendar in the 21st century. ... is the 106th day of the year (107th in leap years) in the Gregorian calendar. ... Also see: 2002 (number). ... is the 84th day of the year (85th in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) was a common year starting on Monday of the Gregorian calendar in the 21st century. ... is the 113th day of the year (114th in leap years) in the Gregorian calendar. ...

Further reading

  • Bar-Yam, Yaneer (2003). "Chapter 3", Dynamics of Complex Systems (PDF). 
  • Foldvary-Schaefer N, Grigg-Damberger M (Feb 2006). "Sleep and epilepsy: what we know, don't know, and need to know.". J Clin Neurophysiol 23 (1): 4–20. PMID 16514348. 
  • Gilmartin G, Thomas R (Nov 2004). "Mechanisms of arousal from sleep and their consequences.". Curr Opin Pulm Med 10 (6): 468-74. PMID 15510052.  [Review]
  • Gottlieb D, Punjabi N, Newman A, Resnick H, Redline S, Baldwin C, Nieto F (Apr 25 2005). "Association of sleep time with diabetes mellitus and impaired glucose tolerance.". Arch Intern Med 165 (8): 863-7. PMID 15851636. 
  • Legramante J, Galante A (Aug 9 2005). "Sleep and hypertension: a challenge for the autonomic regulation of the cardiovascular system.". Circulation 112 (6): 786-8. PMID 16087808.  [Editorial]
  • Feinberg I. Changes in sleep cycle patterns with age J Psychiatr Res. 1974;10:283–306. [review]
  • Tamar Shochat and Sonia Ancoli - Specific Clinical Patterns in Aging - Sleep and Sleep Disorders [website]
  • Zepelin H. Normal age related changes in sleep. In: Chase M, Weitzman ED, eds. Sleep Disorders: Basic and Clinical Research. New York: SP Medical; 1983:431–434.
  • Morrissey M, Duntley S, Anch A, Nonneman R (2004). "Active sleep and its role in the prevention of apoptosis in the developing brain.". Med Hypotheses 62 (6): 876-9. PMID 15142640. 
  • Marks G, Shaffery J, Oksenberg A, Speciale S, Roffwarg H (Jul-Aug 1995). "A functional role for REM sleep in brain maturation.". Behav Brain Res 69 (1–2): 1–11. PMID 7546299. 
  • Mirmiran M, Scholtens J, van de Poll N, Uylings H, van der Gugten J, Boer G (Apr 1983). "Effects of experimental suppression of active (REM) sleep during early development upon adult brain and behavior in the rat.". Brain Res 283 (2–3): 277-86. PMID 6850353. 
  • Zhang, J. (Dec 2004). "[Memory process and the function of sleep]" (PDF). Journal of Theoretics 6 (6). 

