Why Does the Endolymph Move Opposite to Head Movement in Vestibular Function?

[sameeralord]

Vestibular function is hard for me. Please help!

Hello everyone,

[PLAIN]http://thalamus.wustl.edu/course/aud9.gif

When you turn your head in the plane of the canal, the inertia of the endolymph causes it to slosh against the cupula, deflecting the hair cells. Now, if you were to keep turning in circles, eventually the fluid would catch up with the canal, and there would be no more pressure on the cupula. If you stopped spinning, the moving fluid would slosh up against a suddenly still cupula, and you would feel as though you were turning in the other direction. This is the explanation for the phenomenon you discovered when you were 5.

First of all I don't understand the pic. Why is the endolymph moving in opposite direction to the movement of head, shouldn't it move the same way. How is inertia involved in this and what is the paragraph saying.

Thanks

 

[torquil]

I think the picture represents a horizontal plane in your head?

By the inertia of the endolymph, it keeps still while the head rotates. Just like a bucket with water. If you suddenly start to rotate the bucket, the water stays still inside. It doesn't start to rotate. But relative to the bucket walls, one can say that the fluid is rotating in the opposite direction. That's what the arrows are supposed to signify in the picture.

When the head rotates, the endolymph fluid and the copula collide, causing a pressure. This pressure is sensed by the brain, talling it that the head is rotating.

I'm no biologist, so there is a fair amount of uncertainty here, to put it mildly...

 

[sameeralord]

I think the picture represents a horizontal plane in your head?

By the inertia of the endolymph, it keeps still while the head rotates. Just like a bucket with water. If you suddenly start to rotate the bucket, the water stays still inside. It doesn't start to rotate. But relative to the bucket walls, one can say that the fluid is rotating in the opposite direction. That's what the arrows are supposed to signify in the picture.

When the head rotates, the endolymph fluid and the copula collide, causing a pressure. This pressure is sensed by the brain, talling it that the head is rotating.

I'm no biologist, so there is a fair amount of uncertainty here, to put it mildly...

Thanks torquil, that was a great answer , much better than the explantion I noted before. I understood everything, how relatively water moves in other direction, but I have simple question since my physics is not good. When you rotate the water bucket, why does water stay still. Is it because you are only rotating the bucket and not the water, so water remains still. If you move it hard though water would also move right. I understood all the rest of the explantion though.

 

[torquil]

Thanks torquil, that was a great answer , much better than the explantion I noted before. I understood everything, how relatively water moves in other direction, but I have simple question since my physics is not good. When you rotate the water bucket, why does water stay still. Is it because you are only rotating the bucket and not the water, so water remains still. If you move it hard though water would also move right. I understood all the rest of the explantion though.

To get things to start rotating, like the water in the bucket, you need to act on it with a force. In the bucket example, not much force will be acted upon the water from the inner wall of the bucket since there is not much friction between it and the water, and the water viscocity is low. The water can slide relative to the inner bucket surface quite effortlessly, so therefore it takes a while of rotating the bucket until the water also rotates significantly, since the force that tries to make the water rotate is small.