Describe each of the five unique stages of the sleep cycle.

Answer:

Responses may vary but should include some or all of the following information: The sleep cycle has five stages: stages 1-4 and the REM (rapid eye motion) sleep stage. Stages 1-4 are also known as NREM or non-REM sleep. During stage 1 sleep, the brain is dominated by theta waves. The sleeper is in a very light sleep with closed eyes, but the sleep is very light and it is easy to be woken up. Indeed, sometimes a person wakes up with a start in a phenomenon called a hypnic jerk. During stage 2 sleep, the sleeper’s muscles begin to slowly contract and relax as the sleeper twitches. The body begins to slow: heart rate, breathing pattern, and body temperature all fall during this stage. The brain continues to be dominated by theta waves, but it will begin to contain deeper delta waves. Stages 3 and 4 sleep are very similar. Usually, scientists differentiate the two categories by stating that during stage 3, less than 50 percent of brain waves are delta waves, and during stage 4, more than 50 percent of brain waves are delta. Some scientists are even beginning to classify these groups together into one stage 3 category dominated by delta waves. It is during these stages of sleep that the sleeper is most deeply asleep and is receiving the most intense physical and psychological recovery. The last stage of sleep is known as REM sleep, so named because of the rapid eye movements that accompany its occurrence. During this stage of sleep, the sleeper’s brainwave pattern begins to show much more activity. In fact, the brain waves of this stage closely resemble the alpha or beta wave pattern of an awakened person. It is during this stage that a person will experience dreams.