The Purpose of a "sudden faint"

Factual Questions
1

I had a co-worker last week he told me he had a cyst on his chest. He said it was hard and was bothering him. I looked at it and it was small (less than half the size of a pinky fingernail.

I told him it looked like an ingrown hair that he picked at and it got infected (he shaves his chest). I kept telling him go to the doctor. So yesterday he goes and the doctor said that it looked like an ingrown hair but he could have it cut out if it was really buggin him.

So he says I have to get it cut out and asks if I’ll go with him. He said he’s supposed to have a friend with him because of the anesthesia. (All they did was numb the area around the cyst with a needle full of something.) There is a small out patient clinic connected to the hospital right by where we work.

I go with him and the whole thing takes less than half and hour. He comes out all happy. I ask him how he feels, he says “I feel great, let’s get some lunch. I’ll buy.”

So we eat lunch then we’re walking out on to the street (actually a sidewalk), and he say “Mark, what’s a biopsy?” I said “Oh that’s when they test what they cut out of you under to see if you have cancer.”

Then he turns white and says “You mean I have CANCER.” And went right into a dead faint.

I caught him. Well more likely he fell on me. He’s 6’4" and 220 pounds so he wasn’t hurt as much as I was. LOL

Now I have NEVER in my 45 years of living ever seen this before. I have seen people say “Oh I feel dizzy.” I myself have Meniere’s Disease so I know about dizziness. But that is a physical problem.

He was perfectly fine and just the mere thought he might have cancer caused him to go into a dead faint.

He wasn’t out long, not even five minutes. And after I explained the routinely biopsy everything and it doesn’t mean you have cancer, he felt better.

My question is there a purpose to this. I was thinking, is it some sore of defense mechnicism that humans had in the old days and it’s still there. You know how opossums will just play dead. Maybe that dead faint was a response to fear by humans when they were primative, so preditors would think they are dead? I mean I can see fainting if you’re like afraid of flying and you’re very nervous and you get on the airplane get dizzy and faint, but this was real sudden.

Or is is just a fluke kind of thing. You see this thing happen on TV and movies, but I never saw it in real life before

2

First, let’s just say that you might be assuming a function where one doesn’t really exist. It’s like asking what purpose the blue screen of death serves in Windows. Some behaviors/traits are just there. It could be we faint because of some coincidence of other traits. As long as that coincidence doesn’t kill us before we can breed, it’s not going to be removed by natural selection. It could be that removing that coincidence of traits would be more harmful than the fainting.

But being passive is a real survival technique. Possums don’t “play possum” for fun. Many predators have a hunting response triggered by movement and/or flight. Cats will attack a moving piece of string and ignore a stationary piece. As another example, part of the advice in dealing with bears is to stand your ground. Running away is a signal to the bear that you think it can kill and eat you, and the bear isn’t going to disagree with you. :slight_smile:

3

I’m no expert, but as I understand it, fainting is typically due to a common defect in part of the nervous system ( I want to say the parasympathetic system ). It doesn’t regulate blood pressure quite as it’s supposed to, allowing blood to pool away from the head. Instead of, say, reflexively squeezing down on the arteries of the leg to force more blood upwards. So someone with this problem under physical stress ( a disease, standing at attention in the sun ) can lose enough blood pressure in the head that they lose consciousness. This guy was recovering from anesthesia, and then suffered a sudden fright - ever hear of someone going pale with fright ? Blood rushed from his head, and down he went.

4

If I remember correctly (and if I don’t, someone here will):

One of the effects of adrenalin, the ‘fight or flight’ hormone that your body releases under stress, is to open all the little capillaries to give your muscle cells plenty of energy for the ‘flight’ response. This can cause a rapid decrease in blood pressure and inadequate blood supply to the brain, heart, and lungs.

5

While I’m sure that’s possible, I find it really hard to believe: if an individual had gained a trait where, upon facing a life threatening fight-or-flight situation, they faint and lie unconscious for 5 minutes, I can’t see how that trait wouldn’t be selected out by natural selection. It’s just the worst possible response, to the most dangerous type of situation. There must be another explanation?

6

Think of it the other way around; if 1 in 10,000 individuals is prone to fainting during the fight or flight response, but the other 9999 end up outrunning lots of predators and having lots of offspring, the genes for a fight or flight response are going to persist in the population.

Now you’re probably wondering why the high-risk-of-fainting trait (a.k.a. vasovagal syncope in that unfortunate 1/10000 of the population hasn’t been selected out completely. Now IANA physiologist, but there are a few possibilities:

  1. It has a genetic component that isn’t selected against much these days (because humans are social animals who tend to help each other out, and because we have fewer life-or-death encounters).

  2. It has a genetic component, and the genes that contribute to risk factors for vasovagal syncope also have a positive effect that outweighs the negative effect. (I don’t know, maybe they reduce the risk or hypertension or something else that’s not immediately obvious.)

  3. It’s more of a developmental quirk that’s not heritable, but more of an effect of the environment, so fainting people will tend to pop up now and then no matter how deleterious the trait is.

  4. Some combination of the above, or something cool I haven’t thought of.

7

FYI, not all biopsies are to test for cancer. A biopsy is just the taking of a tissue sample for a laboratory test of some kind. For example, biopsies are used in the diagnosis and treatment of Crohn’s disease.

I have read a theory that fainting at the sight of blood may have a survival-related cause. If a person is bleeding badly the body responds by lowering the blood pressure rapidly to slow the blood loss. The sudden drop in blood pressure can cause fainting. In some people this process is over-generalized, so that the blood pressure drops when the person sees blood, regardless of whose blood it is and how much there is.

Fainting from an emotional shock may have a similar cause. Adrenalin causes one’s blood to pool in the center of the body - this can reduce loss of blood in case of injury. It’s possible that this pooling can take enough blood away from the brain to cause loss of consciousness. While it’s true that fainting in the face of danger has a low survival value, protecting the blood supply has a high survival value. Whether blood-pooling is a winning evolutionary “strategy” depends on a lot of things, including how often it causes fainting and how often dangerous situations lead to injuries that could cause major blood loss.

8

Fainting can also be a learned behavior. I wouldnt be surprised if some people are prone to it physiologically but also somehow learned at as a child and have internalized it as a socially acceptable reaction.

*they faint and lie unconscious for 5 minutes, I can’t see how that trait wouldn’t be selected out by natural selection. *

Faiting goats seem to be doing okay. Granted, theyre domesticated, but then again so are humans. Perhaps fainting is fairly new to the species.

9

The aforementioned possums, as well. I think the trick is to mainly have predators that won’t eat carrion.

10

I guess I wasn’t very clear. Your capillaries most definitely do open up, to bring nourishing blood to your muscles.

Should you choose to fight or flee, your exertion will cause blood to return to the heart and lungs; it will not return to your stomach and intestines (I think). I imagine blood must return to the brain, too, but I don’t know the mechanism …

As for fainting (a very odd experience, btw), if your blood suddenly rushes to fill your opened capillaries and you do nothing, there is no stimulus to pump up the heart & lungs, shut down the digestive tract, and a few other things I’ve forgotten …

High fevers are not a particularly beneficial results of the immune system, either.

11

Historically, many people have survived a massacre by playing dead (works best within a heap of actual dead bodies). There are situations where neither fight nor flight is of any use and fainting on the spot may be the best way out. ETA: works at least some of the time with non-predatory animal attacks, too.