Glymphatics - Literally Clearing Your Head

How the brain clears its waste as you sleep - Genius!

We always knew what an amazing organ the brain is. Humans don’t have the biggest brains in the world, but we do have the highest weight of brain tissue relative to our weight, and we cram a ton of neurons (brain cells) in there.

We didn’t (and still don’t) know exactly how it works.

I love that we’ve been studying brains for hundreds of years and that we’re still learning about them. Every day is a school day! We’re still constantly learning. I learned anatomy at Med School in Glasgow in a windowless basement in 1988. This Glymphatic System wasn’t even on the horizon then.

OK, what is it?

We have lymphatics throughout the body. They’re channels that clear waste products from tissues back to the bloodstream so that they can be eliminated. There’s a great wee video here that describes how they work. It’s for parents and is brief, informative and clear.

Essentially fluid and proteins constantly leak out of blood vessels. Lymphatic channels allow them to get back to the bloodstream so we don’t just keep swelling up more and more.

How awful would that be?

While they’re at it, they also have white blood cells which pick up and demolish germs or other harmful substances. Along these channels are filter stations (lymph nodes). These tend to clump in risky areas (bowel, underarms etc). Some are just under the skin where we can feel them, and some are buried deeper and we’d never feel them, like around the bowel or in the chest.

When your ‘glands are up’ this is the lymph nodes working super hard and getting bigger and harder to let us know that they are working hard!

BUT THERE ARE NO LYMPHATICS IN THE BRAIN

Ok, stuff still leaks out though. That’s just physics. Our heads don’t just keep swelling and swelling — the skull stops that.

It turns out that there are some lymphatics in the brain in specific areas. Not enough though.

So how do these bits get out?

There had to be an alternative (and there is, though it’s still controversial).

The brain is unique (in many ways). It is protected from rogue materials getting in in a number of ways. One of these is having its own system of fluid (separate from the body’s systems) for delivering essential fuel and other good stuff like glucose and oxygen.

The most effective way it does this is via the so-called Blood Brain Barrier (BBB). Anything above a certain size can’t pass itself. Anything bigger needs a friend (transporter) to get it in. So things like oxygen and water pass on their own. Glucose and amino acids need help. Even bigger things bypass this system but we know they still get there. It’s been suggested that they go around and alongside blood vessels. They even use the pulsing of the arteries to push them into the brain.

When waste products need to leave the brain, this same pulsing pushes them around the venous system in the brain and back into the circulation.

The really interesting bit?

In non-rapid eye movement (quiescent) sleep, the process is increased by around 60% so that it really does empty while we sleep. It’s slow and sluggish in the daytime.

How cool is that?

What a wonderful process to have evolved! Literally emptying the bins overnight. It also means that getting enough sleep is essential to function well in the day.

One of the proteins excreted is Amyloid B. Sounds benign but when this bad boy manages to form clumps or plaques in the brain, it can lead to Alzheimer’s amongst other issues.

I’ll write more on sleep too, but the quickest hack is to get out in genuine sunlight as early as possible in the day. The blue light in the early morning switches off our melatonin (the sleep hormone). This wakes us up and also rests our clock to make us feel sleepier that night.

Sleep (and quality sleep) is the cheapest and best quality medicine.

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