Sleep is a natural, recurring condition of the body and brain, characterized by decreased awareness, a suppressed sensory function, decreased motor activity, decreased concentration and disinterest, decreased emotional response, and decreased interactions with surrounding stimuli during rapid eye movement sleep (REMS). Sleep occurs during the period when the body is in a sleep phase between being awake and being asleep. During this sleep phase, the brain is in the most inactive state. Some research has found that the ability to learn decreases during sleep and some researchers believe that the human mind actually releases two chemicals during sleep: cortisol, which decreases as we sleep and human growth hormone (HGH), which increases as we sleep. Sleep also appears to relieve stress and anxiety. In the absence of proper sleep, the levels of cortisol and growth hormone remain high.
We have different sleep cycles depending on our stages of life. In babies, sleep cycles are much shorter than those in adults. Adults typically sleep for eight hours or longer and their sleep cycles are longer. Babies spend about ninety percent of their time asleep and reach their fourth stage of sleep only once per day. Adults sleep from seven to nine hours and awaken four to six times per night.
In the four stages of sleep described above, the baby spends about ninety percent of his time in deep sleep. During this time he is inactive and does not move, so his eyes move slowly and are dilated. As he reaches four days of age, he can begin to hear the sound and move his limbs, but he cannot talk and cannot open his eyes. At this time, he is ready to be lifted out of deep sleep and brought into the lighter stages of sleep.
When children reach their eight-week of age, they are starting to become more active. At this time, they are beginning to move their arms and legs, and they start to develop a sleep-wake cycle. At this time, their brains have enough energy to start learning what they need to do when they get home from school, but they do not yet have a sleep-wake cycle established. At this point, children are more tired than when they came home from school. Their brains are still active, but they are tired.
Children go through four different sleep stages during the course of a night. Each stage is designed to help them develop and mature emotionally and physically. They are: Stage I – little sleep, very sleepy; Stage II – light sleep, stage for learning; Stage III – moderate sleep, stage for thinking; Stage IV – deep sleep, stage for memory. Children generally enter Stage I when they enter the third trimester and remain in Stage I for the entire nine months of pregnancy.
Babies in Stage II experience four major changes in pattern. They experience much more sleep than they did in their Stage I sleep cycle. They may feel sleepy for longer periods, including all the time during sleep. They may seem inactive, or they may feel sluggish. They may even find themselves waking up suddenly, sometimes without being aware that they have done so.