Motion sickness

Your brain gets information from several sources concerning the type and direction of your movements. The first, and most important, source is the inner ear. The inner ear, also responsible for balance, contains fluid that shifts according to your body's movement, pushing little hairs one way or the other. This lets your brain know about the direction you're moving in. Your brain also receives information from the eyes, skin pressure receptors that tell the brain what parts of the body are on the ground, and muscle and joint receptors that tell the brain which parts of the body are moving. The central nervous system (the brain and the spinal cord) compiles all of this information to create a complete picture of what is happening.