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Both inner ears monitor the directions of motion in three dimensions.
Our eyes observe where our body is in relation to its surroundings as
well as the direction of motion. Skin pressure receptors such as those
located in the feet and seat sense in what direction the gravitational
pull affects our body, in other words: what side is up? Muscle and joint
sensory neural receptors report which parts of the body are in motion
and in which relative direction. All these sensory data will
subsequently be processed in the central nervous system, which enables
us to balance, move and position ourselves properly in our three
dimensional surroundings.
Symptoms
The symptoms of motion sickness appear when the brain
receives conflicting messages from the 4 systems. And a conflict on
board can easily occur : when reading a book on deck your eyes observe
no motion, yet your inner ears feel the motion of the yacht due to the
waves. The first telltales of such a conflict are often lethargy and a
slight drowsiness. But for the victims it will usually start with a
nauseous feeling and/or a slight cold sweat. Then these symptoms
increase, and the face becomes paler, perhaps even greenish. Any attempt
to concentrate on a task will worsen this predicament. The nauseous
feeling eventually becomes incontrollable, and leads to - sometimes
violent - vomiting.
Prevention
Hours before casting off you could well use an over-the-counter
antihistamine such as meclizine or dimenhydrinate and you should -
before and during the voyage - avoid spicy or rich foods, alcohol and
apples. For longer trips, a prescription medication called Transderm-Scopolamine
patch can be worn behind the ear for up to three days at a time.
Side-effects of these medications usually consist of sedation and dry
mouth. Interestingly enough, recent studies have shown that ginger root
may be as effective as the other drug treatments but is associated with
fewer side effects.
If, despite all these precautions, you still notice the early
symptoms with one of you crew, act immediately and get the victim out on
deck but not in direct sunlight. Don't give the victim any task other
than steering. Steering - as well as studying the horizon works and will
help to anticipate the boat's motion. Steady the yacht, either by
heaving to or letting the best helmsman drive the yacht.
The Gundogan usually has medicines onboard to counteract sea
sickness.
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