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We know that our hair often looks like birds have been nesting in it overnight. There is no actual evidence to support this claim. However, there are some interesting and necessary changes taking place in your body while you sleep that can be backed scientifically.
For example, did you know that being both tired and hungry simultaneously can be explained scientifically? WebMD calls sleep "nutrition for the brain." The hormone ghrelin signals hunger, and the hormone leptin tells you when you're full. When you sleep, your leptin levels increase and your ghrelin levels decrease. It's like hitting a hunger reset button every night.
During rapid eye movement sleep, which accounts for about 25 percent of an adult's total sleeping time, the mind "combines certain associative elements into new combinations that are necessary or helpful for problem solving," according to an article in medicalnewstoday.com This contributes to those great ideas you have first thing in the morning or in that space between being fully asleep and fully awake. In this stage of sleep, the mind also processes information you might be worried about, hence the idea "sleep on it, you'll feel better in the morning."
During deep sleep, your body turns inward and concentrates on repairing itself. Brain waves become slow and steady, muscle and tissues are repaired, blood pressure drops while blood supply is redirected to the muscles and your body secretes hormones, such as leptin and ghrelin. Another hormone, cortisol, dips at bedtime and increases while you sleep which helps you feel alert in the morning.
When you sleep your mind, as well as your body, regenerates. As anyone who has been there knows, depression affects your sleep cycle. The opposite is also true. Sleep disruption accentuates mood disorders. The Anxiety and Depression Association of America says, "Research also shows that some form of sleep disruption is present in nearly all psychiatric disorders." It also gives some guidelines to improving the quality of sleep.
Stages of sleep
The Sleep Foundation explains the four stages of non-rapid eye movement sleep as: Stage 1 is light sleep; Stage 2 is the onset of sleep; and Stages 3 and 4 are deep sleep. These are followed by REM sleep. A person will cycle through these stages several times during the night. The sleep-wake cycle is regulated by two separate but interacting processes called the circadian process, triggered by light and temperature, and the homeostatic, triggered by how long it has been since you last slept. Each stage of sleep is important to your mental, physical and emotional health.