We spend an important part of our lives sleeping, yet many of us know so little about what happens to our brain and body when we sleep. This information is not necessary to know if we well or we have sleep difficulties, but knowing about it can make us understand, prevent and solve many sleep issues we might encounter.
What happens in our brain?
Since the 1930’s it is known that chemical reactions in our brains produce waves of electricity that can be monitored from our scalp. This can be done and recorded with an EEG (electroencephalogram) that measures cycles per second of the brain waves.
How frequent (fast or slow) and how big or small our brainwaves are depends of where in our brains they are produced, in how alert we are, and how urgent the message being transmitted is.
Now we know that sleep is an active and complex activity, not a time in which we shut down and be completely passive. Out of many studies, scientists converge in describing different stages of sleep which are determined by brainwave patterns, eye movement and muscle tone. There are two major, and very different, types of sleep:
Non-REM sleep – quiet sleep
REM (Rapid Eye Movement) sleep – dreaming sleep
This time we will focus in Non-REM Sleep:
The Non-REM sleep is a phase in which most physiological activities slow down, as well as our thinking.
When we are awake our brainwaves are fast since our neurons are receiving and processing information that comes from our senses, what we see, hear, touch, smell and taste. They are also coordinating our behavior, what we do and how we act and react. In addition to all that, our braincells maintain our physiological functions going. All this work done by our brain cells can be recorded as brainwaves.
When we want to go to sleep and close our eyes, our brain cells stop receiving input from what we see, progressively our body slows down and our brainwaves settle into a rhythmic and steady pattern, known as an alpha-state, in which we are in a calm and relaxed wakefulness. If nothing wakes us up, we smoothly go through the stages of non-REM sleep.
First Stage: we spend about 5 minutes in it, and it is the transition to light sleep. In this transition our body temperature decreases, our muscles relax, our eyes usually move from one side to the other, we become unaware of our surroundings but we can easily wake up.
Second Stage: We spend about half of our night’s sleep in this stage. At this point we have a sound sleep, our eyes are still in most cases, our breathing and heart rate are slower than when we are awake. Our brainwaves are irregular and we have brief moments of high activity in a low activity irregular brainwave pattern. Scientists believe this is what keeps us vigilant to wake up if we need to.
Deep Sleep Stages: This phases of deep sleep is believed to be the time that our body actually renews and repairs itself, it is the portion of sleep that we need to feel refreshed. In these stages our brainwaves become bigger and slower – delta waves. These slow, big and coordinated brainwaves result from the decreasing activity of our processing centers in our brains. At this point in sleep, it is difficult for us to wake up.