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How does the stomach know to vomit?

  1. Sep 16, 2006 #1

    DaveC426913

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    Asked in
    http://www.scienceforums.net/forums/showthread.php?p=302767" [Broken].

    By what mechanism does the stomach recognize the ingestion of things we shouldn't have eaten and initiate reverse peristalsis (vomiting)?

    (There's the whole issue of inner ear and brain processes that deal with nausea, but that's a separate issue) What happens in the stomach?
     
    Last edited by a moderator: May 2, 2017
  2. jcsd
  3. Sep 16, 2006 #2

    arildno

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    Dearly Missed

    I would prefer not to know..:yuck:
     
  4. Sep 21, 2006 #3
  5. Sep 22, 2006 #4

    DaveC426913

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    Thanks, these are good links. Although they do not address my question. I am curious not so much about how the brain decides to vomit, but how the stomach senses something's wrong - that's a phyiscal or chemical thing.
     
  6. Sep 22, 2006 #5

    DaveC426913

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    Oh yeah, it's coming back to me now.

    The stomach absorbs things through its lining. If it detects bacteria or poisons, it will attempt to protect itself by releasing fluid and by increasing the mucous lining. If it continues to experience assault, it triggers the brain to vomit.
     
  7. Sep 22, 2006 #6
    The thing is, the stomach, or any organ, doesn't "detect" anything independent of the brain. Things are "detected", that is "sensed" by nerves with specialized receptors, and all those nerves are essentially extentions of the brain. By the same token, the stomach doesn't trigger the brain to do anything. The brain does the sensing and computing and then initiates the muscle contractions of vomiting.
     
  8. Sep 22, 2006 #7

    DaveC426913

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    This is not true. The body is rife with automatic defensive actions without any involvement from the brain. Clotting, swelling, white corpuscle attacks, opening fluid floodgates, etc. Killer diseases in 3rd world countries are caused by the fact that the intestine, when it is assaulted by bacteria, open the floodgates of fluid, causing diarrhea, resulting in death by dehydration. No brain involvement at all - straight chemistry in the intestine.
     
    Last edited: Sep 22, 2006
  9. Sep 22, 2006 #8
    All this is true. The issue I had was with the term "detect". You notice I brought the synonymous term "sense" into the picture. When you speak of the stomach as "detecting" anything it erroneously implies the stomach has a kind of self contained consciousness and sensory system, especially since you went on to ascribe to it an ability to initiate a triggering of the brain.

    The stomach you describe here seems to have too much self-monitoring and decision making ability. In other words, I am picking on the way you've anthropomorphised it.
     
  10. Sep 22, 2006 #9

    Pythagorean

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    Yeah, even your muscles have a sort of memory and calculation sensor system, it's all lower level nervous system. That's how people get good at martial arts, snowboarding, shooting hoops, etc by repetition. Your muscles can actually detect acceleration. Trust me, your brain already knows what it's trying to do for the most part.
     
  11. Sep 23, 2006 #10
    What's this called? Got a link?
     
  12. Sep 23, 2006 #11
    The vomit action is still controlled by the brain, the area of the brain, which gets the vomit ball rolling is actually called the vomit center. Its located in the lateral medullary reticular formation in the medulla. On the ventrical there is chemoreceptor trigger zone, stimulation of which will make you vomit. The chemoreceptor is sensitive to toxins and poisons in the blood stream.
    Neural activation happens as a result of information coming directly from the frontal lobes of the brain, the digestive tract and the inner ear.
    When the vomiting center in your brain senses a problem it initiates the vomiting sequence. Sends a message for the windpipe to close and the abdominal wall and diaphragm muscles tighten suddenly and forcefully....then you vomit.
    The stomach its self is very relaxed at this stage, the muscles around it do all the work.
     
    Last edited: Sep 23, 2006
  13. Sep 23, 2006 #12
    It alarms me a little bit that you actually have to have poisons in your blood before the brain decides it's time to throw up.

    So this leads me to wonder about food poisoning, which I've had several times. I've been under the impression it's bacterial, but I don't exactly know what the bacteria are doing that makes you sick. Is it that they release toxins?
     
  14. Sep 23, 2006 #13
    Yes nearly all bacteria pathogens synthesize toxins. Because they are growing in numbers by the minute. It wants to take over your body as its own person breeding ground. Depending on the person and type of bacteria it may take 2 hours and up to 10 hours befor you become ill. Once the levels become high enough, it will cause the brain to signal the body to get rid of it..out one end or the other.
     
    Last edited: Sep 23, 2006
  15. Sep 24, 2006 #14

    DaveC426913

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    Yes, this was not in dispute. What I was after was how the stomach "knew" it was under attack in the first place.

    What you're saying is that he stomach does not know, that anything that's going to cause vomiting must first enter the blood stream and reach the brain?

    See, here you imply that it is the stomach sending a signal. What is the signal saying? It must be saying that something's wrong (no matter how simplistic that signal is.)

    Additionally, surely, the stomach increases its mucous lining as a protective measure without having to involve the brain?
     
  16. Sep 24, 2006 #15

    DaveC426913

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    These are your implications.

    Note though, that all the organs are capable of sending signals to the brain.
     
  17. Sep 24, 2006 #16
    The stomach does not know its under attack, and it does NOT have decision making ability. It has no way to think for its self.
    If you try and drink a gallon of milk in a hour, the stomach become so distended, that it becomes painful. Neural activation happens then. But its still the brain giving the final comand to vomit.
     
  18. Sep 24, 2006 #17
    By what means? Give a few examples.
     
  19. Sep 24, 2006 #18

    DaveC426913

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    Let's not take words too literally. I don't mean "know" technically. Nor do I suggest organs have any decision-making ability.

