BAM! You’re On The Floor!

(Well, I could do without the obnoxious laugh track. Things like this were so much funnier to me before I started with the whole medical training thing. Now all I can think about is how much their medical bills are going to be.)

(Anyway. Article.)

We see fainting everywhere in fiction, from swooning damsels in distress to buffoons scraping for cheap laughs in mindless comedies. And heroes are always fighting off a loss of consciousness when they’re being tortured by evil bad dudes everywhere, and annoying sidekicks are always dropping into the nearest pile of horse puckey at the sight of blood.

So what’s going on? Is there a medical explanation?

Of course! 😀

If your brain doesn’t get enough blood flow, it’ll shut down. And this causes a person to lose consciousness. That’s called syncope. If they’re upright, they’ll fall down. (If they don’t lose consciousness, but still experience dizziness and other near-syncope-like symptoms, it’s called….near-syncope. Thought it was going to be more dramatic, didn’t you? 😀 ) True syncope is also characterized by a relatively quick recovery, with no real neurological after-effects.

So, listen. Gravity is always pulling your blood down toward the center of the earth. Your cardiovascular system is all set up to fight against this force to keep the blood circulating adequately to all parts of your body, no matter what orientation it’s in. It’s a rockin’ system.

But if something goes wrong with the cardiovascular compensation against gravity, gravity wins. And the blood gets pulled away from whatever is the highest part of the body. If it’s your brain, your brain will shut down until enough blood gets back into it.

As a side note: fainting sure isn’t fun, but it’s a pretty smart failsafe in case gravity starts winning. It gets you horizontal, on the ground, so your brain is a low enough point that gravity won’t pull too much blood away from it. Cool, huh?

So what causes the failure in the first place?

There are a lot of reasons why people faint. As a matter of fact, I dreaded getting a syncope case during my time-limited practical exam for my boards, because there was SO MUCH WORKUP to do that I’d never get to everything in time. The ultimate cause could be in the heart, or the brain, or the lungs, or an imbalance in the blood…..and it could be any number of causes within those categories. Like I said, lots of reasons.

But how about fainting in fiction? The guy who passes out instead of revealing the secret location of his hidden army while under duress? The girl who can’t stand the sight of needles? The dude that gets overrun by carnivorous spiders because his maladaptive phobia causes him to faint when he should be running away, and thus provides an opportunity for us to see exactly what said carnivorous spiders would do to our erstwhile hero if they could manage to outsmart her? The poor folks in the wedding videos?

It’s probably all from the same end cause: vasovagal syncope.

Say what now?

Vasovagal (vaso – blood vessels, vagal – having to do with the vagal nerve and parasympathetic function) syncope (fainting).

This can happen with a strong emotional shock, or with a large, sudden amount of pain.

Here’s what happens. The sympathetic and parasympathetic influences are in their tug-of-war balance, keeping heart rate, blood pressure, breathing rate, etc. all around their preferred normal baseline ranges. Suddenly, there’s pain or terror, or something that strongly stimulates the sympathetic branch of the nervous system (the fight-or-flight branch)! The sympathetic tone leaps WAY out of balance, and the tug-of-war leans STRONGLY to the fight-or-flight side.

In reaction to the increased sympathetic tone, the heart contracts HARD! (Remember, in a fight-or-flight situation, it’s a good idea to have more blood pumping through your system.)

Then, sensors in the heart that are supposed to be keeping an eye on the balance between the sympathetic and parasympathetic tone see that the sympathetic tone has completely overwhelmed the parasympathetic tone! And they freak out! They have to balance the discrepancy somehow! So they send signals to increase the parasympathetic (“vagal”) tone!

But then, the overwhelming sympathetic tone reduces to a certain extent, because it was probably a bit of an over-reaction.

Now, all you’re left with is an overwhelming parasympathetic influence, which drags things STRONGLY over to the rest-and-digest side! This means heart rate, blood pressure, etc. all drop like stones. And if your blood pressure drops enough that it can’t pump enough blood to your brain, BAM! Your brain shuts down and you’re on the floor.

Illustrate that point with a random side story!

How funny that you’d encourage me to do such a thing. It’s almost as if we were both internet-based entities being written by a single author for the purpose of increasing the accessibility of a blog post!

