Re: When spinning around, if you stop and spin the other way does it help

Hi-

     That's a good question! The basic answer is that it would indeed help a little bit - it would help things get back to normal faster than if you stood still. But you still might be a little dizzy at first when you're trying to spin the other way.

     To understand what's really going on, we need to know some nitty gritty details. The vestibular system is what your body uses to figure out if you are lying down, standing up, leaning to the side, spinning, etc. It is comprised of the semicircular canals, the utricle, and the saccule. When you're spinning, you're feeling your semicircular canals at work. I'll try to give a bit of detail here. (More in depth info can be found at http://thalamus.wustl. edu/course/ audvest.html, under part E: the semicircular canals.)

     Inside your ear, the semicircular canals are filled with fluid; they detect rotation of your head in space (like when you shake your head side to side, or when you're in a car that's turning). There are three canals in each ear, detecting 3 dimensions of motion. Roughly speaking, these dimensions of movement are shaking your head (as if to say 'no'), touching your ear to your shoulder, and touching your chin to your chest.

     Inside these canals, fluid flows around the canals and can slosh against the cupula. The cupula is a gelatinous goop which is attached to hair cells, the cells which send the 'balance' signal to your brain. When you move your head, the fluid can't react as fast as your head does. The fluid pushes against the cupula, which causes the hair cells to move.
     It's somewhat like you putting an oar into the water of a river you were canoeing down - the moving water (fluid) would push your oar (the cupula) back. The hair cells would be like your arm - you'd detect that oar was being pushed back!

     So, as we said, when you start spinning, the cupula gets pushed on by the fluid. But if you were to keep on spinning at the same speed for a little bit, the fluid would catch up with your head, and would be spinning at the same rate as the rest of you - and you would stop feeling dizzy. But once you stopped, the fluid would want to keep flowing at the speed you were spinning, and slosh up against your cupula again - making you dizzy again!

     If you start spinning the other way, you would be exerting another force trying to push the fluid into the new direction of motion. This means you would be pushing on your cupula even more than if you just stopped. But that would be short lived, as the fluid would eventually succumb to the force from the other direction, bring it to stop more quickly. (and if you keep on spinning you'll get it going in the new direction).

     I hope that makes sense. In summary, the fluid in your ears still sloshing around causes you to feel dizzy when you stop spinning in one direction. If you turn the other way, you will drive that fluid to start spinning the other way. This will cause the fluid to come to a stop sooner than if you just tried to stand still (but not immediately)!

-Alex G
cgoddard@fas.harvard.edu