External links

Look up Sleep in
Wiktionary, the free dictionary.
Wiktionary (a portmanteau of wiki and dictionary) is a multilingual, Web-based project to create a free content dictionary, available in over 151 languages. ... Rapid eye movement (REM) sleep is the normal stage of sleep characterized by rapid movements of the eyes. ... The sleep stages 1 through 4 are collectively referred to as NREM (non-rapid eye movement) sleep. ... Polysomnogram demonstrating SWS. High amplitude EEG is highlighted in red. ... Beta waves Beta wave, or beta rhythm, is the term used to designate the frequency range of brain activity above 12 Hz (12 transitions or cycles per second). ... A delta wave is a large, slow brain wave associated with deep sleep. ... Gamma waves A gamma wave is a pattern of brain waves, associated with perception and consciousness. ... In humans, a theta wave is an electroencephalogram pattern normally produced while awake but relaxed or drowsy. ... Advanced sleep phase syndrome (ASPS) is a sleep disorder in which patients feel very sleepy early in the evening (e. ... Automatism, from the Greek automatismos or self action, is the spontaneous production of often purposeless verbal or motor behavior without conscious self-control, self-conceptualization or self-censorship. ... Circadian rhythm sleep disorders are a family of sleep disorders affecting the timing of sleep. ... Delayed sleep-phase syndrome (DSPS) is a chronic disorder of sleep timing. ... Dyssomnias are a broad classification of sleeping disorder that make it difficult to get to sleep, or to stay sleeping. ... Hypersomnia, also known as excessive daytime sleepiness (EDS), is excessive amount of sleepiness. ... Hypersomnia, also known as excessive daytime sleepiness (EDS), is excessive amount of sleepiness. ... This article is about the sleeping disorder. ... For other uses, see Narcolepsy (disambiguation). ... For other uses, see Night Terror. ... Nocturia is the need to get up during the night in order to urinate, thus interrupting sleep. ... Periodic Limb Movement Disorder (PLMD), also called nocturnal myoclonus, is a sleep disorder where the patient moves involuntarily during sleep. ... Non 24-hour sleep phase syndrome, also termed non 24-hour circadian rhythm disorder or hypernychthemeral syndrome, is a sleep disorder in which a persons internal clock runs longer than 24 hours. ... Ondines Curse, also called congenital central hypoventilation syndrome (CCHS) or primary alveolar hypoventilation, is a respiratory disorder that is fatal if untreated. ... A parasomnia is any sleep disorder such as sleepwalking, sleepeating, sleep sex, teeth grinding, night terrors, rhythmic movement disorder, REM behaviour disorder, restless leg syndrome, and somniloquy (or sleep talking), characterized by partial arousals during sleep or during transitions between wakefulness and sleep. ... Sleep apnea is a sleep disorder characterized by pauses in breathing during sleep. ... Sleep deprivation is a general lack of the necessary amount of sleep. ... Sleepeating or Nocturnal Eating Syndrome is a parasomnia where people experience recurrent episodes of eating during their sleep, without being aware of it. ... Sleeping sickness or African trypanosomiasis is a parasitic disease in people and animals, caused by protozoa of genus Trypanosoma and transmitted by the tsetse fly. ... This article does not cite any references or sources. ... Sleepwalking (also called somnambulism or noctambulism[1]), under the larger category of parasomnias or sleep disorders where the sufferer engages in activities that are normally associated with wakefulness while he or she is asleep or in a sleeplike state. ... For other uses, see Dream (disambiguation). ... The current usage of the term nightmare refers to a dream which causes the sleeper a strong unpleasant emotional response. ... Exploding head syndrome is a condition first reported by a British physician in 1988[1] that causes the sufferer to occasionally experience a tremendously loud noise as if from within his or her own head, usually described as an explosion, roar or a ringing noise. ... Hypnos and Thanatos,Sleep and His Half-Brother Death by John William Waterhouse Wikibooks has a book on the topic of Lucid Dreaming A lucid dream, also known as a conscious dream, is a dream in which the person is aware that he or she is dreaming while the dream... A false awakening is an event in which someone dreams they have awakened from sleep. ... The Nightmare, by Henry Fuseli (1781) is thought to be one of the classic depictions of sleep paralysis perceived as a demonic visitation. ... Hypnagogia (also spelled hypnogogia) describes vivid dream-like auditory, visual, or tactile sensations, which are often accompanied by sleep paralysis and experienced when falling asleep or waking up. ... A hypnic or hypnagogic jerk is an involuntary muscle twitch (more generally known as myoclonus or a myoclonic twitch) which often occurs during the transition from wakefulness to sleep (see hypnagogia). ... A nocturnal emission is an ejaculation of semen experienced by a male during sleep. ... Somnolence (or drowsiness) is a state of near-sleep, a strong desire for sleep, or sleeping for unusually long periods. ... Dream worlds are a commonly used plot device in fictional works, most notably in science fiction