The three stages of quiet sleep (non-REM sleep) Stage N1 Unless something disturbs the process, you will proceed smoothly through the three stages of quiet sleep. The transition to quiet sleep is a quick one that might be likened to flipping a switch-that is, you are either awake (switch on) or asleep (switch off), according to research. This is the alpha-wave pattern, characteristic of calm, relaxed wakefulness (see Figure 1). Once your eyes are closed and your brain no longer receives visual input, brain waves settle into a steady and rhythmic pattern of about 10 cycles per second. If you’re fully awake, an EEG records a messy, irregular scribble of activity. When you are awake, billions of brain cells receive and analyze sensory information and coordinate behavior by sending electrical impulses to one another. To an extent, the idea of “dropping” into sleep parallels changes in brain-wave patterns at the onset of non-REM sleep. Sleep specialists have called quiet or non-REM sleep “an idling brain in a movable body.” During this phase, thinking and most bodily functions slow down, but movement can still occur, and a person often shifts position while sinking into deeper stages of sleep. Surprisingly, they are as different from each other as either is from waking. Scientists divide sleep into two major types: The hormone induces drowsiness, and scientists believe its daily light-sensitive cycles help keep the sleep/wake cycle on track. Levels of melatonin begin climbing after dark and ebb after dawn. As a person reads clocks, follows work and train schedules, and demands that the body remain alert for certain tasks and social events, there is cognitive pressure to stay on schedule. The circadian rhythm disturbances and sleep problems that affect up to 90% of blind people demonstrate the importance of light to sleep/wake patterns. However, exposure at the wrong time can shift sleep and wakefulness to undesired times. Exposure to light at the right time helps keep the circadian clock on the correct time schedule. In societies where taking a siesta is the norm, people can respond to their bodies’ daily dips in alertness with a one- to two-hour afternoon nap during the workday and a correspondingly shorter sleep at night. Most Americans sleep during the night as dictated by their circadian rhythms, although many who work on weekdays nap in the afternoon on the weekends. When the investigators plotted the times when unplanned naps occurred, they found peaks between 2 a.m. Not surprisingly, many slipped into naps despite their best efforts not to. In one study, researchers instructed a group of people to try to stay awake for 24 hours. (“Circadian” means “about a day.”) This internal clock, which gradually becomes established during the first months of life, controls the daily ups and downs of biological patterns, including body temperature, blood pressure, and the release of hormones.Ĭircadian rhythms make people’s desire for sleep strongest between midnight and dawn, and to a lesser extent in mid-afternoon. For instance, a pacemaker-like mechanism in the brain regulates circadian rhythms. Affiliate Disclosure Your internal clock (circadian rhythms)Ĭertain brain structures and chemicals produce the states of sleeping and waking.
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