Losing your stomach

[dk_psy]

What is that sensation when you 'lose your stomach' when on a rollercoaster or going over a bridge or hill quickly in a car? I know it's negative g-forces causing the sensation, but what actually happens in the body to cause the feeling?

[fo3nix]

i would have thought it would be the stuff in your stomach rising and falling.

only a guess though.

[MargeB]

Just torso proprioception, really. You have a 'sixth sense' of where your 'body' is, and this is disrupted, especially for your organs.

[stevie21]

It's not a sixth sense at all, just a sense.
Do we really need to introduce something mysical to explain something perfectly sensible?

Like a dog's, your belly and insides just hang there. In our case they all sit on top of the gumph above our pelvis as opposed to hanging down below our ribs (dogs). They're not really held in place too tightly by anything.
When we go over a bump, they are thrown up in the air a wee dod like anything unattached.

Each part of our body passes info back to the brain about where in space it is so if we hold our arm aloft then even if we don't remember (or see) it being lifted then we can *sense* that it's lifted. Our organs can also give info about their relative position.

[Clanad]

Actually, motion sickness has little to do with one's stomach, except that it is affected by the disconnect between the sensations of movement sensed by the body, the eyes and the circular canal of the inner ear.  All three send signals to the brain to let it know what's going on and "where" one is.... it's place in space, so to speak. The next time a child or adult, for that matter, spins around for a while, as in an office chair or the twirling children do, stop them suddenly and look at their eyes.  They are making small, rythmic jerking motions.  The circular canal is telling the brain it's still moving, because the fluid in the canal hasn't stopped, and the brain is trying to verify that since the body is telling it that it's stopped.  The eyes are trying to help determine what is actually going on.  All of this produces nausea, cold sweating and a general feeling of discomfort.  These feelings are aggravated by more violent motions, such as roller coasters or turbulence in aircraft...

[MargeB]

lol, I love it when you interject, stevie21, while not actually knowing what you're talking about. It is a seperate sense, not an extension of touch. There are quite a few people who have touch intact but who lack this sixth sense and who fall into a crumpled heap without visual cues as to their bodily position.

No offence, but a quick pointer for using Answerbank,  since you seem to be doing this all the time- instead of just trying to trample over people's posts with your own guesswork, try to inform yourself, even just a little, and then post. It'll stop us all getting bored with your 'offerings'.

[MargeB]

The vestibular system that Clanad mentions and how it can become confused with the proprioceptor system is detailed in the 'Mixed up in Space' link within this article which details the sixth sense I was talking about:

http://serendip.brynmawr.edu/bb/neuro/neuro02/web2/slee.html

[dk_psy]

woah, didn't mean to start an argument! Thanks very much for such a quick response everyone! This is a wicked site and I only really signed up to ask that question, but think I'll find myself more of a regular visiter now (though I'm sure I'll be able to help on very few questions!).

 

t.

[MargeB]

You're very welcome dk, it's an amazing site.

[MargeB]

So Clanad, as I'm seeing it, when you fly over a hill fast in your car, your vestibular system thinks you're in trajectory, but your proprioceptive doesn't?

[stevie21]

Marge, before I bow to your superior knowledge, could you tell me this...
"There are quite a few people who have touch intact but who lack this sixth sense"

Is this possibly akin to saying "speech is completely separate from being able to pronounce the letter R. Jonathan Woss can do one but not the other" ?
Could it be that it's part of the touch sense, part that works in most but not in others?
Also, as unlikely as this is, would it then be possible to have this sixth "where in space" sense intact but have no other sense of touch?

[Clanad]

Well, MargeB, proprioceptively speaking, it works for me...

[stevie21]

Marge, any chance that you could answer the questions put to you here?
e.g. Is it possible that this is *part* of the sense of touch?

[Peter Pedant]

I have to say i thought it was obvious.

The body organs hang in there and stretch the peritoneum and this gives an idea - but only an idea [marges sixth sense i thought oK and not mystical at all] of where they are.

When you go in a dive there is an acceleration (in the opposite direction)and therefore a force upwards and the peritoneum is not tweaked as much as before giving the sensation.

All this comes from the cat righting reflex research in the seventies. Researcher holds kitty paws up and lets go, and the kitty rights the head using visual cues and vestibular cues and then rights the body, using der daaah cues from the peritoneum.

Read a modern edition of ganong's phys - most of the ABers seem to have.