Saturday, May 10, 2008

Sleep is very important for normal human functioning in their everyday lives. There is also number of causes of sleep, however it is not completely confirmed exactly how much is necessary or even why we sleep.
Researchers believe sleep is caused by chemical reactions in the brain. Eighteen chemical reactions were analyzed and one major catalyst called Factor S was found to be causing some animals to sleep. When this chemical was taken from a sleepy goat and inserted into awakened animals, the fell asleep instantly. Some humans however have stayed awake for several days indicating that Factor S does not have the same influence on people.
The reasons for sleeping at the moment are believed to be for regenerating our bodies and brain so that we can be more effective in our everyday tasks when we wake up. Earlier explanations claim it is for conservation of energy while they do not hunt for food at night and helps protection from predators.
Researchers have looked further at the reasons for sleep by examining brains. The reticular activating system (RAS) in cats is diminished while sleeping which in turn decreased arousal levels in the brain. Anything that spurs the RAS will wake up an animal. For humans, this functions the same way, so any warnings of sirens or loud noises will trigger attention to our brain, but since the RAS is actively diminished in our sleep, the siren or noises will be ignored and perhaps converted to dreams. Another area of study is the brain stem where a "sleep centre" is located. Here we will find two sections of distinct duties: REM (rapid eye movement) and NREM (non-rapid eye movement) states of sleep.
The daily, monthly and annual cycles are greatly determined by the environment, mainly sunlight. People's vision of the environment forms messages to the central nervous system and in turn affects their biological cycles. For example, an experiment in 1988, where a French woman spent 111 days in a cave, flowing with her natural instincts, with no medium to calculate time, slept for thirty one hours at one stage. Similarly, there have been recordings of people staying awake for up to fifty hours. Sunlight is also believed to affect people's emotions and reset their biological clocks. Research was also conducted in this area. Night-shift workers were exposed to bright light at night and kept in the dark during the day for a week; and consequently, they became more alert at midnight, and slept more comfortably during the day.
Scientists are still not exactly sure on how much sleep people need as it varies greatly for many people. On average people sleep for seven to eight hours but there are others who only need three hours sleep and some who need up to eleven hours sleep. Also, like the experiment with the French woman, some people have slept up to thirty-one hours. There have been other experiments conducted where volunteered people are kept awake for 200 hours. They showed signs of extreme irritably, lack of creativity and concentration, but as soon as they were placed back into their regular biological sleeping patterns, they were back to their normal selves, fully recovered and functioning. This just showed that there are no long lasting effects or health hazards on people if they were lacking sleep. Those who work long hours, study and have late night parties will effect others though, since their reactivity levels, concentration, or lowered academics can cause accidents such as drowsiness when driving.
The natural rhythm of human bodies are sometimes disrupted by measures of time such as clocks, watches, and time schedules. These factors influence many biological functions of humans daily such as metabolism, alertness, sleep and wake status, body temperature, blood pressure and level of hormones. For instance, people are more alert in the morning and early evening; and fairly drowsy mid day and towards late evening again.
Other influences on human function though may be monthly or yearly for example, T-cells are more common during winter to fight infections. These functions are adapted by humans, however, they will vary if the biological time or environment changes. A good example would be "jet lag" which occurs when people travel great distances on earth (or even out in space) between time zones. So someone in New York may leave at 9am and drive in London at 7pm but the biological clock would indicate the time as 4am. This is a dramatic change and it would take a few days to readjust sleeping patterns. A similar problem would occur if people change from day shifts at work to night shifts. Instead of being awake during the day, they now must be awake at night and sleep throughout the day. This variation in time can cause weight loss, irritability, health problems, insomnia, and extreme drowsiness. Research has found that the older people are, the lesser the need for sleep but that is also in proportion to reduced alertness.
Although sleeping just seems like a resting period for most people, a further analysis on this reveals certain activities and biological patterns occurring.
REM sleep, sometimes referred to as paradoxical sleep, occurs while people are at stage 1 sleep. At this point, brain activity, blood pressure, heart rate and other biological conditions, will increase to a level as though the person is conscience. The person's body will be paralyzed deep into his sleep and the eyes will continually moving, hence it is called rapid eye movement. Scientists found that during this period, people are dreaming, whether they remember the dream or not is another issue. The reasoning behind the movement of the eyes though are not confirmed as yet but it is possible that the sleeper is following the actions of his dream. One experiment showed a sleeper moving his eye from left to right constantly. He was waken up immediately and an explanation of watching a tennis match where the ball moved from side to side was revealed. This however is not sufficient proof. People who were disturbed during their REM time in some research experiments have demonstrated an increase in REM time when they fall back into their sleep. This gives the impression that REM time is necessary otherwise the body will not function properly.
Scientists investigate the sleeping patterns by measuring electrical activity inside the brain called ectroencephalogram (EED). Probes from an egg machine are attached to the sleepers head and electrical discharges are detected to be pulsing wave models of different amplitudes. Other instruments measuring body and eye movement show certain activities as well.
There are four significant stages of sleeping, all having their unique wave patterns to indicate the stage. This cycles throughout a persons sleep and it will last for approximately ninety minutes.
People will first progressively start from an awake state to hypnogogic state where they will be able to see still images but dreaming would not occur at this early stage. Then they proceed into the 4 stages of NREM.
Stage 1: Brain produces rapid low voltage waves here. Light sleep.
Stage 2: It will be more difficult to wake up someone at stage 2 who is falling deeper into his sleep. Slower wave amplitudes are found along with irregular sharp waves called "sleep spindles". This stage takes up half the cycle time.
Stage 3: Wave become much slower, higher, and lower at the peaks. Person is very deep into his sleep.
Stage 4:Wave pattern is even slower. By this stage, the person is least conscience of surroundings.
After stage 4, the sleep will go back to stage 3 and 2 but will not go to stage 1. Stage 1 is replaced by REM. Which is a state of dreaming. Eight to fifteen minutes will be spent here then it will cycle through again. Stage 4 is most likely to occur more dominant early part of the sleep. REM and stage 2 gradually take over until the person is awakening again. In one sleep, this will cycle about four to five times, so the less sleep, the less REM time a person will have.
For children, the ratio of REM time to NREM time is approximately 50:50 whereas young adults have a ratio of 25:75. Scientists believe this is the case due to infants learning a great deal more than adults as they exposed to newer environments. REM time will increase for people with more stress in life as well.
There are many biological needs for sleep that can lead to other influences of lifestyle as well as regular or irregular cycles occurring within our body systems. These in turn can effect peoples sleeping stages of REM and NREM. It is best to sleep as much as an individual needs to maintain a healthy body.

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