By Ergotherapist Pia Beck
The human body uses energy during every waking hour. When energy is burned, a neurotransmitter called Adenosine, which inhibits the brain's ability to send nerve signals, accumulates in the brain. The concentration of Adenosine increases with increasing brain activity during the day. The higher the level of Adenosine in the brain, the sleepier we become.
During the evening, the concentration of Adenosine becomes so high that the brain gradually slows down, and we start feeling tired.
Scientists have proven that a good night's sleep, and especially deep sleep, resets the level of Adenosine and other toxins, and makes us feel awake and ready for a new day. If we do not get enough sleep, there will be an increased amount of toxins in our brain, and we will, therefore, more quickly feel tired and unwell the next day. In addition, lack of sleep is also linked to the development of chronic diseases such as diabetes, cardiovascular disease, depression, and obesity. That is why we all need a good night’s sleep.
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The interesting question then is how the level of Adenosine is being “reset”. This is exactly what a research team, led by Maiken Nedergaard, investigated in 2012, making them the first to describe the brain's cleaning system.
The system functions in part as the lymphatic system in the rest of the body, and the team, therefore, named it the glymphatic system (‘g’ stands for glial cells). The glymphatic system consists of a macroscopic web of perivascular tunnels that eliminates waste in the brain.
Some aspects of the glymphatic system were described by previous research, but no one had previously explored how the brain disposes of waste products, and that it primarily happens while we sleep.
Although research into the glymphatic system remains new, it is supported by what we already know about the biological necessity of sleep. The results indicate that waste products will accumulate in the brain and break down brain cells if we do not get regular sleep.
In their experiments on sleeping mice, the researchers were able to see that the space (the interstitial space) that surrounds our nerve cells increases by 60% during sleep as the brain's support cells (also called glial cells) temporarily shrink. This increased space allows for a faster exchange of interstitial fluid with spinal fluid. This exchange is called the glymphatic clearance and it is through this system the waste products are eliminated through the kidneys or for degradation in the liver.
With knowledge of the glymphatic system or the human washing machine, it becomes clear that when we lack sleep or have slept poorly, our brains have not been washed sufficiently clean. But even though we have now gained more knowledge about how waste products from the brain are eliminated during sleep, some important details about what the glymphatic system actually looks like are still missing.
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Until recently, it has not been possible, with the available scanning techniques to see exactly how the brain's cleaning system worked. However, a new scanning technique was recently introduced making it possible to see the tunnels of the glymphatic system. The new scanning technology has been dubbed vDISCO and was developed by a Turkish neuroscientist named Ali Ertürk.
From mouse experiments, it can be seen that in a mammal’s brain there are lymphatic vessels that connect the brain directly to the skull. These vessels are so microscopic that they would never have been detected if the mouse brain had been removed from the skull.
This new technique is likely to give researchers the opportunity to answer a wide range of interesting questions such as; What does the glymphatic system look like in people with Alzheimer's compared to healthy peers? What happens to the system when you hit your head? And could it be that severe depression is affecting this perivascular system?
We do not yet have the answers to these questions. But there is no doubt that good, deep sleep is essential to our well-being and health.
Therefore, it is more important than ever to ensure that clients, residents, and patients have a good quality of sleep.