Sleep

sleepingsleep architectureasleepsleep stagessleep patternsstages of sleepsleep patternsoporificWaking uprest
Sleep is a naturally recurring state of mind and body, characterized by altered consciousness, relatively inhibited sensory activity, reduced muscle activity and inhibition of nearly all voluntary muscles during rapid eye movement (REM) sleep, and reduced interactions with surroundings.wikipedia
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Adenosine

Aadenosine analogAdenoscan
Process S is driven by the depletion of glycogen and accumulation of adenosine in the forebrain that disinhibits the ventrolateral preoptic nucleus, allowing for inhibition of the ascending reticular activating system.
Adenosine itself is a neuromodulator, believed to play a role in promoting sleep and suppressing arousal.

Endocrine system

endocrineendocrinologicalendocrine organ
During sleep, most of the body's systems are in an anabolic state, helping to restore the immune, nervous, skeletal, and muscular systems; these are vital processes that maintain mood, memory, and cognitive function, and play a large role in the function of the endocrine and immune systems.
Hormones are used to communicate between organs and tissues for physiological regulation and behavioral activities, such as digestion, metabolism, respiration, tissue function, sensory perception, sleep, excretion, lactation, stress, growth and development, movement, reproduction, and mood.

Ventrolateral preoptic nucleus

ventrolateral preoptic areaVLPOintermediate nucleus
Process S is driven by the depletion of glycogen and accumulation of adenosine in the forebrain that disinhibits the ventrolateral preoptic nucleus, allowing for inhibition of the ascending reticular activating system.
The VLPO is active during sleep, particularly during non-rapid eye movement sleep (NREM sleep), and releases inhibitory neurotransmitters, mainly GABA and galanin, which inhibit neurons of the ascending arousal system that are involved in wakefulness and arousal.

Sharp waves and ripples

Sharp wave–ripple complexessharp-wave ripplessharp waves
This dialogue between hippocampus and neocortex occurs in parallel with hippocampal sharp-wave ripples and thalamo-cortical spindles, synchrony that drives the formation of spindle-ripple event which seems to be a prerequisite for the formation of long-term memories.
Sharp waves and ripples (SWRs) are oscillatory patterns in the mammalian brain hippocampus seen on an EEG during immobility and sleep.

Electronic media and sleep

electronic media use
Blue light, in particular, exerts the strongest effect, leading to concerns that electronic media use before bed may interfere with sleep.
The use of computers (including devices such as smartphones, tablet computers and laptops) by children and adolescents before bed has been associated with a reduction in the hours of sleep experienced by frequent users, along with a decreased quality of sleep, in most cases.

Reticular formation

reticular activating systemreticulospinal tractascending reticular activating system
Process S is driven by the depletion of glycogen and accumulation of adenosine in the forebrain that disinhibits the ventrolateral preoptic nucleus, allowing for inhibition of the ascending reticular activating system.

Obstructive sleep apnea

obstructive sleep apnea syndromeobstructive sleep apnoeaobstructive sleep apnea syndrome or obstructive sleep apnea–hypopnea syndrome
Obstructive sleep apnea is a condition in which major pauses in breathing occur during sleep, disrupting the normal progression of sleep and often causing other more severe health problems.
Obstructive sleep apnea (OSA) is the most common type of sleep apnea and is characterised by repeated episodes of complete or partial obstructions of the upper airway during sleep, despite the effort to breathe, and is usually associated with a reduction in blood oxygen saturation.

Central sleep apnea

central sleep apnea syndromecentralCentral Apnea
Obstructive sleep apnea is more common than central sleep apnea.
Central sleep apnea (CSA) or central sleep apnea syndrome (CSAS) is a sleep-related disorder in which the effort to breathe is diminished or absent, typically for 10 to 30 seconds either intermittently or in cycles, and is usually associated with a reduction in blood oxygen saturation.

Nocturnal penile tumescence

morning erectionnocturnal erectionmorning erections
Counterintuitively, penile erections during sleep are not more frequent during sexual dreams than during other dreams.
Nocturnal penile tumescence is a spontaneous erection of the penis during sleep or when waking up.

Night owl (person)

night owlnight owlsevening person
Different characteristic sleep patterns, such as the familiarly so-called "early bird" and "night owl", are called chronotypes.
Some night owls with great difficulty adopting normal sleeping and waking times may have delayed sleep-phase disorder.

