What typically causes motion sickness?

Motion sickness is primarily caused by a disturbance in the vestibular system, particularly involving the semicircular canals of the inner ear. These canals contain fluid that helps regulate balance and spatial orientation. When a person is in motion, such as during travel in a vehicle, the brain receives conflicting signals from the inner ear, eyes, and deeper body parts. If the fluid in the semicircular canals becomes displaced or the signals are misaligned, it can lead to symptoms of motion sickness, such as dizziness, nausea, and vomiting.

The other options do not directly relate to the physiological mechanisms involved in motion sickness. Disturbances in appetite, gluten intolerance, and excessive food consumption can cause various digestive or gastrointestinal issues, but they are not the underlying causes of the conflicts in sensory information that lead to motion sickness.