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Anyone who’s frequently around kids knows that they throw up a lot, and at seemingly weird times. But there are some interesting biological reasons why that might be!

Hosted by: Hank Green

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Sources:
https://academic.oup.com/bja/article/69/Supplement_1/2S/255922?searchresult=1
https://www.npr.org/sections/health-shots/2018/09/10/645723728/the-queasy-truth-about-why-kids-are-so-prone-to-vomiting
https://gut.bmj.com/content/gutjnl/45/suppl_2/II6.full.pdf [PDF]
https://onlinelibrary.wiley.com/doi/abs/10.1034/j.1398-9995.2000.00118.x
https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1748-1716.1973.tb05472.x
http://denhamlab.gmu.edu/Publications%20PDFs/Denham%202007.pdf [PDF]
https://www.webmd.com/parenting/features/anxiety-stress-and-stomachaches#1
http://journals.sagepub.com/doi/abs/10.1177/1948550613511499
https://www.sciencedirect.com/science/article/pii/S0306453010002155
https://onlinelibrary.wiley.com/doi/pdf/10.1002/j.1532-2149.2012.00169.x
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2658708/
https://www.physiology.org/doi/abs/10.1152/physrev.1994.74.1.95
https://books.google.ca/books?hl=en&lr=&id=s7nWIlnimY8C&oi=fnd&pg=PA65&dq=autism+emesis+emotion&ots=85qGSCHzQg&sig=prhPMLSl8ooH8L5KM0pJRDNku50#v=onepage&q&f=false

Images:
https://commons.wikimedia.org/wiki/File:Afferent_(PSF).png
https://commons.wikimedia.org/wiki/File:Gray793.png

 introduction


(0:00)-(0:52)  If you're a parent, a school teacher, or anyone who's frequently around kids, you probably know that kids throw up a lot.  And at seemingly weird times.  Yes, kids have developing immune systems, so they do tend to catch more stomach bugs.  But many times, there's more to it than that.  Turns out, kids bodies are just a little more aware of just what's going on in the outside world or inside themselves.  Biologically speaking, vomiting is triggered by groups of afferent neurons, nerves that bring information to your brain and spinal cord.  In both kids and adults, these nerves can be activated by multiple things, from chemicals to pressure to motion.  But children's afferent neurons are more sensitive to input, and their brains are still learning to regulate their bodily processes.  That ultimately means that their threshold for throwing up is lower.  And that can show up in a few ways.

 why kids vomit so much


(0:52)-(2:27)  For example, stimulating the vagus nerve, which among other things connects the heart and brain, has been shown to trigger nausea and vomiting in adults.  So if that nerve is more sensitive in kids, it might explain why those heart-recing games of tag or hours on a bouncy castle can lead to messy results.  That kind of stimulation might be normal for grown-ups, but in children, it could be enough to ultimately activate the vomiting reflex.  another reason kids might puke is because they're still learning to be aware of their emotions and can easily become overwhelmed.  In childhood, the emotion centers of the brain, like the hippocampus and amygdala, are still forming connections with eachother.  But even before that's finished, they're already connected to parts of the brainstem that start the vomit reflex.  That means their brains might misinterpret emotional signals, like intense fear or joy, as sickness and trigger vomiting when it is not really needed.  Along with that. kids also typically have a harder time expressing their feelings, which could lead to a buildup of adrenaline and the stress hormone cortisol.  And some studies suggest that, too, could make them feel nauseous or get sick.  A final thing that might lead to all this vomiting is that kids have a lower pain threshold.  According to research, nausea and pain inside the body, also called visceral pain, share some nerve pathways, and scientists even think one sensation might influence the other.  Since children have a lower pain tolerance to start with, pain signals coming from near the stomach might be misinterpreted by the brain as nausea and bring on vomiting.  That's why getting hit in the stomach with a soccer ball might leave a kid winded, or they might puke.  Meanwhile, an adult with a higher pain threshold might not be as bothered. 

 data collection


(2:27)-(2:58) Now, one caveot to all these explanations is that they mostly lack experimental evidence.  Mainly because no one wants to make a kid throw up.  Instead, we rely on correlations or, occasionally, case studies of children who are already sick, like ones who just got an operation.  The good news, though, is that even if there are tons of reasons kids barf a lot, most of the time, it's nothing to worry about.  Pediatricians say to watch out for anything in the vomit that's not supposed o be there, like blood or bile.  But otherwise, a good hug and some water go a long way. 

 thanks to all our Patrons


(2:58)-(3:18) Thanks for asking and thanks to all our patrons on Patreon who helped us make this episode!  If you want to help us keep making episodes like this and support free science education online,you can go to patreon.com/scishow.