I’ve actually experienced vasovagal syncope. Pretty recently, as a matter of fact. In my hapkido class, I was teaching a lower belt how to do a particular combination of a joint lock and throw. And she did it really well. So well, in fact, that she threw me right off the mat. I hit my knee really hard on the floor, and it hurt like crazy.

And then, not realizing that I had just experienced a potentially triggering stimulus, I got up off the floor to show her how to position herself so she didn’t throw me off the mat the next time.

And I started feeling nauseous. And dizzy. And woozy. And a little hot. And what do you know? I actually recognized the symptoms! I felt my pulse, and sure enough, it was much slower than it should have been under the circumstances. And I remember thinking, “If I don’t lie down on the floor RIGHT NOW, I’m going to fall down on the floor.” So I lay down. Just in time.

Every time I tried to sit up, I felt the same faintness. So I stayed down until my body figured out that I was actually okay, and my autonomic nervous system sorted itself back out into its proper balance.

Okay, but this whole explanation doesn’t exactly follow for the wedding videos. I mean, the brides weren’t THAT hideous. Neither were the grooms, for that matter.

Well, there’s something else that causes a vasovagal response.



If there’s nothing going on that activates your sympathetic system, your autonomic nervous system gets so bored that the sympathetics just shut down. Your heart rate falls. Your blood pressure falls. You lose tone in your blood vessels, and they dilate to their full extent. Blood falls down through your legs and away from your brain. And bam! You’re on the floor!

This happens to medical students all the time. (A medical student’s job during a surgery is usually to stand and watch. And hold the retractors that pull tissue away from where the surgeon is working. For. Hours. On. End.) One of the first things they told me during my surgery rotation was what to do if I started feeling faint. Because situations like that are very, VERY risky for the whole vasovagal syncope thing.

It also happened to my little brother a lot when we were singing in choir performances under hot lights, doing weird musical-but-non-physiological things with our breathing. It happens to people who are standing in crowds listening to politicians talk. It happens to people standing during a wedding ceremony.

But this all hinges on gravity, right? What about astronauts?

Okay, I gotta drop this in here. I actually don’t know too much about what happens in an actual zero G environment. I can guess. But, I think it’s even more interesting what happens after they get back to Earth.

After a while in zero G, astronauts’ bodies tend to forget their antigravity compensation mechanisms, because the body hasn’t used them for a while. So when they get back into a gravitational environment, they experience orthostatic hypotension for a while until the compensatory mechanisms remember how to kick back in.

Oh, how I loves me some physiology! (Does it show?)

(Anyone else wanna clock that guy at the end, or is it just me?)


Ganong, William F. Review of Medical Physiology. 21st edition. McGraw-Hill, 2003.

McDermott, Daniel, et al. Approach to the adult patient with syncope in the emergency department. UpToDate, May 2010.

Sabatine, Marc S. Pocket Medicine, 3rd edition. Lippincott Williams & Wilkins, 2008

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Published in: on August 26, 2010 at 10:47 am  Comments (22)  
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22 CommentsLeave a comment

  1. Great post, Doc, and much appreciated!

    When I first arrived in boot camp, the guy in the top bunk over me was newly arrived from high-altitude Colorado. (We were in Orlando.) For the first 4-5 days of boot camp, he would jump out of bed at reveille, stand on the line with all of us to watch the drill instructor’s morning antics… and faint dead away within 3 minutes of getting out of bed.

    It was all fun and games till he went face first into the rifle rack. 🙂 We had to have smelling salts on hand for him 24/7 till he got used to the O2 level or something like that.

    Speaking of. Bonus question: Why/how do smelling salts work? (or do they?)

    • Aren’t smelling salts made of ammonia or something? Some really noxious odor? Strong olfactory stimulus ==> jolting out of unconsciousness?

      I’d have to look into the mechanism.

  2. I’ve experienced/seen this in rugby. Occassionally, after a big hit with no head contact or “whiplash”, you jump up to follow the play and fall over like you were staggering drunk. You lay down just long enough for the trainers to worry that you are concussed and are fine with no concussion symptoms. I clearly recall an instance where I thought, “Why did my foot miss the ground?” as I “got horizontal”.

    That being said, rugby is a contact sport. So you still want to get checked for those concussion symptoms.

