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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Thermoregulation

body temperaturethermoregulatethermoregulatory
The circadian clock exerts constant influence on the body, effecting sinusoidal oscillation of body temperature between roughly 36.2 °C and 37.2 °C.

Melatonin

CircadinmelatonergicN-acetyl-5-methoxytryptamine
The circadian pacemaker in the suprachiasmatic nucleus has a direct neural connection to the pineal gland, which releases the hormone melatonin at night.

Cortisol

stress hormonestress hormoneshydrocortisone
Cortisol levels typically rise throughout the night, peak in the awakening hours, and diminish during the day.

Phase response curve

delaying effectsdim-light melatonin onsetphase response (resetting) curves
Short pulses of light, at the right moment in the circadian cycle, can significantly 'reset' the internal clock.

Glycogen

glycogen depositsglycogen (n)glycogen deposits
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.

Frontal lobe

frontal cortexfrontalfrontal lobes
Sleep deprivation tends to cause slower brain waves in the frontal cortex, shortened attention span, higher anxiety, impaired memory, and a grouchy mood.

Medical imaging

imagingdiagnostic imagingdiagnostic radiology
Neurophysiological and functional imaging studies have demonstrated that frontal regions of the brain are particularly responsive to homeostatic sleep pressure.

Developed country

developed countriesdeveloped worlddeveloped
It is also unclear whether the prevalence of sleep debt among adults has changed appreciably in the industrialized world in recent decades.

Western world

WesternWestthe West
It is likely that in Western societies, children are sleeping less than they previously have.

Coffee

coffee beansblack coffeegourmet coffee
Coffee and caffeine temporarily block the effect of adenosine, prolong sleep latency, and reduce total sleep time and quality.

Time zone

Sri Lanka Standard Time Zonetime zoneslocal time
Humans are also influenced by aspects of social time, such as the hours when other people are awake, the hours when work is required, the time on the clock, etc. Time zones, standard times used to unify the timing for people in the same area, correspond only approximately to the natural rising and setting of the sun.

Time in China

China StandardChina Standard TimeCST
The approximate nature of the timezone can be shown with China, a country which used to span five time zones and now officially uses only one (UTC+8).

Industrial Revolution

industrialindustrialismindustrial era
Bimodal sleep in humans was more common before the industrial revolution.

Lark (person)

larkEarly birdday person
Different characteristic sleep patterns, such as the familiarly so-called "early bird" and "night owl", are called chronotypes.

BHLHE41

DEC2BHLHB3
Genes which may influence sleep include ABCC9, DEC2, and variants near PAX 8 and VRK2.

PAX8

paired box gene 8PAX 8
Genes which may influence sleep include ABCC9, DEC2, and variants near PAX 8 and VRK2.

VRK2

Genes which may influence sleep include ABCC9, DEC2, and variants near PAX 8 and VRK2.

Major depressive disorder

depressionclinical depressionmajor depression
Sleep difficulties are furthermore associated with psychiatric disorders such as depression, alcoholism, and bipolar disorder.

Alcoholism

alcoholicalcoholicsalcohol
Sleep difficulties are furthermore associated with psychiatric disorders such as depression, alcoholism, and bipolar disorder.

Bipolar disorder

bipolarmanic depressionmanic depressive
Sleep difficulties are furthermore associated with psychiatric disorders such as depression, alcoholism, and bipolar disorder.

Infant

neonatalinfancynewborn
Children need many hours of sleep per day in order to develop and function properly: up to 18 hours for newborn babies, with a declining rate as a child ages.

National Sleep Foundation

Early in 2015, after a two-year study, the National Sleep Foundation in the US announced newly revised recommendations as shown in the table below.

Reactive oxygen species

ROSreactive oxygenoxygen radicals
While awake, metabolism generates reactive oxygen species, which are damaging to cells.

Wound healing

wound repairscabvulnerary
Studies suggest that sleep deprivation may impair the body's ability to heal wounds.

Somatic (biology)

somaticsomasomatic cells
The effect of sleep duration on somatic growth is not completely known.