and fantasy fiction. ... Bedding refers to the materials laid above the mattress of a bed for warmth. ... This article is about the cushion. ... A bed sheet is a large piece of cotton or linen cloth used to cover a mattress. ... A double duvet. ... For other uses, see Blanket (disambiguation). ... A quilt is a type of puppy with long fluffy ears. ... A sleeping bag is a protective bag for a person to sleep in, essentially a blanket that can be closed with a zipper or similar means, and functions as a bed in situations where it is impractical to carry around a full bed. ... Nightwear, also called sleepwear, nightclothes, or nightdress, is clothing designed to be worn while sleeping. ... This article or section does not cite its references or sources. ... A child wearing a blanket sleeper. ... Fashionable young men in early 16th century Germany showed a lot of fine linen in a studied negligence. ... The negligee is a form of womenswear intended for wear at night and in the bedroom or in a airport parking lot. ... Pink chiffon nightie A nightgown (also called a nightdress) is a loosely hanging item of nightwear nowadays solely for women, Its length may vary from hip-length (babydoll) to floor-length (peignoir) but is typically knee-length. ... This article does not cite any references or sources. ... For other uses, see Nightcap (disambiguation). ... A peignoir is a long nightgown for women usually sheer and made of chiffon. ... Look up Pajamas in Wiktionary, the free dictionary. ... Short pink chiffon nightgown Black slip nightgown A nightgown (also called a nightdress) is a loosely hanging item of nightwear nowadays mostly for women. ... For other uses, see Bed (disambiguation). ... A Bunkbed A bunk bed is a type of bed in which one bed is stacked on top of another. ... A four poster bed is a bed with four posts which support a tester. ... A futon in Japan A futon in the U.S. A futon )   is a type of mattress that makes up a Japanese bed. ... Garden hammock A couple in a hammock on the beach The hammock is a fabric sling used for sleeping or resting. ... A pillow top queen-size mattress. ... Genera & Species Genus Cimex Cimex lectularius Cimex hemipterus () Cimex pilosellus Cimex pipistrella Genus Leptocimex Leptocimex boueti Genus Haematosiphon Haematosiphon inodora Genus Oeciacus Oeciacus hirudinis Oeciacus vicarius Genus Afrocimex Afrocimex constrictus A bedbug (or bed bug) is a small nocturnal insect of the family Cimicidae that lives by hematophagy, that is... A bedroom is a room where people sleep. ... Bedtime is a popular parenting tradition that involves, to a greater or lesser extent, rituals made to help children feel more secure [1], and become accustomed to a comparatively more rigid schedule of sleep than they would sometimes prefer. ... Bedtime Stories track listing GHV2 track listing For the 1964 comedy film, see Bedtime Story (film). ... Chronotype is an attribute of human beings reflecting whether they are alert and prefer to be active early or late in the day. ... Jet lag (or jet-lag) is a physical condition caused by crossing multiple time zones during flight. ... For other uses, see Lullaby (disambiguation). ... Polyphasic sleep is a term used to describe several alternative sleep patterns intended to reduce sleep time to 2–6 hours daily in order to achieve a better quality of sleep. ... A power nap (sometimes called a catnap) is a short nap, usually 15-20 minutes, intended to revitalize the subject from drowsiness while working, coined by Cornell University social psychologist James Maas. ... A painting of a young woman taking a siesta. ... Many competing theories have been advanced to discover the possible connections between sleep and learning in humans. ... This does not cite its references or sources. ... Sleep inertia is a physiological state characterised by a decline in motor dexterity and a subjective feeling of grogginess, immediately following an abrupt awakening from deep sleep. ... For other uses, see Sleepover (film). ... Snoring is the act of breathing through the open mouth in such a way as to cause a vibration of the uvula and soft palate, thus giving rise to a sound which may vary from a soft noise to a loud unpleasant sound. ... This article or section does not cite its references or sources. ...

  Results from FactBites:
 
Sleep -- Encarta ® Online Deluxe (2060 words)
Sleep is distinguished from other sleeplike states, for instance, hibernation or coma, because it is easily interrupted by external stimulation, such as a loud noise.
REM sleep is generated by a region in the brainstem, called the pons, and adjacent portions of the midbrain.
Sleep may have evolved to protect animals from their predators by reducing their activity during the times when they are most vulnerable.
How Much Sleep Is Enough for My Child? (2051 words)
Sleep — or lack of it — is probably the most-discussed aspect of baby care.
The quality and quantity of an infant's sleep affects the well-being of everyone in the household — it's the difference between being cheerful, alert parents and members of the walking dead.
Most children's sleep requirements fall within a predictable range of hours based on their age, but each child is a unique individual with distinct sleep needs.
  More results at FactBites »

 
 

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