Sleep Protects the Brain

Posted on by Jesse Santiano, M.D.

Four in 10 adults do not get enough sleep according to a 2014 Gallup poll. I suspect it is a lot more.

Sleep deprivation can occur in three different ways. First is sleep fragmentation, where a continuous sleep is broken up. The second is ‘selective sleep restriction’ that occurs in obstructive sleep apnea. This results in a lack of REM sleep. The third kind is sleep deprivation or ‘sleep debt’ where only a few hours or no sleep at all happens.

The Bad Effects of Poor Sleep

Lack of sleep produces memory problems, elevates stress levels, causes difficulty in focus and concentration, and affects behavior.

Higher-order executive function, attention, and many decision-making processes are also affected. The effects of poor sleep are very similar to drunk-driving.

What Happens to the Brain if Sleep Deprived?

During the waking hours, the brain is very good at multi-tasking. It detects and processes different stimuli, processes new information, solves problems while controlling movement, maintaining balance, and processing speech.

All of these functions are made possible by the neurons working together through multiple connections. Neurons are electrically excitable brain cells that are responsible for brain function. The electrical signals are converted to chemical signals that are carried out by  the neurotransmitters.

Some of the neurotransmitters are histamine, norepinephrine, and serotonin. To receive the message of the neurotransmitter, receptors on the receiving neurons have to be present and fully functional. The receptors are like a baseball mitt that catches a baseball.

After several hours of mental work, the receptors start to wear out and cannot process the signals from the neurotransmitters. That is why it is harder to focus and think after several hours or studying.  The solution is to rest the brain and if possible to take a nap.

SynapseSchematic_en.svg
The synapse is the connection between the neurons

Why Is Napping Good?

During a short nap, non-rapid eye movement sleep or NREM sleep occurs.  NREM sleep is the first stage of sleep in contrast to the deeper REM sleep that follows and takes much longer to occur.  NREM Sleep is when the neurotransmitter receptors are turned ‘off.’ This ‘rest’ by the receptors allows them to regain their sensitivity.

That is why a short nap may be enough to refresh a tired brain to continue a high mental performance.

Brain Activity Produces Waste Products

All of these brain and mental activities mentioned above require fuel to happen. Just like a car that requires gasoline and produces pollution, metabolic waste products are generated in the brain as it consumes fuel.

The examples of waste products are methylglyoxal that results in the production of advanced glycation end-products or AGEs. AGEs contribute to Alzheimer’s disease and other neurodegenerative diseases and Parkinson’s disease. AGEs also destroys the blood vessels and compromises blood supply. 

Glycation end-products also consume glutathione that is needed to neutralize free radicals. Lack of glutathione thus results in uncontrolled free radical formation and further cellular injury.

Other waste products are beta-amyloid, α-synuclein, and tau proteins. Like excess beta-amyloid associated with Alzheimer’s disease, the other waste products in excess has been implicated in the formation of other neurodegenerative diseases like the Lewy Body disease, and Fronto-Temporal Dementia.

1317_CFS_Circulation
Cerebrospinal fluid circulation

Sleep is When the Brain Gets Cleaned-Up

While asleep, the garbage collecting system of the brain is hard at work.

The Glymphatic system

Outside the brain, the circulating wastes are brought to the liver and kidneys by the lymphatic and circulatory system for detoxification.

In the brain, the glymphatic system is the one that clears the debris.  The word glymphatic is a combination of the words ‘gli’ from glial cells and lymphatic.

The glial cells, in contrast to neurons, are brain cells that do not have electrical impulses. The glial cells are for support, maintenance, and protection of the neurons.

While sleeping, the glial channels or glymphatic channels flowing between the brain cells increase in size. The larger size accommodates more cerebrospinal fluid to wash out more waste. These toxic metabolites are then transferred thru a one-way system outside of the brain to the systemic circulation to eventually be broken down by the liver.

Benefits of Sleep

The improved sensitivity of the neurotransmitter receptors during sleep and the removal of waste results in the regeneration of the different parts of the brain for the continuance of normal brain function.   

As a result, memory improves, and previous experiences blend with new knowledge to contribute to learning.

The benefits of sleep can be felt immediately and also have long-lasting effects on the prevention of dementia. 

Only One at a Time

Being awake and cleaning itself are two things that the brain cannot multi-task. The brain can only clean-up when it is asleep.

How Long Should You Sleep?

Studies have shown that 7 hours and others show 8 hours of sleep is needed.  My gauge is that if I wake up and I am not desperate for a stimulant like coffee, then I had enough sleep.

Like nature, the body runs in cycles. Day and night. Fasting and feasting. Eating and elimination. Work and rest.

Sleeping may look uneventful, but it is the best preparation for the mental challenges the next day.

Thank you for reading. Feel free to share.

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References:

  1. The Neuroprotective Aspects of Sleep. Andy R. Eugene, Jolanta Masiak. MEDtube Sci. 2015 Mar; 3(1): 35–40. PMCID: PMC4651462
  2. Sleep Drives Metabolite Clearance from the Adult Brain. Lulu Xie, Hongyi Kang, Qiwu Xu, Michael J. Chen, Yonghong Liao, Meenakshisundaram Thiyagarajan, John O’Donnell, Daniel J. Christensen, Charles Nicholson, Jeffrey J. Iliff, Takahiro Takano, Rashid Deane, Maiken Nedergaard. Science. Author manuscript; available in PMC 2014 Oct 18. Published in final edited form as Science. 2013 Oct 18; 342(6156): 10.1126/science.1241224. doi: 10.1126/science.1241224
  3. Don’t Lose Sleep Over Neurodegeneration-It Helps Clear Amyloid Beta. John McKinley, Allan McCarthy, Timothy Lynch. Front Neurol. 2013; 4: 206. Published online 2013 Dec 19. doi: 10.3389/fneur.2013.00206. PMCID: PMC3867735
  4. The Glymphatic System – A Beginner’s Guide. Nadia Aalling Jessen, Anne Sofie Finmann Munk, Iben Lundgaard, Maiken Nedergaard. Neurochem Res. Author manuscript; available in PMC 2016 Dec 1. Published in final edited form as Neurochem Res. 2015 Dec; 40(12): 2583–2599. Published online 2015 May 7. doi: 10.1007/s11064-015-1581-6 PMCID: PMC4636982
  5. A Cellular Perspective on Brain Energy Metabolism and Functional Imaging
    Pierre J.Magistretti, IgorAllama. Neuron. Volume 86, Issue 4, 20 May 2015, Pages 883-901

 Image Credits:

Synapse By Thomas Splettstoesser (www.scistyle.com) – Own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=41349083

The Cerebrospinal fluid By OpenStax – https://cnx.org/contents/FPtK1zmh@8.25:fEI3C8Ot@10/Preface, CC BY 4.0, https://commons.wikimedia.org/w/index.php?curid=30147960

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