Syncope. Great word. SIN-co-pee. (I prefer SINK-oh-pee.)
Summertime, during college, I worked on a construction crew. One job was in the woods, following behind a D-9 CAT as it pushed down trees, clearing a path for a sewer line (the job I then had building manholes killed the guy that took over for me when I returned to college. That's another story). I'd saw 'em up with a chainsaw, buck 'em up with an axe. Filling the wait time, I kept that double-bladed axe sharp as a scalpel, honing it with a broad file, the metallic hrrizzzzzz, hrrizzzzzz and the sway of my hardening shoulders convincing me I was Paul Bunyan. In one of my moments of brain-body disconnect (I also nearly produced a sagittal section of my head with the chainsaw, cutting a log lying across a gully, above me), I tried whittling with that axe, whizzing it past the fist that held my would-be chunk of wood sculpture. Gee, I thought. I could really hurt myself; and with that, I did it again, this time slicing into me just beyond the sino-thumbic M-P joint. It bled quite a lot.
After a few comical moments, wherein I grabbed my thumb and flagged down the CAT driver, who hopped off with a first aid kit and tried dabbing an iodine ampulet into the considerable flow, I found myself in the office of a nearby doc. "Lucky you didn't get the tendon," he said. And then, "Oh, it looks like you did..." As he readied his suturing materials, he suggested I lie down. "Naw, " I blustered. "I'm gonna go to med school. I've dissected frogs. This stuff doesn't bother me." So I watched as he injected some local and began sewing. It wasn't the blood, or the hurt. It was the sensation of feeling some sort of tug as the needle passed: I thought I could hear it or something. An awl through leather. Weird. About the time he looked at me and suggested again that I lie down, I said I thought I might go ahead and lie down...
I've seen a lot of people faint over the years. Since an episode during internship when a friend of a patient who'd insisted on watching as I sewed him up fell like a log, straight and unfettered, to a concrete head-lacerating floor, I've anticipated it. Still, it happens. Nearly always, on arousal, the fainter is embarrassed. Don't be, I'd tell them. It's natural. There are some situations when it's best to lie down, and when we fail to recognize them, or act, our brains are wired to see to it that we do. I always liked that explanation. I think it might even be true.
It's interesting. For some threats to our well-being, our adrenals squeeze like a fist and out comes the "fight or flight" response. Pumped up, ready to go. (Or is that "fired up...") For other situations, the better choice is "sit down and shut up." When you think about it, it makes sense. For a threat before which you remain more or less intact, a racing heart and fleet feet seem right. If, however, things take a turn such that your pipes are open with fluids leaking out, it might be wise to shut things down. So I think fainting is nature's way of telling you to cool it. If you're too dumb to get your brain at or below heart level, your head will make the move for you. And turn down the pump at no extra charge.
Well, nothing's perfect. Why we should keel over when someone else is in trouble escapes ready explanation, at least by me. Maybe it's slop-over, an individually exaggerated form of communally-needed empathy. You know you should help, you want to help, but shit-oh-dear: gotta take a pass! Of course, it might ensure that you'll have a second chance when you both wake up.