Please do this:
- Go to a mirror.
- Stare straight ahead.
- Find a marking/discoloration on your iris or some distinguishing vein that you can watch during this process.
- Rotate your head to the left and then the right taking notice of the compensatory motions of your eyes.
What do you see?
- Now try it fast.
- See how far your eyes will rotate.
Think about it. Your eye gyroscopes all the time and you've probably never really thought about how (or, at least, I didn't).
Here's the gist of what I understand to be happening. Your inner ear is composed of channels filled with liquid that as we move cause slight currents to be detected by the minute hairs within the vestibule.
That information then follows the below path:
It then tells muscles wrapped around the eye to rotate the eye:
Notice the way the muscles wrap around the eye making it possible to rotate the eye.
The exceptions to this rule are worthy of note. Ever felt like the room was spinning? Maybe that's because your eyes were!! When you drink, spin yourself, or put cold/warm water in your ear the brain receives some confusing signals that end up causing the vestibulo-ocular reflex to get a little wonky (called nystagmus). Your eyes rotate when they shouldn't!! Also, when a doctor is trying to to assess the severity of a brain injury and possibly determine if the patient is brain dead, rotating the head to see if the eyes rotate involuntarily is one method.
Not even going to pretend I didn't steal this from Wikipedia:
"Using these direct connections, eye movements lag the head movements by less than 10 ms, and thus the vestibulo-ocular reflex is one of the fastest reflexes in the human body." http://en.wikipedia.org/wiki/Vestibulo-ocular_reflex