All About Sleep
Sleep is a condition of the body and mind when each night the nervous system is relatively inactive, the eyes are closed, muscles relaxed, and consciousness mostly suspended for several hours. There are 24 hours in one day, 168 hours in a week and 8,760 hours in a year. The average amount of sleep many people get each day should be about 8 hours, which is one-third of a day. If a person lives to be 90 years old, he or she will have slept for about 30 years of life. Every living thing needs sleep and rest.
During sleep, the brain maintains proper blood sugar levels, regulates hormones that control appetite and metabolism, and reduces high blood pressure. A good night's sleep leads to better physical, mental, and emotional health. A person may often feel cranky and tired, have a short temper, and are unable to think clearly without enough sleep. A person may struggle with following instructions, have an argument with a parent or friend, and have difficulty doing things that are usually easy to do. It becomes difficult to concentrate and to remember things.
In addition, the lack of sleep can affect growth and the immune system. A person could more easily become sick, and it takes longer to heal from a cold, flu, injuries, and other illnesses. Though scientists don't completely understand everything about sleep, they do know that most people have typical sleep patterns which include four stages or cycles of normal sleep.
Stage one is light sleep and the body begins to feel a little drowsy, and the stage only lasts about 1 to 10 minutes. If a person wakes during this stage, it will feel like they never slept at all. The breathing slows down, there is a regular heartbeat, but blood pressure and brain temperature decrease. During stage one a hypnic jerk like a twitch may occur causing a person to wake and may take place if a person dozes off during class at a desk and suddenly awakes, they may feel like their falling.
Stage two is a slightly deeper sleep as the brain sends signals to the muscles to relax, and the heart beats slower. The breathing slows down, and the body temperature drops as eye movement stops. The brain waves slow down with an occasional burst of rapid brain waves. This stage usually lasts about 20 minutes and it begins to become harder to awaken. About 45% of the night is stage two sleep.
Stage three lasts usually about 35 to 45 minutes after falling asleep and the brain waves further slow down and decrease. A person in this stage can easily sleep through many disturbances such as noises and movements and waking up will cause disorientation and confusion for a few moments. Other names for this stage include 'slow-wave sleep' and 'Delta sleep'. Sleepwalking, night terrors, and sleep talking may occur during this stage and the next stage.
Stage four is the very deepest sleep and it is very difficult to be awaken sometimes. REM or Rapid Eye Movement occurs during this stage, which lasts about 10 minutes as the eyes move rapidly in all directions. Powerful dreams take place, increase in heart and respiration rates, rhythms become irregular, lasts usually longer than other stages, up to an hour, and it occurs about 90 minutes after falling asleep.
The four stages are part of the typical sleep cycle, and a person goes through four to five cycles each night. The first cycle lasts about 90 minutes and subsequent cycles last between 100 to 120 minutes. After REM sleep, the person usually returns to Stage 1 and light sleep. As the night continues into the morning, REM sleep time increases and deep sleep time decreases. Deep sleep provides the most rest for a person and will not be affected by a short nap during the day. However, if a longer sleep reaches deep sleep, it becomes more difficult to get a good night's sleep because your need is reduced.
The amount of sleep a person needs usually depends on their age. Most kids between age 5 and 12 need from 9.5 to 11 hours of sleep each night, but as people age, 7 to 8 hours is usually effective.
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