Disclaimer: this thread isn't meant to be morbid. With luck it will be a long time before what I'm about to describe happens to anyone reading this... But death is inherently a part of life, and nobody is promised tomorrow. Rather than a silly fear of your own mortality, considering this topic is intended to give you a sense of wonder at the complexity, sophistication, and glory of your own self. Well, that and it's giving me a break to distract myself from the fact that I've sacrificed the entire weekend to study this shit and I'm still working while the rest of you are passed out drunk. Fuck you all.There's something alive inside of you. It needs you, and you need it: it gives you life, and you feed it... but
your heart has a life of its own. It can survive without you, at least for a little while. As a youngster you might have heard about the Aztecs, who would sacrifice prisoners of war in a sacred ritual:
The climax of this ritual was evisceration of the living prisoner to remove their heart whole, which was placed,
still beating on an altar. See, your heart doesn't need you around that much to keep doing its thing.
Unlike your lungs, which need that pesky brain of yours around to keep bringing in precious oxygen, the heart beats all by itself. It has its own
pacemaker! You've probably heard the word used as something that people get installed when their hearts are messing up, but normally the heart gets its own rhythm in a place called the
SA node. The SA node sends pulses of electricity through your heart at regular intervals (usually between 80 and 120BPM), every minute of every day,
day after day for your whole life! Your brain has some say in the process: it can speed things up if you're exercising, but that's pretty much it. As long as you feed it occasionally and get it enough oxygen, things are fine: you don't fuck with your heart, and your heart doesn't fuck with you.
Your heart's system of pacemakers is very, very well designed to keep going even if something breaks. If the SA node pacemaker suddenly stops working, other electrical pacemakers take over almost immediately. As long as your heart is getting signals from a single dominant pacemaker, everything is fine.
See, there's one main thing that you need for your heart to work well: it has to beat. Think of the pacemaker as the DJ and the heart's muscle as dancers: It can beat fast or slow, it can seamlessly switch tempos or it can jump back and forth like an ipod DJ, but as long as there's only one kick drum everyone can feel the rhythm; the heart still does its job well enough to keep you alive. When this is normal, each beat (lub-dub) has an electrical signal that looks like this:
See? Nice and regular. You could clap in time with this.. in fact, most music is in the same range of tempos as your heart!
So there your heart is, pumping away like it has for decades. Then something happens, something bad: that good for nothing body is sick or injured, and it can't get enough oxygen.
This makes the heart unhappy. Very, very unhappy. Some of the cells that shouldn't be pacemakers try and jump into the mix, playing their own rhythm-- but they can't beatmatch for shit, and the result is a nasty trainwreck. Just like in real life, the dancers stop moving in sync: they can hear more than one rhythm, and they can't follow both!
This looks just as chaotic as it sounds:
or
See? No rhythm whatsoever... and guess what, no pumping either. This is called
fibrillation and it's
very very bad. The party's not over yet-- the dancers are still there, even though they're pissed-- and you're not quite dead yet. If you see someone in a hospital show reaching for paddles and yelling "clear" before shocking the shit out of someone, this is why. That's called
defibrillation: by sending a strong shock through the heart, you shut down all the competing signals and give the real DJ a chance to reassert control. If he does, normal rhythm comes back and the dancers move in sync once more -- your heart pumps again.
What if it doesn't work, or if nobody is standing around with an AED to shock your ass? Well, the heart isn't getting any blood either, and eventually it becomes so weak they can't pump anymore. Party over.
So long.
You could choke on a falafel, get your head chopped off by unruly frenchmen, or have your heart torn out by enthusiastic mesoamericans, but your heart's story almost always ends the same way: not enough oxygen, wack wannabes bring one final trainwreck, and the dancefloor clears.
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