Sleep Cycles: One rapid eye movement (REM) stage and three non-REM stages that altogether last about 90 to 120 minutes Benefits: Physical and mental recuperation and memory consolidation Disorders: ...

When a person is asleep, their core body temperature drops. Heart rate and breathing also slow down and overall metabolic activity decreases by about 10%. A sleeping body may seem inactive at first ...

Learn facts about sleep, during which the body rests, recuperates and performs essential repairs. When you purchase through links on our site, we may earn an affiliate commission. Here’s how it works.