Why Do We Vomit?


Roller coasters. Bad sushi. Public Speaking.
All things that make you puke. But why? Hey guys, Chastity here for DNews. We’re gonna be tackling your science questions
every Monday. This week’s viewer question comes from Sam Litsas, who asks, “How/why
do we vomit?” Great question, Sam. Unfortunately, there’s
no short answer to why we puke. As I’m sure you’ve all experienced, vomiting
is an involuntary expulsion of your stomach contents through your mouth and sometimes
your nose. Ick. Even though it’s gross, it’s actually
a good thing! Because vomiting defends you from being poisoned. The part of the brain
that manages poison control is called the area postrema. This part is exposed to the
bloodstream, allowing it to scan for toxins. When a toxin is spotted, like as a result
of one too many tequila shots, the area postrema tells the body to purge the stomach. When you vomit, several things happen to your
body at once. Your blood moves to your internal organs, causing your face to lose color. Your
teeth are coated in saliva to shield them from your stomach acid. You break a sweat,
your blood pressure drops, your heart races, and you start to breathe faster as you retch.
The large muscles of your respiratory system reverse the path of your digestive tract,
turning you into a human geyser. It’s uncomfortable, involuntary, and a big ol’ mess. But it’s
also a unique ability! Other than humans, there are only a few animals
that can vomit, like cats and dogs. Mice and other rodents, however, can’t. Neither can
horses. Rodents lack the key neural circuits that tell the stomach to purge. They also
have a powerful seal that separates the esophagus and the stomach, which cannot open. That explains
why rat poison is so effective. Horses also have a strong band of muscle around
the esophagus. It operates as a one-way valve as it enters the stomach. Food can go down
into the horse’s stomach as this valve relaxes, but the valve squeezes down on the opening,
preventing food from going back up. So why do people vomit? The list of causes
is lengthy: Drinking too much alcohol, Prescription and nonprescription drugs, Food
poisoning, or viral infections that inflame your gut and cause severe stomach pain. Throwing
up can also be triggered by your stomach’s nervous system telling you it’s too full. Feeling afraid or disgusted can also make
us nauseous. If you’ve ever puked during a gory movie or at the sight of blood, it’s
because the unpleasant visuals stimulate nausea. These visuals cause the limbic system in your
brain, which controls emotions, to feel distressed. This distress causes the autonomic nervous
system, which controls internal organs, to tell your stomach to purge. So even though
you’re not really exposed to a life-threatening poison, your body has a hard time differentiating
emotional and physical stress. In either case, it reacts the same way. One of the things that makes me nauseous is
air travel. Why does flying make us feel sick? Julian answers that in this video.

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