We all know the typical “signal” of a heart attack is shooting pain down one arm (there are others, but this seems pretty common). So, what is the evolutionary benefit of this? Why not severe chest pains without the arm pain? I agree with evolutionary theory that desirable traits survive, and undesirable ones don’t.
About all I can come up with is that, in the early Days of Man, that the REALLY severe attacks centered the pain in the chest, and the victim died. Those less severe had arm pain, did something (chewed on the bark with aspirin in it?), and lived.
I put this in GQ, cause I think there might be a real, scientific answer, but if the Mods feel inclined, IMHO was my other choice.
By the time you’ve managed to ingest enough cholesterol and fats to manage a heart attack, you’ve done pretty much all the reproducing you’re going to do. At this point, to make the kind of animistic metaphor that purists hate, evolution has pretty much lost interest in you.
And the shooting pain down the arm isn’t so much a signal as a side effect. Probably because there’s a nerve plexus and signals from the cardiac muscles get interpreted as pain in the arm.
Now there are other kinds of pain that don’t make a lot of sense from an evolutionary point of view, for example, seasickness, vertigo, or nausea from shock after being wounded. And from an evolutionary point of view, the answer might just be that they didn’t hinder people from breeding often enough to get bred out of the race.
Apparently during formation of the human foetus the heart is located very close to where the arm will form and the nerves in the area remain cross-connected in the brain.
This is called referred pain IIRC.
Hope someone can make things a little clearer than I have done.
it is called refered pain, yes…basically the innervation of the nerves into the chest and gut are not highly devloped, so the pain comes across as something different.
per A&P at unm
Referred pain is caused when the sensory fibers from an internal organ enter the spinal cord in the same
root as fibers from a dermatome. The brain is poor at interpreting visceral pain and instead interprets it as pain from the somatic area of the dermatome.
So pain in the heart is often interpreted as pain in the left arm or shoulder, pain in the diaphragm is interpreted as along the left clavicle and neck, and the
“stitch in your side” you sometimes feel when running is pain in the liver as its vessels vasoconstrict.
That’s a new one on me. I’ve heard it’s from the ligaments attached to the diaphragm going into spasm. I’ve never read this theory before. I’ve always believed it’s a spasm and the most likely explanation is that it is a spasm of the diaphragm ligaments.
You mentioned some cryptic site (A&P at unm). I don’t know what that is. Do you have a link?
While heart attack is the best known example of “referred pain”, it’s far from the only one.
I’m at particularly high risk of ectopic pregnancy, and have always been told to get myself to hospital STAT if I ever develop pain in my shoulder during early pregnancy.
Ligaments shouldn’t spasm, they have no muscle tissue. I’d been taught, and still believe that it comes from spasm of the intercostal muscles (between the ribs). Possibly it could be spasm at the site of the chest wall and diaphragm, where ligaments attach, tho. I’ve never heard the liver vasospasm theory. If that were true, I’d expect to hear about cases of liver infarction in runners. But this is all educated guesswork on my part, I can’t find the info on my academy’s website.
I hope kinoons comes back with that link. Now I’m curious. I hate when that happens!
I’ve heard that cramping is due to stretching of the liver capsule. The explanation goes as follows:
In the untrained runner, blood return to the heart marginally exceeds its pumping capacity. This generates a small (but acute)increase in pressure in the inferior vena cava. Because of the anatomical relationship of the heart, liver, and inferior vena cava, the increase pressure is “felt” by the liver. With increased pressures, the liver swells slightly, resulting in stretching of its pain sensitive capsule and ouch, cramping.
I know of no experimental verification of this hypothesis, so take it with a grain of salt.
I used to get side “stitches” while running (even after I’d run for many years), and they often occurred on the opposite side from my liver. BTW, I stopped getting them after I gave birth. My personal theory is that I stretched out my diaphram while pregnant.
Side stitches usually occur on the right, just below the diaphragm, however, they occur on the left in some people, so liver theories can be discounted. I used to get them (on the right) even after running for years, but only when racing. It seems to happen to even experienced runners if they are attempting to run too fast for what they have conditioned their bodies. Since now that I don’t race as fast, I don’t get them any more.
I’ve read many diffeent theories on why they occur. I said diaphragm ligaments, but as Qadgop the Mercotan pointed out, it’s impossible for a ligament to spasm. What I actually read, and what he suggested, is the attachment of the diaphragm to the rib cage. I just assumed that the attachments are by ligaments, which is apparently not correct. The diaphragm, apparently, has a longer connection on the right than the left, so the stitch usually occurs on the right, but not necessarily.
I believe improper breathing is the culprit. I used to breathe a lot more shallow than I do now. Perhaps it has something to do with trapped air. I don’t know, and neither does anyone else. I remember once while running a marathon that I noticed my shoelace was untied. I was also having a slight stitch at the time. I stopped, bent over, and tied my shoelace. My stitch disappeared. It may have something to do with the expelling of air that was trapped.