Note: I am not la looking for medical advice. Do not remove my post.
I had a terrible stomachache last night and ended up in hospital. I threw up once at home and I only puked the food I had eaten 20 min before. Later at the hospital I threw up what I had eaten for lunch. Why the first time I didn’t threw up a mix of both. How does the stomach selects what to throw up?
My wife always says that the body is wise and only expels what hurts you. Kinda right to think that way but how does it work.
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The stomach really doesn’t ‘know’ what is causing the upset. There also aren’t any compartments that hold different meals. It’s basically one big mixing bowl (or rather, a bag) that gets mixed and mashed by muscles. What likely happened is, the stomach got upset (either by something you ate or an entirely different cause) and stopped mixing properly. Maybe lunch was compacted a bit more, so initially dinner came out more easily.
I like your wife’s answer, but:
It doesn’t really select what to throw up, but more, gets signals that maybe something bad has just entered your body from your digestive track. Best to eject.
This response is triggered by the brain, usually after being signaled by nerves connected to different things: Sensors for specific chemicals or other input from your guts (what you ate was not “safe”). Your balance system (issues with this can be a sign of ingested toxins, hence why messing with your vestibular system induces vomiting). Stress chemicals. And, stimulation of specific regions that might indicate a (potentially life-threatening) blockage, such as the back of your throat before it branches into your lungs.
Think of the various situations in which vomiting occurs: you’re sick, you ate something bad (food poisoning), you have vertigo, something very stressful occurred, you had chemotherapy, you just had surgery. My wife threw up her salmon dinner when she went into labor. There was nothing wrong with the salmon. After my grandmother’s funeral, I threw up in the bushes. There was nothing noxious that needed to be expelled.
What these scenarios have in common is that chemicals in the body were released that were picked up by one of four “vomiting centers,” which are nerves that detect these chemicals. They create the sensation of nausea (sometimes with stress there is no nausea – you just vomit) and set in motion the muscular contractions that cause you to vomit. For example, nerves in the tube-like structure of your intestines may detect toxins in food you just ate. Nerve impulses go straight to your brainstem, via the vagus nerve. Or the intestines may respond to something noxious and release chemicals that circulate in your blood and reach a vomiting center in your brainstem. I remember a story of a baseball player who accidentally swallowed some chewing tobacco juice and starting puking during a game, and another player in the outfield saw this and started puking in response. Player #1 vomited because of his body’s detection of something noxious, and player #2 vomited because his brain “saw” something disgusting. So there are multiple areas in our body that can set off vomiting. They all send neural signals to a part of our brainstem that coordinates all the actions involved in vomiting.
It doesn’t know, it just knows there’s irritation and kind of freaks out and starts tossing stuff out.
It won’t necessarily get everything in the first go, so if it’s still irritated, it may happen again, expelling even more
Sometimes this is triggered even when your stomach is basically empty, because all it knows is it’s irritated, so it may keep going even after it expelled the bad stuff
It’s like having an itch, which compels you to scratch it. You don’t really necessarily know why the itch is there, you just scratch and hope it works, and if it’s still itchy afterwards, you may keep scratching more. It’s possible the original cause is gone, but now it’s all irritated and may continue to itch for a bit
You wife’s answer is sweet, but our stomach’s are dumber than that
It’s a communication between the immune system, the nervous system, and the gut. If the toxin is biological based, like a foodborne toxin, the immune system employs a certain kind of white blood cell that releases substances that tell your gut to contract and expel. This causes vomiting.
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