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