Sleep is an altered state where people become relatively unaware of external stimulation. There are two main theories for why we sleep - the evolutionary theory which suggests it protects animals by keeping them safe at night, and the recuperative theory which says it conserves energy and allows the body to restore tissues depleted during waking hours. The circadian rhythm, an internally generated sleep-wake cycle connected to the 24-hour period of the earth's rotation, influences when we sleep at night. The amount of sleep needed decreases with age, from 20 hours for infants to 6 hours for elderly adults. Missing sleep can negatively impact both the body and brain by weakening the immune system, causing mood issues and decreased cognitive performance.

1. Doing by: Dr. Mohammed H. Al-nakhli
What Is Sleep?
• An alteredstate inwhichpeoplebecome relativelyunaware of external stimulation
Why Do We Sleep?
• EvolutionaryTheory:Protective function,keepspeople tuckingawayatnight,safe from
predators.
• Recuperative Theory:Conservesenergy,restoresbodytissuesdepletedduringdailyactivity
– REM: hormonesreleasedthatinfluence thinking&memoryformation,mental
organization;counteractfatigue,irritability,inattention
– NREM: body replenishesitself (tissue restorationandrelease of growthhormone)
Why Do We Sleep At Night?
• CircadianRhythm
– Internallygeneratedsleep/wake cycle connectedto24-hourpdof earth’srotation
How Much Sleep Do I Need?
• Infants
– 20 hours
• 50% REM
• Children/Adolescents
– 10 hours
• 25-30% REM
– BedLater, Up Later
• Adults
– 8 hours
• 20% or lessREM
• Elderly
– 6 hours
– BedLater, Up Earlier
What If I Miss Sleep?
• EffectsOnBody
– Immune systemweakens
– Metabolicmalfunction
– Variedbodytemp
• EffectsOnBrain
– Moodiness
– Decreasedcognitive performance
• Learn slower,rememberless,lossconcentration&creativity
– Blurredvision
– Disorganizedspeech
– Hallucinations