Wikipedia:Reference desk/Archives/Science/2019 November 26

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November 26

What kind of innervation does human heart have?

Does heart has innervation to the SA node only for influence on the rhythm only (sometimes) and not for pain sensation, or it has innervation inside it for pain sensation too? Theoretically, if a physician cut an heart of his patient without any anesthesia. Should the physician expect for pain from the heart? (assuming the the patient doesn't have any other pain, for example because it section were done by catheter or by local anesthetic for the opening of the chest). If it doesn't have innervation, so why people with MI feel so strong chest pain as if it the most innervated? 93.126.116.89 (talk) 06:19, 26 November 2019 (UTC)

Angina may explain. ←Baseball Bugs ^{What's up, Doc?} carrots→ 08:08, 26 November 2019 (UTC)

The electrical conduction system of the heart (which includes the SA node) only makes the heart beat, by producing the action potentials that make the heart contract. In general throughout the body, there are separate afferent and efferent nerve fibers; afferent fibers transmit stimuli from the body to the central nervous system, while efferent fibers transmit from the CNS to the rest of the body. The heart does have efferent innervation, but this only serves to regulate the heart rate up or down. The heart itself generates its own action potentials. The heart has afferent innervation as well, and this is what transmits pain sensations to the brain. These nerves are separate from the heart's conduction system. Note that heart attacks don't always produce the "traditional" symptom of chest pain, and also, because the sensations are poorly "mapped" in the brain, pain from the heart can be referred to other parts of the body. --47.146.63.87 (talk) 08:18, 26 November 2019 (UTC)

Immune system and antimicrobial resistance

Why pathogens (fortunately) do not develop resistance to human immune system as quickly and intensely as to antibiotics? It seems that as they encounter immune system more often than antibiotics, the evolutionary pressure would be even greater. Also, since antimicrobial resistance states that it "threatens the world as we know it, and can lead to epidemics of enormous proportions", would immune system effectively offset the threat? 212.180.235.46 (talk) 22:09, 26 November 2019 (UTC)

Because any chemical that kills pathogens without killing the person taking them is necessarily less effective than the person's own defenses, which are alive and which adapt to new pathogens. See Immune system. --Guy Macon (talk) 00:02, 27 November 2019 (UTC)

I would say that is wishful thinking. The real reason pathogens don't develop resistance to immune systems is that a pathogen that kills its hosts before the hosts can spread the pathogen is selected against. Consider these counterexamples: Anthrax is quite lethal but avoids this problem by being non-contagious. Instead, it forms spores in the carcasses of its dead hosts and hopes to spread that way. Rabies is 100% fatal, and avoids the problem by getting its hosts to salivate, and bite new hosts. Abductive (reasoning) 09:40, 27 November 2019 (UTC)

You should tell this to the people who died of AIDS. HIV is known to quickly develop resistance to any immune responses eventually exhausting the immune system and killing its host. Ruslik_Zero 11:00, 27 November 2019 (UTC)

We're getting off track with the HIV and Rabies, since they are viruses. But note that HIV does not kill its hosts quickly. Abductive (reasoning) 11:57, 27 November 2019 (UTC)

Whether we're getting off track depends somewhat on the OP I guess. They asked about antimicrobial resistance but then seemed to talk about antibiotic resistance. As per the article, antimicrobial resistance is a broader category than antibiotic resistance. The article indeed talks about antiviral resistance including HIV Antimicrobial resistance#Viruses. I admit I found this a bit weird at first since of course in a strict biological sense viruses are often not considered microbes nowadays as they are not generally considered living. But it seems to be the same as the WHO [1] and the NZ MOH [2]. Possibly they consider it doesn't make sense to put viruses in a special category for monitoring etc and microbes is the best fit. (And indeed as our article mentions, viruses are normally studied as part of microbiology.) True the US CDC seems to use the term interchangeably with antibiotic resistance [3] like the OP. But then again they do track both fungal and bacterial resistance under this and specifically mention they don't include viruses or parasites in their report suggesting they don't think it's obvious [4]. And they do include viruses in the papers they list [5]. (And elsewhere they call viruses microbes [6].) It's true of course that antiviral resistance is not any where as much as a threat as antibiotic resistance or even antifungal resistance, but that's a different point. And on that point, while I didn't read the WHO report where the OP's quote came from, I strongly suspect they probably were at least concerned about anti-fungal resistance and probably anti-parasite resistance and not just antibiotic resistance. Nil Einne (talk) 13:29, 27 November 2019 (UTC)

This is a good question! The immune system has a diverse arsenal to attack pathogens: from antibodies to the complement system to the respiratory burst and more. It's harder for a pathogen to develop resistance to a bunch of things than to one. For instance, some bacteria develop resistance to penicillin by acquiring a modified penicillin binding protein that isn't inhibited by penicillin. For this reason, there is increased use of multi-drug regimens, such as co-amoxiclav, trimethoprim/sulfamethoxazole, and the regimens for tuberculosis and malaria. With that said, some pathogens do have a good ability to resist the immune system; examples include some Salmonella, Helicobacter pylori, and the aforementioned tuberculosis and malaria pathogens. Logically, if no pathogens could withstand the human immune system, no one with a healthy immune system would die of infectious disease or develop a chronic infection. There's a constant evolutionary arms race between disease-causing organisms and the organisms they infect. --47.146.63.87 (talk) 09:36, 27 November 2019 (UTC)

First, resistance to many classes of anti-microbials have existed in the nature for millions years. Bacteria only need to acquire necessary genes, which can be easily done by multiple routes. So, nothing to develop in the first place. Second, bacteria do develop or acquire resistance to immune responses. One notable example is acquisition of toxin genes (or other virulence factors), which are used as chemical weapons against cells of the immune system. Bacteria can also avoid expressing some proteins, which serve as targets for the immune system. One example is appearance of strains of Bordetella pertussis that lack pertactin protein, which is used in acellular vaccines. Ruslik_Zero 11:18, 27 November 2019 (UTC)

The immune system is more like a weapon factory than a weapon, and it takes no prisoners, even attacking the body cells. For instance, it can produce an infinite range of antibodies, and if a pathogen develops resistance to one though changing antigen, it creates a new pattern for which the immune system could very well be already ready. This is obviously harder to fight back that a single specific molecule. Gem fr (talk) 04:29, 29 November 2019 (UTC)