The lymphatic system runs throughout our body, connecting our lymph glands. It was discovered in the sixteenth century. Most of the body’s organs remove dead cells and metabolic waste products using the lymphatic system. When a physician is palpating your lymph nodes, he or she is checking part of your lymph system. This is the easy part of the article. Stick with me for the rest to understand what this all has to do with sleep.
Glial cells are non-neuronal cells, that is, cells other than the nerve cells that conduct the messages throughout the brain and body. The glial cells were discovered in the nineteenth century. We’ve known throughout the twentieth century that certain glial cells search for and destroy pathogens and dead neurons. But until just nine years ago, it wasn’t clear to scientists how the brain got rid of its metabolic waste. A new “drainage” system in the body, in the brain specifically, was discovered by Dr. Maiken Nedergaard in 2012. Since it involves glial cells and acts like the lymphatic system, it was called the glymphatic system. Makes sense, right?
The glymphatic system consists of a tunnel around a tunnel. The inside tunnel consists of the arteries and arterioles in the pia. The pia is a membrane around the brain inside of the skull. Inside of this inner tunnel is where the blood is flowing. Astrocytes are a type of glial cell that looks somewhat like a star. They have feet that loosely wrap around all the small blood vessels in the brain to create the outer tunnel. Inside that outer tunnel flows cerebrospinal fluid (CSF).
The CSF flows out of the outer tunnel, flows past the neurons in the brain and flows into the local venues, and eventually out of the brain. Of course, it’s a bit more complicated than that. You can check out online the article The Glymphatic System: A Beginner’s Guide if you want the details. The flow of this fluid takes the metabolic wastes from the neurons out of the brain. The flow gets rid of pieces of beta-amyloid. These are broken pieces of protein that can build up over time and play a role in Alzheimer’s disease.
OK, here is the part I’ve been building up to. I hope you’re still with me. Norepinephrine is one of the neurotransmitters produced in the brain. When it’s produced, it wakes us up. It also inhibits the production of the CSF and causes swelling in cells of the glymphatic system. This swelling blocks the flow of the CSF through the brain when we are awake.
However, when we sleep, our brain cells don’t produce norepinephrine. More CSF is produced and the swelling in the cells of the glymphatic system goes down. The flow of the CSF through the brain is much more effective. This flow takes the neurotoxic waste products from the day out of the brain. So, when we’re asleep, the whole system is working to detoxify our brain.
So, how much sleep should we be getting so that our brain can clean itself? The World Health Organization and the National Sleep Foundation both recommend an average of seven to eight hours of sleep per night for adults. Too much sleep (like more than ten hours per day) isn’t good for us either, for reasons not relevant to this article.
I hope the take-home message for you from this blog is a greater understanding of how important getting a good night’s sleep is. For practical suggestions about getting a good night’s sleep, consult the book Why We Sleep by Matthew Walker, Ph.D. If you’re having problems sleeping, you might consider speaking to a therapist here at STA (call 201-488-6678) who can help you identify and remediate emotional issues that may be interfering with your sleep.