How does nausea work?

[gib65]

What happens in the stomach to trigger the nausea sensations we feel when we consume things that we shouldn't be consuming. There must be a layer of something coating the stomach walls, something that protects it from stomach acid, and when we consume things like alcohol or any kind of foriegn substance we're not used to, it somehow eats away at this layer, and once the actual stomach walls are exposed, the stomac acid starts eating away at this layer, triggering the nausea reaction.

 

Am I right... or way off?

[Cap'n Refsmmat]

Often times it's a side effect of other problems. For example, motion sickness (at least, in my understanding of it) is due to a lack of correlation between visual cues and the inner ear, so the brain believes that it may be being poisoned and promptly vomits up any possible toxins.

Aha:

Humans have developed motion sickness as a defence mechanism. The area postrema is a small part of the brain responsible for inducing vomiting when poisons are detected, and for resolving conflicts between vision and balance. When aboard a ship with no windows, one's inner ear transmits to the brain that you are in motion, but the eyes tell the brain that everything is still. The area postrema will always believe the inner ear signal over the eyes, as the eyes are more susceptible to trickery (see optical illusion). Thus, the brain will come to the conclusion that one is hallucinating. It will further postulate that there is a hallucination because of poison ingestion, and so will attempt to rid of the poisons by inducing emesis.

[ecoli]

Often times it's a side effect of other problems. For example' date=' motion sickness (at least, in my understanding of it) is due to a lack of correlation between visual cues and the inner ear, so the brain believes that it may be being poisoned and promptly vomits up any possible toxins.

Aha:[/quote']

 

Which, if you think about it, you could see as being a great evolutionary advantage. Especially when testing new/ unknown plants for edibility.

[Sisyphus]

Do a lot of poisonous plants cause inner ear problems?

[Bluenoise]

It doesn't have to involve the inner ear. It can often be the rest of conflicts between two different sence.

[gib65]

Well, that would explain what's happening in the brain to induce nausea, but I'm wondering what happens in the stomach. Does it result from the stomach lining getting eaten away?

[ecoli]

Do a lot of poisonous plants cause inner ear problems?

 

not inner ear problems... plants could contain poisons that cause hallucinations or nausea.

[Cap'n Refsmmat]

Well, that would explain what's happening in the brain to induce nausea, but I'm wondering what happens in the stomach. Does it result from the stomach lining getting eaten away?

I doubt it - that would probably result in an ulcer.

[gib65]

I doubt it - that would probably result in an ulcer.

 

Well, something must be happening.

[DaveC426913]

What happens in the stomach to trigger the nausea sensations we feel when we consume things that we shouldn't be consuming. There must be a layer of something coating the stomach walls, something that protects it from stomach acid, and when we consume things like alcohol or any kind of foriegn substance we're not used to, it somehow eats away at this layer, and once the actual stomach walls are exposed, the stomac acid starts eating away at this layer, triggering the nausea reaction.

 

Am I right... or way off?

The stomach has a mucous layer, yes. But if it is stripped away, you get an ulcer. What happens with undesirable substances is that the stomach absorbs them through its lining and through the mucous layer. 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.

 

In the case of alcohol, this is not stomach-related. It is the body sensing an imbalance internally. Alcohol messes up the body in a lot of ways - probably because it is chemically much like water. The inner ear (the cochlea), when its fluid gets diluted by alcohol, the hairs that sense movement and balance don't operate properly because alcohol is lighter than water.

[husmusen]

Vomiting is basically a form of reverse peristalsis with violent contractions of the stomach. That is the body flips a 'reset switch' to make food go the other way for a bit.

 

It's controlled by the Medulla(a part of the brain).

 

The Medulla takes signals from all around the body, so irritation of the GI tract can cause vomitting, but sensations from the inner ear can also cause it. As can vagal nerve stimulation(I think) and emotional stimulii.

Also chemoreceptors in the nose and mouth can trigger vomiting, generally the ones affiliated with bacterial pocesses.

So rotting fish, fermented blood, feaces, can all trigger vomitting.

Rotting human flesh has a very pronounced vomiting effect.

 

Some Chemotherapy drugs are really really good at stimulating the Medulla

 

Put simply the way I understand it is that the Medulla processes signals from all over the body, and tries to figure out if you have ingested a toxin. If it decides you have it tells you to hurl.

 

I would also infer that the liver has some means to trigger vomiting as well, although I don't recall them teaching us that.

 

Regards

Husmusen.

[SkepticLance]

On the subject of motion sickness ...

Vertigo is one of the most common immediate effects of poisoning when a toxin is ingested. Evolution has equipped us with the response of nausea and hence vomiting when we feel vertigo.

 

I had this hammered home personally when I suffered a minor case of decompression sickness (the bends) with a bubble in the inner ear. I began with incredible vertigo. Within two minutes I was spreading my lunch across the ocean, even though the boat I was on was in totally calm water.

 

With motion sickness, as previously mentioned, it is a discrepancy between visual cues and inner ear cues that leads to vertigo. The nausea is caused by the vertigo, not by the motion.

 

As husmussen said, these effects are actually mediated by the brain. Lots of stimuli lead to vertigo, and hence nausea.