Copyright Goodheart-Willcox Co., Inc. Chapter 3 Getting the Sleep You Need 71 The first period of REM sleep usually occurs about 70 to 90 minutes after you fall asleep. REM sleep is an active stage of sleep during which a person’s breathing changes and becomes irregular, shallow, and more rapid. Heart rate and blood pressure also rise. A person’s eyes dart about rapidly under the eyelids (REM stands for rapid eye movement), and muscles are temporarily paralyzed. The first sleep cycles of the night contain relatively short REM periods and long periods of deep sleep (Stage 4). The periods of REM sleep get longer with each sleep cycle, while the deep sleep periods get shorter. There are smartphone apps available which track users' sleep cycle patterns (Figure 3.7). These apps can identify if the user is getting enough good quality sleep, and offer techniques and tools for falling and staying asleep. They can also wake the user at the ideal time, while entering the first stage of sleep. It is important to note, however, that many sleep experts do not believe that a sleep app can provide reliable, accurate data regarding a person’s quality of sleep. Dreaming Even though you may not remember your dreams, you do dream every night. On most nights, people spend more than two hours dreaming. Many of these dreams will last between 5 and 20 minutes. What a person dreams about, however, may change a lot from night to night. Sometimes dreams may closely relate to what is going on in someone’s daily life. At other times, dreams may appear bizarre and unreal. Sleep Stages Your body temperature starts to drop, your heart rate slows down, and your muscles relax. Stage 2 Your blood pressure lowers and your body is not sensitive to temperature. Stage 3 Your eyes and muscles stop activity completely. You are in a deep sleep and are very difficult to awaken. Stage 4 You enter REM sleep. Your breathing, heart rate, and blood pressure increase. Stage 5 You drift in and out of sleep and are easy to awaken. Y e Stage 1 One cycle: 90–110 minutes Figure 3.6 You should cycle through all five stages of sleep multiple times each night, experiencing noticeable changes in the body’s temperature, movement, and systems. During which stage of sleep does your blood pressure lower? Andrey_Popov/Shutterstock.com Figure 3.7 Smartphone apps can connect to devices, such as smart watches, which will record heart rate, blood pressure, and more to track the sleep patterns of the user.