Every human being requires sleep just like all other animals. It is important for all normal human beings to understand that sleep is usually part of the normal daily cycle. Having too much sleep or too little of it is always a problem for physical and psychological being. The natural human sleep is usually divided into rapid eye movement (REM) and the non-rapid eye movement (nREM). The two types of sleep are also grouped into sub-stages. During these stages, both the mind and the body usually react differently.
Each of the four sub-stages of the nonrapid eye movement usually lasts between five to fifteen minutes. When the person has gone through all the four stages of non-rapid eye movement, what follows is the rapid eye movement stage. The cycle goes on and on during the entire night sleeps. The first stage of the non-rapid eye movement is the time between being awake and when one falls asleep. In the second stage of non-rapid eye movement, the body goes under light sleep. The heart slows down and the body temperatures are reduced. In the third and fourth stages of non-rapid eye movement, the body is usually in deep sleep and the body is involved in the building of muscles and bones as well as generating new tissues.
After the end of the non-rapid eye movement cycle, the rapid eye movement eye cycle immediately begins. This is mostly after about one hour after falling asleep. During this stage, one may start dreaming and the eye can be seen moving rapidly under the eyelid. The breathing and the heartbeat are always increased during the rapid eye movement sleep. All the voluntary muscles of the body are usually paralyzed at the rapid eye movement stage.
Currently, there are no proven reasons to explain why we need rapid eye movement sleep. There are some theories that have been propounded to explain what exactly happens during this sleep. One theory states that the body needs rapid eye movement sleep to enable it to file all the activities of the day. There is also a theory that the state that during this sleep, the memory is at its creative process. This explains why some of the problems that seem to be difficult to understand become simpler after having enough sleep.
The number of hours that one requires to sleep usually varies from one person to the other. A newborn baby requires sleeping between sixteen and eighteen hours each day. A normal adult should get sleep of between six to eight hours each day. Sleep usually decreases with age and as one gets old they tend to sleep for fewer hours. Sleep is usually necessary for everyone. Insomnia can result in decreasing the immune system, sluggishness, slow memory functioning, and depression. Too much sleep is also a problem as one can become overweight and lead to major health problems. In case one has a sleeping problem, they should seek professional help to restore sleep to normal.