Do you sleep everyday? This question may look rubbish to almost all the people, because everyone will sleep atleast a minimum of 20% of a day. But how many of you know what happens every time we get a bit of shut eye? Sleep occurs in a recurring cycle of 90 to 110 minutes and is divided into two categories: 4 stages of non-REM and REM sleep.
Stage 1 - Light Sleep: In this stage of sleep, we're half awake and half asleep. Our muscle activity slows down and slight twitching may occur. This is a period of light sleep, meaning we can be awakened easily at this stage.
Stage 2 - True Sleep: Within ten minutes of light sleep, we enter this stage, which lasts around 20 minutes. The breathing pattern and heart rate start to slow down which accounts for the largest part of human sleep.
Stages 3 - Deep Sleep: Here, the brain begins to produce delta waves, a type of wave that is large (high amplitude) and slow (low frequency). Breathing and heart rate are at their lowest levels.
Stage 4 - Deep Sleep: It is characterized by rhythmic breathing and limited muscle activity. If we are awakened during deep sleep we do not adjust immediately and often feel groggy and disoriented for several minutes after waking up. Some children experience bed wetting, night terrors or sleepwalking during this stage.
The first rapid eye movement (REM) period usually begins about 70 to 90 minutes after we fall asleep. We have around three to five REM episodes a night. Although we are not conscious, the brain is very active - often more so than when we are awake. This is the period when most dreams occur. Our eyes dart around, our breathing rate and blood pressure rise. However, our bodies are effectively paralyzed, said to be nature's way of preventing us from acting out our dreams. After REM sleep, the whole cycle begins again.