During a typical night’s sleep cycle, there are several stages of sleep: N1, N2, N3, and N4. If people are sleep deprived, they will experience negative impacts on their ability to learn and their health.
To began, the first stage of sleep, N1 (NREM Stage 1), is light sleep. As theta wave activity increases and alpha wave activity fades away, people are said to be entering N1 sleep, or light sleep. In this stage, there are several interesting things that can happen in this non-REM stage of sleep. First, if people are awakened at this point, they will probably not believe that they were actually asleep. Also, they may experience vivid visual events called hypnogogic images or hallucinations. However, a much more common occurrence is the hypnogogic jerk. A hypnogogic jerk occurs when a person is drifting off to sleep when his or her knees, legs, or sometimes the whole body gives a big jerk.
After going through the first stage
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Delta waves increase during this stage from about 20 percent to more than 50 percent of total brain activity. During this stage, growth hormones (GH) are released from the pituitary gland and reach their peak. The body is at the lowest level of functioning. Eventually, the delta waves become the dominant brain activity for this stage of sleep. In this stage, a person is in deep sleep, and this is the time when body growth occurs. After spending some time in N3, the sleeping person will go back up through N2 and then into a stage in which body temperature increases to near-waking levels, the eyes move rapidly under the eyelids, the heart beats much faster, and brain waves resemble beta waves-the kind of brain activity that usually signals wakefulness. The person is still asleep but in the stage known as rapid eye movement sleep (REM). REM sleep is associated with dreaming, and 90 percent of dreams actually take place in REM