Part 3 of a 6-Part Series
Click here to read part one of this series.
“To sleep, perchance to dream.”
Ah Shakespeare. Sweet dreams, the ultimate good night’s sleep, something we all treasure. Dreams are just one part of our nighttime journey. Besides dreams, what else goes on while we sleep?
There is a kind of circadian rhythm dance of light and darkness that goes on within neuron centers inthe hypothalamus, thalamus, the brain stem, and the forebrain which produce both wakefulness and the need for sleep.
We have light sensitive neurons in the hypothalamus which produce neuro-chemicals that promote wakefulness. The longer we are awake, and as the day goes on, different neurons within the hypothalamus produce neuroactive chemicals, known as somnogens, that promote sleep. Somnogens accumulate during the day, promote drowsiness, and prepare the brain to sleep.
Eventually somnogens take over and we sleep. There are many different somnogens involved in sleep. The most studied somnogen is adenosine. It is interesting to note that caffeine (not just from coffee) blocks adenosine receptors, which is why caffeine helps to keep us awake.
Many people have heard of the somnogen Melatonin. It is often used as a helpful, natural aid to falling asleep. Two other very important neurochemicals are GABA and galanin. Both GABA and galanin are produced by neurons in the hypothalamus and are distributed throughout the brain. They inhibit all wake-promoting areas of the brain.
Stages of Our Sleep
Galanin is very important in learning and memory. It is during sleep that memories are laid down, another reason sleep is so important to learning.
So our neurochemicals have done their job and now we are asleep. Actually, sleeping is not just one simple activity. Sleep happens in cycles of about 90 minutes each. During these cycles, brain wave activity changes and activity in both brain and body also changes.
When we think about getting enough sleep, we also need to realize it is important to have enough complete sleep cycles. The quality of our sleep is just as important as how long we are sleeping and whether we constantly awaken or enjoy several uninterrupted sleep cycles.
Sleep Scientists Divide Sleep Cycles in Two Major Groups
- Rapid Eye Movement (REM)
- Non- Rapid Eye Movement (NREM).
NREM has three stages: N1, N2 and N3
N1 is our time of drowsiness and transition from being awake to falling asleep. This is that phase when we sometimes have sensations of falling or our limbs might jerk or we experience restless legs. Our brain wave activity is moving from Beta waves of 12 to 38 HZ, our waking active brain activity, to Alpha waves of 8 to 12 HZ, our calming, relaxing brain wave activity, on to Theta waves of 3 to 8 HZ. In this stage, we are not fully asleep, yet not fully awake. Our attention to outside stimuli diminishes. Our brains create a mixture of both Theta and Alpha as we drift from drowsiness of N1 into the next stage, N2.
In N2 we are in the most prominent sleep stage. We are deeply asleep and our brain waves consist of varying levels of the Theta wave frequency. We are not dreaming and we are not yet into our deepest sleep. Our brain activity becomes limited as we move into deep sleep.
It is during this phase of sleep, and the deeper stages of N2, that our body detoxifies, cells repair, divide, grow and develop, cell waste products are removed, and children actually grow. Our bodies are relaxed and waste products are sent to the kidneys and on to the bladder. That’s why we need to go to the bathroom as soon as we awaken, or sometimes during the night.
N3 is our Delta wave sleep of .5 to 3 HZ. We are now deeply asleep. All systems of the brain involved with wakefulness have been inhibited. Most neurons are quiet, except for specific neurons designed to inhibit wakefulness. This stage usually occurs within 15 to 45 minutes after the onset of sleep. The duration of deep slow wave sleep depends upon age. The older we are, the less time spent in this stage. Babies and young children spend the most time in Delta wave sleep.
Finally, we have REM sleep. This is a unique brain wave pattern all it’s own. This is the stage where we experience dreams. During REM sleep, our thalamus and cortical areas become active and our eyes move rapidly. Heart rate and breathing increase. Neurons are triggered in the brainstem and down the spinal cord, which produce paralysis of our muscles and limbs to prevent us from acting out our dreams.
REM sleep occurs about 80 to 85 minutes into the sleep cycle. REM sleep plays an important role in memory consolidation, the synthesis and organization of cognition, and mood regulation. Everyone dreams, we usually don’t remember them unless they wake us.
More About Sleep Yet to Come
Sleep and dreaming are essential to good health and clarity of thought. In the final segment of this series, I’ll discuss insomnia and tips for getting a restful, restorative night’s sleep.