Numerous factors determine when and why you feel tired, full of energy, and hungry. A person’s state of consciousness and awareness varies throughout the day and depends on a person’s activity, environment, and time clock. As a human we have what is called circadian rhythms, which simply explains our daily highs and lows. An example of your basic up and down rhythm would be the sleep/wake cycle. Sunlight regulates the sleep/wake cycle by causing the suprachiasmatic nucleus to decrease its production of melatonin in the early morning and increase it in the evening. Melatonin is a hormone that if increased in blood levels makes an individual drowsy or tired and if decreased will make them more alert. Certain individuals will experience that their biological clock is often out of sync. This can be explained sometimes from either jet lag, working the night shifts or graveyards, and Monday-morning fog. Sleep in itself has its own biological patterns and rhythms. Hans Berger introduced the electroencephalograph to us so that we would be able to measure the patterns and rhythms of sleep through a record called an EEG. Two different patterns of sleep are REM sleep and NREM sleep. The NREM sleep actually has four stages involved in it. During the first stage a person becomes slightly drowsy because of the mixture of alpha and theta brain waves. At the second stage, an individual tends to have bursts of brain activity for a short time, which in terms are called sleep spindles. The second stage also involves theta brain waves and the beginning of delta waves. The third and fourth stages of NREM sleep are often referred to as “slow-wave sleep”. Both of these stages are measured by the amount of delta brain wave activity. During REM sleep, the sleeper is unconsciously active. His eyelids may flutter, he may have increased heart rate, and occasional muscle spasms. The two basic sleep theories are the evolutionary and restora...