  3. Ah, unconsciousness! There is so much you can do with it (as that guy at the end of the video found out… sorry.) Knock the bad guy unconscious and run away. Hero gets knocked unconscious, and the bad guy can do anything to him/her.

    It’s great to know more about what causes it. I can use that… Thanks!

    • I need to point out: This is only ONE of the reasons people go unconscious. There are many, many ways. This particular mechanism is only appropriate for strong painful/emotional stimuli, or standing for hours doing nothing.

      • Oh, heavens yes. My favourite reason for unconsciousness is shock — my poor characters must hate me terribly!

        Head injuries come in a close second.

        Yes. I’m mean to my characters. I’m always looking for new, interesting ways to get them in trouble… 😉

        • One of my friends took me out to see “Stranger Than Fiction” when it was in the theater, to obliquely plead for the life of one of my favorite characters.

          And then he not-so-obliquely pleaded for her life.

          In vain.

          (I feel the urge to say: bwa-ha-ha-ha-ha.)

          I’m not kind to my characters either.

  4. those images really helped, I recognized myself falling…
    Reading the page really helped too, since the last thing I heard about my fainting’s cause was that it probably was psycho-somatic, straight to the Divan as my friend Hélène said, whom I want to thank for having shared this blog with me.

    • Welcome, Anna! Nice to have you around!

      Some fainting IS actually psychosomatic, so whoever told you that may not have been entirely wrong. In the biz, it’s called “psychogenic syncope”. It isn’t always purposeful, either; it can be something your mind does without conscious intent. Because our brains are weird. 😀

  5. Fantastic post, per usual. 🙂

    I have a friend who always passes out when she gets blood drawn, so much so that it’s a running joke for her. (I don’t faint, so instead I focus on not making pathetic whimpers so as not to annoy the tech.)

  6. I’m a champion fainter, so I thought I’d add some info just for fun.

    I have fainted while getting blood drawn.
    I have fainted because of cutting myself while cooking.
    I have fainted while walking down the street.
    I have fainted while ill.
    I have fainted while perfectly healthy.
    I have fainted at concerts.
    I have fainted in school.
    I have fainted at work.

    Usually but not always, it’s because I see blood. I don’t have to experience pain for it to happen. I usually feel nauseous, then dizzy, then BAM. The thing I find most curious about this is that always always always when this happens I hear a train and a very specific song in my head. It plays until I come to, and then it slowly fades away as I start to understand what people are saying again.

    And I should probably add that I don’t have any disorder that makes me faint a lot. It has happened maybe twenty times in thirty years, and usually at the least convenient of times.

    My sister tells me I swoon like a maiden fair in an 18th century novel. She has a point, I have to say.

    • It’s incredibly common to have that kind of reaction to blood. It falls under the category of “strong emotional response”; people don’t like seeing their blood outside of their body.

      Only doctors and serial killers want to see blood outside of a person’s body.

      You know, and mosquitos.

      And vampires, I guess.

      Anyway, the point remains valid.

      I think.


  7. […] BAM! You're On The Floor! « How To Kill Your Imaginary Friends […]

  8. I have never, ever fainted, and I kind of resent it. I’ve had nasty shocks, I’ve been in terrible pain, I’ve been sick almost to death, and I’ve had to be conscious through it all. Hell, I woke up halfway through a surgery once — just enough that I could feel it.

    So my characters don’t get to pass out, either. I think it adds sadism realism.

    Can you cover “hit on the head and knocked unconscious” sometime? 😀

    • Sure! I’ll need to do some research, though. Maybe during my neuro month.

  9. So if I want to create a world with a different gravity from earth’s, my characters should probably have a different cardiovascular system too? Or at least a cardiovascular system set up to combat the gravity on their home world.

    And then, if I move them between worlds, interesting things should happen…

  10. hmmmm.
    nice video.we can sleep anywhere….or fall.

    • You better hope you can fall! Otherwise, you might suffer brain damage before the autonomic system gets its rear back in gear!

  11. With all of those grooms fainting one has to wonder if, on a subconscious level, they weren’t all looking for a way out! 😉

    • Assuming they went the traditional route, if they didn’t want to get married, they shouldn’t have asked…. 😛

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