Why does your stomach get left behind when an aeroplane drops?

Aeroplanes suddenly drop and you feel weightless. You are almost becoming weightless, normally your stomach is being held up by your body, but if your body is falling at the same rate as your stomach wants to fall under gravity all of a sudden the supporting tissues can relax, pulling your guts upwards.

Your guts and your viscera are quite heavy. They're also hanging inside you so your stomach hangs down below your diaphragm and it's connected to your guts. Everything is pretty much mobile. If you do an operation on a patient it's always amazing to think that when we used to open people up for appendicitis or something you can see the guts writhing around themselves. It's not dramatically fast like a snake pit or something but you can actually see them moving. Everything is mobile, it's gotta be like that to enable things to move. The guts have to be able to stretch to take in things and shrink again when things move through them. Because it's all not fixed inside you if you go over a bump when the car or aeroplane drops on the other side of the bump your body is a bit left behind for a little while. There's enormous number of stretch receptors and vibrations sensors in your guts. That's why people talk about having a gut feeling for something. It's very true. A lot of the frequencies that we get from the world around us, the low frequency vibrations are felt in your abdomen and you think you're sensing them from your abdomen but enormous amounts of that information comes from your gut. It's a gut feeling, quite literally. Because those stretch receptors get excited when your guts literally fly up in the air with your body moving down around them. As a result it does feel like you have a sort of sinking feeling. The other reason you get a sinking feeling is because you might get a bit frightened. When an aeroplane suddenly drops you can have that moment of terror, 'Oh my god, is the aeroplane gonna drop out of the sky?' What happens then is you get a little surge of adrenaline. Your sympathetic nerve system kicks-in in a very big way. That's the part of the nerve system that gears you up if you're going to run away or have a big fight with someone. That produces lots of adrenaline and adrenaline powerfully switches off your guts because the one thing you don't want to be doing when you're trying to run away is wasting your blood supply feeding your guts. You want your blood going to your muscles and your lungs every other part of your body when you need to run away of fight. So you turn off your guts and that turn-ff signal gives you that sinking feeling or the butterflies you get in your stomach so it could be possible a combination of the two effects, I reckon.