    Dysentry is an opening of the floodgates in the intestines caused by bacteria. It is a direct reaction of the intestines to the bacteria. There is no brain involvement at all.

    I believe that the stomach - in addition to dumping chemicals in the bloodstream which signal the brain to vomit - also have direct defenses, such as increasing the mucous lining.
     
  20. Sep 24, 2006 #19

    DaveC426913

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    As in Hyp's post, they dump chemicals in the bloodstream. (I grant that it is debatable point whether this would be called the 'organ signalling the brain', or the 'brain sensing things around it'.)

    Anyway, see my response to Hyp, above.
     
  21. Sep 25, 2006 #20

    Pythagorean

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    the neuromuscular junction

    Here's a wiki article about muscle memory, that pretty much says what I said in my previos post

    http://en.wikipedia.org/wiki/Muscle_memory

    and if you click neuromuscular in there, you'll see a bit about the neuromuscular junction.

    edit: I don't know how vomiting works, I was just supporting someone's comment before mine that suggested the stomach may act like this, but this is an example of the brain being excluded fromt he process.
     
  22. Sep 28, 2006 #21
    Well, that whole article is about a phenomenon that is controlled by the brain, and it says so. "Muscle memory" doesn't mean the memories are a property of the muscles, it refers to the brain's control of the muscles becoming automatic, less and less consciously controlled. The brain is controlling the whole thing in all cases, it just involves consciousness less and less. These things become more like breathing: we don't have to make conscious decisions about breathing in most cases, but the brain is controling it the whole time, (as opposed to the lungs, or more properly, the diaphram, having a built in control of some sort disconnected from the brain). All kinds of autonomic functions are controlled by the brain: sweating, goosbumps, heart rate, body temperature.

    Dave was talking about the notion of organs reacting without any brain involvement. "Muscle memory" doesn't fall into that category at all.
     
  23. Sep 29, 2006 #22

    Pythagorean

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    Yeah, I guess it is still considered part of the brain, but the calculations don't take place in your higher levels, they're all lower level brain functions. But it's not the grey matter inside your skull. It's an extension of the brain that goes down your spine as I understand it (or at least is at the very bottom of your brain in back)

    My main source for this (i was just using Wikipedia to communicate it) was "The Brains of Men and Machines" by Ernest Kent, who compares the architecture of the brain to a computer.

    Basically, how he describes it is you have three major functions (input, calculation, output) and you have a number of leves. So you can think of a grid where the height is the level and the breadth is one of the three functions. Each point on the grid is a brain component related to its function and level.

    The lower set of input, calculation, and output doesn't even usually reach your head, but it can, because the lower levels can hand a job up to a higher level if it's not able to complete it, or if the higher levels ask for it (i.e., you consciously guide your hand as opposed to jerking it back from a burn)

    I was excluding the lower levels of the brain from the brain in my comments, I apologize, but as I understand it, they aren't actually in the head. The brain kind of drips down into the spine, which seems more like an extension of the brain to me.

    But that's also how our Brain's our made, so that if one chunk of it gets damaged or destroyed, the other (higher or lower) functions can take over the processes that are missing now. It's supposed to be a very good parallel processor, better than any compute (this is how you can see everything in front of you at once) but terrible and slow at series problem solving (like math, where one operation needs to be completed before you can move to the next operation)

    I don't think I consciously chose to vomit, so I assume it's taken care of on the lower levels.
     
  24. Sep 29, 2006 #23
    Well, you get my main point: the muscles don't actually have memories and don't initiate any actions themselves.

    You should be aware of the fact that terms like "higher" and "lower" are pure value judgement on the part of the classifier. I might respin them as the "perfected, automatic" functions, and the "imperfect, supervision-requiring" functions. In most of these cases "higher" and "lower" come from a time when people were even more uncomfortable about evolution than they are today and wanted to highlight what they considered non-animal about humans, and be proud of it. Someone linked to an article a few weeks ago which put forth the interesting and, I think, reasonable proposal, that consciousness only exists as a place to work processes out so they can become unconsciously triggered in the future.

    What you said here:

    "But that's also how our Brain's our made, so that if one chunk of it gets damaged or destroyed, the other (higher or lower) functions can take over the processes that are missing now."

    is pretty much not true, and I'm not sure where you got this idea. After brain damage the brain does its best to salvage what it can by shifting functions, in so far as that's possible, but it doesn't ever amount to one section "taking over" for a damaged section such that everything's OK again. Recovery, to the extent it takes place, usually means the damaged section is able to recover enough to do its own usual work again. This is common in cases where the original deficit is a matter of temporary loss of blood flow in conjunction with an injury or stroke. You won't find the brainstem taking over for a damaged temporal lobe or anything that remarkable.
     
  25. Sep 30, 2006 #24

    Pythagorean

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    I got it from the book, the "Brains of Men and Machines" and I probably paraphrased it terribly. Throughout the book he's comapring the human brain to computer brains, so I think his point was that the human brain doesn't shut down when it loses one part of it (unless, of course, it's managing our internal life support systems), it continues on without that part.
     
  26. Oct 3, 2006 #25
    PF member Rade posted this interesting link in the thread on deaf people and music which shows the kind of shifting of function I've most often read about:

    http://www.sciencedaily.com/releases/2001/11/011128035455.htm

    The whole article is worth a read, but basically it says that when the parts of the brain that would normally process hearing aren't being stimulated by the ears (because of ear damage of one kind or another) then the sense of touch will take that part of the brain over and use it for itself, in this case the aspects of touch that normally process vibration. It seems to be the case that with all this extra computing space for vibration deaf people are more sensitive to it than hearing people.

    Now, I'm pretty sure the reason touch takes that space over rather than, say, vision, is because sensitivity to vibration is probably already located adjacent to, or at least strongly connected to, the hearing center in question to begin with.
     
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