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Many of us choose to enjoy the effects of alcohol, and we know that drinking too much is a bad thing, but what kinds of things can actually happen when you drink too much for too long?

Annotations:
The Science of Hangovers https://youtu.be/v4IIFfguf1U
Does Alcohol Kill Brain Cells? https://youtu.be/TpgpSIGIczc

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Sources:
http://www.scientificamerican.com/magazine/sa-classics/intoxicating-the-science-of-alcohol/
http://www.bbc.co.uk/newsbeat/article/30350860/the-science-of-alcohol-how-booze-affects-your-body
http://www.nhs.uk/news/2011/10October/Documents/whats_your_poison_1.0.pdf
https://sites.duke.edu/apep/module-2-the-abcs-of-intoxication/content-getting-alcohol-to-the-brain-crossing-the-blood-brain-barrier/
http://www.ncbi.nlm.nih.gov/pubmed/15704345
http://pubs.niaaa.nih.gov/publications/AlcoholOverdoseFactsheet/Overdosefact.htm
http://science.howstuffworks.com/life/inside-the-mind/human-brain/alcoholism4.htm
https://www.nlm.nih.gov/medlineplus/alcoholismandalcoholabuse.html
http://www.mayoclinic.org/diseases-conditions/cirrhosis/home/ovc-20187218
https://www.nlm.nih.gov/medlineplus/ency/article/000771.htm
http://www.cancer.org/cancer/cancercauses/dietandphysicalactivity/alcohol-use-and-cancer
http://www.niaaa.nih.gov/alcohol-health/overview-alcohol-consumption/alcohol-facts-and-statistics
https://www.nlm.nih.gov/medlineplus/ency/article/000771.htm
https://www.ncbi.nlm.nih.gov/pubmed/20575793
https://www.ncbi.nlm.nih.gov/pubmed/20113871

Images:
https://commons.wikimedia.org/wiki/File:Ethanol-3D-balls.png
https://commons.wikimedia.org/wiki/File:Acetaldehyde-3D-balls.png
https://commons.wikimedia.org/wiki/File:Acetate-anion-3D-balls.png
https://commons.wikimedia.org/wiki/File:Blood_Brain_Barriere.jpg
https://commons.wikimedia.org/wiki/File:Chemical_synapse_schema_cropped.jpg
https://commons.wikimedia.org/wiki/File:GABA_3D_ball.png
https://commons.wikimedia.org/wiki/File:L-Glutamic-acid-3D-balls.png
https://commons.wikimedia.org/wiki/File:Gray677.png
https://commons.wikimedia.org/wiki/File:Prefrontal_cortex_(left)_-_lateral_view.png
https://commons.wikimedia.org/wiki/File:Limbic_lobe_animation.gif
https://commons.wikimedia.org/wiki/File:Blausen_0114_BrainstemAnatomy.png
https://commons.wikimedia.org/wiki/File:Liver_Cirrhosis.png
https://commons.wikimedia.org/wiki/File:Circulatory_System_en.svg
https://commons.wikimedia.org/wiki/File:Thiamine_cation_3D_ball.png
(Intro)

Ah, alcohol. It's known to make people all around the world feel a little more outgoing at dinners and dance parties. But the inside of your body sees alcohol as a poison, and it tries to get rid of it ASAP. Whatever your body can't process right away can end up in your brain, which affects how your cells interact with each other and causes all those things that we associate with drunkenness. So it's totally fine to have a beer or two with your drinking-aged friends. But consistently drinking way too much alcohol can get dangerous in the long run.

When you take a sip of an alcoholic beverage, the toxic stuff it contains, ethanol, also known as ethyl alcohol, is absorbed into your bloodstream through your stomach lining or small intestine. Your liver is responsible for filtering out this ethanol and breaking it down, using enzymes and other peptides, so your body can safely get rid of it.

First it's converted into acetaldehyde, which is toxic too and probably a big reason for those nasty hangovers. Then, another enzyme turns acetaldehyde into acetate, which is harmless and eventually excreted in urine. And your liver does its best to get rid of all the ethanol you're putting in your body. But if you keep refilling that wine glass, it has trouble keeping up. So any excess ethanol circulates in your bloodstream and eventually reaches your brain.

Now, usually, foreign substances like bacteria and toxins are kept out of your brain thanks to the blood-brain barrier, basically a filter made of specialized cells and proteins. But it's actually pretty easy for ethanol to get in, because it's attracted to fats, so it can pass through those fatty cell membranes. And once alcohol reaches the brain, it starts to mess with the signaling between neurons – aka brain cells.

The brain uses these chemicals called neurotransmitters to send messages between cells. The two most important ones are γ-aminobutyric acid, or GABA, and glutamate. GABA binds to specialized receptor proteins and causes neurons to send fewer signals so scientists say it's an inhibitory neurotransmitter. Glutamate, on the other hand, binds to receptors and causes neurons to send more signals so it's an excitatory neurotransmitter.

Ethanol interferes with this signaling by binding to both of these receptors, and changing the messages the neurons receive. Specifically, ethanol enhances GABA signaling and reduces glutamate signaling, which means there's more inhibitory signaling and slower brain activity overall. That's why alcohol is considered a depressant.

And its effects on different brain regions can cause different symptoms of drunkenness. For example, alcohol reduces activity in the cerebellum, which is responsible for motor coordination – causing all of that stumbling. It also suppresses the areas of the brain responsible for self-control and social inhibition, which makes us more outgoing, emotional, and prone to risky decisions. These effects go away as your body continues to process the ethanol.

And as far as we know, there aren't serious risks to moderate alcohol consumption. But ethanol is a toxin. So if you keep downing drink after drink in a short period of time, you can get alcohol poisoning – basically, a shutdown of the medulla, which is the brain region that manages vital life support functions, like breathing and heart rate. And there are long-term dangers linked with excessive amounts of alcohol consumption. You can get liver cirrhosis, or seriously scar your liver tissue, because it gets damaged and doesn't work as well trying to process so much toxin for so long.

Scientists also think a lot of ethanol in your bloodstream can put stress on other tissues in your body too leading to inflammation, interfering with normal hormone levels, and making it harder for your cells to repair their DNA, all of which can increase the risk of developing certain cancers. And even though alcohol doesn't kill brain cells, too much alcohol can also have long-term effects on the brain. There's some evidence that consistently drinking alcohol as a young teenager can impact the growth and maintenance of connections between neurons, sometimes leading to learning and memory problems.

Alcoholism is a physical dependence on alcohol, characterized by cravings for booze and the inability to stop drinking once you've started. Scientists also think too much ethanol in the bloodstream over a long period of time could prevent our intestines from properly absorbing thiamine, or vitamin B1, and make it harder for our livers to store and use it, too. A thiamine deficiency can lead to Wernicke-Korsakoff Syndrome which is associated with the damage or shrinkage of several brain regions, and causes a lot of problems in movement, memory, and vision. So a lot of really serious, unpleasant stuff.

Alcohol has a lot of effects on the human body, and because it's a toxin, drinking too much can lead to some serious health concerns. But in moderation – around one or two drinks per day – it's considered to be fairly safe. So drink responsibly, friends.

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