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Uploaded:2013-12-17
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What happens when your senses come into conflict with each other? In this episode of SciShow, Hank talks about motion sickness: why we have this nauseating experience and how we can avoid it or treat it.
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Sources:
http://www.livescience.com/33771-animals-seasick.html
http://www.popsci.com/science/article/2012-12/fyi-what-causes-motion-sickness-and-how-do-you-cure-it
http://well.blogs.nytimes.com/2013/09/23/rethinking-motion-sickness/?_r=0
http://www.scientificamerican.com/article.cfm?id=motion-sickness-treatment
http://adventure.howstuffworks.com/seasickness1.htm
http://www.nytimes.com/2007/08/21/health/21real.html
http://vestibular.org/understanding-vestibular-disorder/human-balance-system
Hank Green: You know I travel a lot and although I love visiting new and old places, sometimes getting there is less than pleasant. Why? Because I get carsick and airsick and seasick and horsesick and one time I did, like, stand up paddle boarding and I got stand up paddle boarding sick. And spending three hours on a turbulent flight squished between two strangers while concentrating on not puking on them is not fun, but it does help me to understand my affliction, so let's talk about that.

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Motion sickness is all about sensory conflict, meaning your central nervous system is receiving conflicting information from your eyes, your inner ears, the sensory receptors in your spine and joints. Normally these systems work together to give us our sense of balance. When you walk down the street without falling down, your vestibular system in your inner ear is jiving with the images that you're seeing with your eyeballs. The vestibular system is a sort of pretzel-shaped set of tiny sensory organs nestled in the cochlea in your inner ear. Together, these organs form a sort of human gyroscope by detecting both linear, that is forward and backward, and rotational movements of your head. But say you're riding down a bumpy road and you're squished in the back of a station wagon, your eyes say that you're stationary because they see that your seat isn't moving, but your inner ears feel every turn of the road and soon your brain is mad at you.

We're not exactly sure why those conflicting senses make you want to throw up your stomach contents, but researchers think that it's related to particularly vindictive neurotransmitters that light up your brain's vomit center. Yes, you have a vomit center. Because certain medications like those containing antihistamines and anticholinergics, and serotonin seem to relieve motion sickness symptoms scientists suspect that the nausea is related to the release of those corresponding neurotransmitters the different meds specifically target: histamine, acetylcholine and serotonin. And there seems to be a specific kind of nausea related to movement too, because drugs used to curb say the nausea created by chemotherapy don't work for motion sickness, indicating that different neural pathways are in action.

About 30% of the population is lucky enough to be naturally immune to motion sickness, though researchers aren't sure why that is. Unfortunately for the rest of us, it is a problem that can only be treated, not cured. It helps to sit up front if you're in a car so you can anticipate motions, which helps your senses all get on the same page, and though it's tempting to close your eyes as you meditate on not hurling, it's better to try and keep them open and focused on a point in the distance. Of course you can't really do that if you're on a boat at night or stuck in the middle of a jumbo jet, in which case bring some Dramamine and keep your barf bag handy.

Actually, several studies have shown that taking powdered ginger before sailing on rough seas or being strapped into a whirling test chair was equally, if not more, effective at preventing motion sickness than various over-the-counter medications. Again, why is not entirely clear, but at least one study suggested that the active compound 6-gingerol, which is related to the chemical that makes chili pepper spicy, helps keep food moving through a distressed gastrointestinal system, rather than building up in the stomach, where it's tempted to evacuate via vomiting.

And if you're wondering, yes, other non-human animals can get motion sickness too. There are lots of historical accounts of horses getting sea sick on ocean voyages and perhaps you've had to give your dog or cat their own special medication to get through a cross country road trip.

Now obviously animals, including us, did not evolve to ride in vehicles, but one theory for why we have developed such strong reactions to feeling disoriented may have to do with poison prevention, specifically a defense against neurotoxins. Because before any of us were riding around in boats or wagons, the main time our senses would get all wonky was when we'd eaten a poisonous plant or something. Feeling motion without seeing it may make the brain think that it's hallucinating, indicating that something is seriously wrong and vomiting is the body's way to expel that supposed toxin.

But until your body and brain can get together and realize that rough roads don't mean that you're on some kind of hallucinogenic trip, I'd recommend a pocketful of ginger or some Dramamine.

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