Symptoms of Seasickness
Confusion, dizziness, loss of appetite, nausea, and vomiting are symptoms of seasickness. The onset of these symptoms is usually abrupt, and the symptoms increase in intensity with higher seas. They cease when the victim has become accustomed to the motion or when calm water or land is reached.
Causes of Seasickness
Seasickness is believed to result from a combination of kinesthetic, visual, and psychological factors. Kinesthetic disturbances affect the semicircular canals of the inner ear, which are the chief controls of body balance. When balance is lost on steady ground, nerve impulses from the limbs reach the inner ear and are transmitted to the brain. The brain integrates the impulses and transmits corrective impulses back to the limbs to right the body. However, during the accelerating and decelerating motions of the deck of a ship, haphazard impulses from the limbs become difficult to integrate and the sense of balance is disrupted.
Visual factors may increase the incidence and severity of seasickness symptoms. On land, the horizon is fixed at one level and serves as orientation in space. When the horizon is viewed from a moving vessel at sea, however, it may appear to rise, shift, or tilt too fast or too inconsistently for the visual sense to follow.
The psychological factor is believed to be a paramount cause of seasickness. Some or all of the symptoms may result from anxiety at the loss of secure, steady body support.
Drugs such as antihistamines, parasympathetic depressants, and sedatives are often successful in preventing attacks of seasickness if taken beforehand.