66 Lesson 3.1 Key Terms Key Terms sleep deprived term used to describe a person who gets inadequate amounts of sleep short sleepers people who can function well on less sleep than other people sleep deficit condition that occurs when people frequently get less sleep than they should 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 melatonin hormone that increases feelings of relaxation and sleepiness and signals that it is time to go to sleep jet lag fatigue that people feel after changing time zones when they travel REM sleep active stage of sleep during which your breathing changes, your heart rate and blood pressure rise, and your eyes dart around rapidly Learning Outcomes After studying this lesson, you will be able to • understand why sleep is important. • describe the sleep needs of each age group. • explain the science of sleep, the stages of sleep, and dreams. • determine the consequences of not getting enough sleep. Understanding Sleep Graphic Organizer Graphic Organizer The Importance of Sleep In a graphic organizer like the one shown below, write five to six statements about the importance of sleep to your health. As you read the lesson, add any health benefits of sleep that you did not previously know. iQoncept/Shutterstock.comco I need to sleep because... it enhances productivity iQoncept/Shutterstock