[9급 지방직 영어 2013년 20번]

Children usually feel sick in the stomach when traveling in a car, airplane, or train. This is motion sickness. While traveling, different body parts send different signals to the brain. Eyes see things around and they send signals about the direction of movement. The joint sensory receptors and muscles send signals about the movement of the muscles and the position in which the body is. The skin receptors send signals about the parts of the body which are in contact with the ground. The inner ears have a fluid in the semicircular canals. This fluid senses motion and the direction of motion like forward, backward, up or down. When the brain gets timely reports from the various body parts, it finds a relation between the signals and sketches a picture about the body's movement and position at a particular instant. But when the brain isn't able to find a link and isn't able to draw a picture out of the signals, it makes you feel sick.