Motion sickness

Motion sickness is caused principally by conflicting sensory information. The motion usually has a rhythmic or erratic character. The inner ear monitors direction of motion. The eyes monitor where the body is in space (upside down, for example) and sense of balance or equilibrium. Skin pressure receptors, such as on the feet, tell the brain which part of the body is in touch with the ground. Muscle and joint sensory receptors tell which part of the body is moving. The central nervous system processes information from the four systems. Motion sickness is caused when the brain receives conflicting stimuli.