DRD_85 t1_ixezx62 wrote on November 22, 2022 at 11:00 PM

Reply to comment by WorldwidePies in When a person gets stomach flu (viral gastroenteritis) or food poisoning, what exactly is happening in the body that causes stomach cramps? by geekonthemoon

Great post and explanation!

However, I would like to discuss the last sentence. Wouldn't you agree that "Vomiting the microorganisms and their toxins is a protective mechanism that helps prevent the passage of theses substances to the small intestines...." is not necessarily a protective mechanism in animals but is, in reality, a mechanism evolved by microorganisms to facilitate their spread in the environment?

I would argue that animals evolved the vomiting reflex to deal with toxic and irritating chemicals found in plants and the environment in general. My evidence would be that the vomiting reflex is controlled by our own endogenous serotonin and 5HT-3 receptors. If we ingest an irritating chemical, the inflammatory response causes an acute release of serotonin in the gastro tract which can lead to activation of the 5HT-3 receptors and vomiting.

When it comes to microorganisms, some have evolved proteins over time that can also bind to and activate the 5HT-3 receptor directly.

However, I will concede that infection by microorganisms themselves can cause localized gastric irritation (by way of activation or our own immune system) which can lead to release of gastric serotonin. But, again, this inflammation is just a localized immune response....same thing that could happen with an irritating chemical from a plant.

In the case of vomiting directly from the toxins produced by microorganisms, I still say that is not a protective mechanism. The human body does not "know" it has been invaded by a toxin, so it therefore is not itself activating the vomiting reflex spontaneously because of the toxin. The toxin is literally binding to the receptor that activates the vomiting center.

I suppose it's a bit of which came first...the chicken or the egg.

WorldwidePies t1_ixk0a4e wrote on November 24, 2022 at 12:36 AM

I would not agree that the vomiting reflex doesn’t protect the animal. Clearly, the sooner the irritating substances are cleared of the gastrointestinal tract, the better for the animal’s health. The animal doesn’t have to « know » anything to be protected by a reflex, just like taking your hand off the hot stove protects you before the brain event feels the heat.

I would also not agree that the vomiting reflex of animals was evolved by the microorganisms, because that’s not how evolution works. The development of the sensory apparatus needed to sense the irritation, and then to provoke the necessary contractions to induce the vomiting is the result of the animal (not the microorganisms) population’s genetic changes and selection, with the animals that developed that reflex being fitter to face off infections.

I’ll agree that some microorganisms may have evolved to produce increasingly irritating substances so as to provoke vomiting with evermore efficiency because this could benefit them with the dispersion aspect.