Restless legs syndrome

restless leg syndromerestless legsrestless legs syndrome (RLS)
Sleep disorders include narcolepsy, periodic limb movement disorder (PLMD), restless leg syndrome (RLS), upper airway resistance syndrome (UARS), and the circadian rhythm sleep disorders.
The feelings generally happen when at rest and therefore can make it hard to sleep.

Sleepwalking

somnambulismsomnambulistsleepwalker
Humans may suffer from various sleep disorders, including dyssomnias such as insomnia, hypersomnia, narcolepsy, and sleep apnea; parasomnias such as sleepwalking and REM behavior disorder; bruxism; and circadian rhythm sleep disorders.
Sleepwalking, also known as somnambulism or noctambulism, is a phenomenon of combined sleep and wakefulness.

Unconscious mind

unconsciousunconsciouslythe unconscious
Sigmund Freud postulated that dreams are the symbolic expression of frustrated desires that have been relegated to the unconscious mind, and he used dream interpretation in the form of psychoanalysis in attempting to uncover these desires.
While sleep, sleepwalking, dreaming, delirium and comas may signal the presence of unconscious processes, these processes are seen as symptoms rather than the unconscious mind itself.

Robert McCarley

McCarley
John Allan Hobson and Robert McCarley propose that dreams are caused by the random firing of neurons in the cerebral cortex during the REM period.
McClarley is a prominent researcher in the field of sleep and dreaming as well as schizophrenia.

Chronotype

diurnal variationchronotypesDiurnal variations
Different characteristic sleep patterns, such as the familiarly so-called "early bird" and "night owl", are called chronotypes.
The 20th century saw greatly increased interest in and research on all questions about sleep.

Theta wave

thetatheta rhythmtheta waves
Furthermore, nocturnal reactivation seems to share the same neural oscillatory patterns as reactivation during wakefulness, processes which might be coordinated by theta activity.
In older children and adults, it tends to appear during meditative, drowsy, hypnotic or sleeping states, but not during the deepest stages of sleep.

Sleep spindle

sleep spindlesthalamo-cortical spindlesspindle wave oscillations
This dialogue between hippocampus and neocortex occurs in parallel with hippocampal sharp-wave ripples and thalamo-cortical spindles, synchrony that drives the formation of spindle-ripple event which seems to be a prerequisite for the formation of long-term memories.
Recent research has revealed that spindles distort the transmission of auditory information to the cortex; spindles isolate the brain from external disturbances during sleep.

Biphasic and polyphasic sleep

polyphasic sleepSegmented sleepPolyphasic
In polyphasic sleep, an organism sleeps several times in a 24-hour cycle, whereas in monophasic sleep occurs all at once.
Biphasic sleep (or diphasic, bimodal or bifurcated sleep) is the practice of sleeping during two periods over the course of 24 hours, while polyphasic sleep refers to sleeping multiple times – usually more than two.

Bed

bedschambre de paradequeen-sized
Some sleep directly on the ground; others on a skin or blanket; others sleep on platforms or beds.
A bed is a piece of furniture which is used as a place to sleep or relax.

Hypnos

Somnusgod of sleepGreek God Hypnos
Sleep has been seen in culture as similar to death since antiquity; in Greek mythology, Hypnos (the god of sleep) and Thanatos (the god of death) were both said to be the children of Nyx (the goddess of night).
In Greek mythology, Hypnos (, "sleep") is the personification of sleep; the Roman equivalent is known as Somnus.

Alarm clock

clock radioalarmalarm clocks
Today, many humans wake up with an alarm clock; however, people can also reliably wake themselves up at a specific time with no need for an alarm.
Scientific studies on sleep having shown that sleep stage at awakening is an important factor in amplifying sleep inertia.

Fatal insomnia

Fatal familial insomniaInsomnia, fatal familialfamilial fatal insomnia
Fatal familial insomnia, or FFI, an extremely rare genetic disease with no known treatment or cure, is characterized by increasing insomnia as one of its symptoms; ultimately sufferers of the disease stop sleeping entirely, before dying of the disease.

Microsleep

micro-sleepmicro-sleepsMicrosleeps
A micro-sleep (MS) is a temporary episode of sleep or drowsiness which may last for a fraction of a second or up to 30 seconds where an individual fails to respond to some arbitrary sensory input and becomes unconscious.

Eszopiclone

Lunesta
Sleeping medications such as Ambien and Lunesta are an increasingly popular treatment for insomnia.

Power nap

power-nappower-napping
A power nap is a short sleep that terminates before deep sleep (slow-wave sleep; SWS); it is intended to quickly revitalize the subject.