2019_FlipBook_Insel_Connect Core Concepts in Health_Brief_16e

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4 Sleep C H A P T E R O B J E C T I V E S ■ Identify the three stages of sleep ■ Understand how to apply good sleep habits ■ Explain the health-related benefits of sleep and the consequences of disrupted sleep ■ Understand changing sleep needs throughout the life span ■ List common sleep disorders, their symptoms, and their treatments ■ Understand the natural pattern of sleepiness and alertness throughout the day ■ Understand sleep disrupters and how to reduce their effects W e spend almost one-third of our lives asleep, but few of us understand what sleep is for and why it is necessary for our health. Since we are mostly unconscious during sleep, it is not uncommon to feel that we could be better off if we did not need sleep, and it can be tempting to cut back on sleep to make more time for entertainment or work. As we learn more about how sleep promotes all aspects of our health, how- ever, we see that we should make every effort to avoid missing it. SLEEP BIOLOGY Sleep affects almost all systems of the body, including the re- spiratory, cardiovascular, endocrine, gastrointestinal, urinary, and nervous systems. When we fall asleep, our heart rate and respiratory rates slow, our blood pressure drops, and our body temperature declines. Our consciousness is also pro- foundly changed during sleep. Sleep Stages Even though we are not conscious when we are sleeping, our brains are still active. Sleep is divided into distinct stages characterized by different patterns of electrical brain activity. The way these patterns come together is called sleep architecture, and it changes over the course of the life span. Brain activity during sleep is typically measured by a mon- itoring device called an electroencephalogram (EEG). During wakefulness, when a person is quietly resting with eyes closed, the EEG shows a pattern called the alpha rhythm. This pattern is characterized by regular brain waves that occur 8–10 times per second. These brain waves change, and different parts of the brain are activated or suppressed as a person progresses through the three stages of sleep. Stages I–III: NREM Sleep The first three stages of sleep are grouped together as non–rapid eye movement (NREM) sleep. The purpose of NREM sleep remains mysterious, but ©Image Source, all rights reserved. T E R M electroencephalogram (EEG) A monitoring device that records brain activity. non–rapid eye movement (NREM) sleep Of two main sleep phases, the one that constitutes three substages, including that with the deepest sleep and slow-wave brain activity. T E R M S C H A P T E R

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