3-1 Understanding Sleep

REM sleep

active stage of sleep during which your breathing changes, your heart rate and blood pressure rise, and your eyes dart around rapidly

sleep deficit

condition that occurs when people frequently get less sleep than they should

jet lag

fatigue that people feel after changing time zones when they travel

melatonin

hormone that increases feelings of relaxation and sleepiness and signals that it is time to go to sleep

circadian rhythms

naturally occurring physical, behavioral, and mental changes in the body that typically follow the 24-hour cycle of the sun

sleep-wake cycle

pattern of sleeping in a 24-hour period

short sleepers

people who can function well on less sleep than other people

sleep deprived

term used to describe a person who gets inadequate amounts of sleep