Motion Sickness (e.g., Seasickness, Carsickness) -- Physiology
The brain relies on information from multiple body systems to balance itself and establish equilibrium. When the body receives conflicting information from these systems, the brain struggles to make sense of it. The result is that some people feel nauseated and dizzy.
Spatial Orientation:
Many systems help the brain establish where the body is and what it is doing. The sense of sight and touch, the balance components of the inner ear, and muscle and joint receptors in the body all send messages to the brain regarding the body's activity. These systems help reveal the body's:
- location -- where the body is located in relation to other objects and the ground
- movement -- whether the body is stationary or moving, what direction it is moving, and how quickly or slowly it is moving
- position/activity -- which body parts are supporting the body's weight and what the body parts are doing
The brain then interprets all of this input and, along with the spinal cord, controls the body accordingly. However, sometimes the messages the body sends to the brain may be in conflict with one another.
For example, the inner ears and the eyes may send different signals regarding whether the body is moving or not, such as when a person on a cruise ship is sitting quietly in a cabin below deck. The eyes tell the brain that the body is sitting quietly in a room and not moving, while the inner ear -- feeling the body move with the gentle rolls of the ship -- tells the brain that the body is moving. The brain then struggles to make sense of this conflicting information. When this confusion occurs, symptoms of motion sickness can result.
