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Motion sickness in Wikipedia

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This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Motion sickness". (Source - Retrieved 2006-09-07 14:25:31 from https://en.wikipedia.org/wiki/Motion_sickness)

Introduction

Motion sickness is a condition in which the endolymph (the fluid found in the semicircular canals of the inner ears) becomes 'stirred up', causing confusion between the difference between apparent perceived movement (none or very little), and actual movement. Depending on the cause, it is also referred to as seasickness, carsickness, airsickness, or spacesickness.

Nausea is the most common symptom of motion sickness; in fact, nausea in Greek means seasickness (naus=ship). If the motion causing nausea is not resolved, the sufferer will frequently vomit within twenty minutes. Unlike ordinary sickness, vomiting in motion sickness tends not to relieve the nausea.

Motion sickness on the sea can result from being in the berth of a rolling boat without being able to see the horizon. Sudden jerky movements tend to be worse for provoking motion sickness than slower smooth ones, because they disrupt the fluid balance more. A 'corkscrewing' boat will upset more people than one that is gliding smoothly across the oncoming waves, and cars driving rapidly around winding roads or up and down a series of hills will upset more people than cars that are moving over smooth, straight roads. Looking down into one's lap to consult a map or attempting to read a book while a passenger in a car may also cause motion sickness.

Many 'cures' and preventatives for motion sickness have been proposed at various times. One which is both practical and effective is to simply look out of the window of the moving vehicle and to gaze into the distance towards the horizon in the direction in which you are moving. This helps to re-orient your inner sense of balance by reaffirming to your inner ear that you actually are moving. Fresh air blowing on your face can also be a relief.

Other treatments for motion sickness rely on medication. Over-the-counter and prescription medications are readily available, such as Dramamine. Ginger is a mild anti-emetic and sucking on crystalised ginger or sipping ginger tea can help to relieve the nausea. Interestingly, many pharmacological treatments which are effective for nausea and vomiting in some medical conditions may not be effective for motion sickness. For example, metoclopramide and prochlorperazine, although widely used, are ineffective for motion-sickness prevention and treatment. The sedating anti-histamine medications such as promethazine, work quite well for motion sickness, although they can cause significant drowsiness. Scopolamine is sometimes used in the form of transdermal patches.

Half the astronauts in the U.S. space program have suffered from space sickness, including Senator Jake Garn, who made it his study project while a passenger on the space shuttle in 1985. The specially-designed space shuttle zero-gravity toilet has two settings: one for ordinary waste and another for vomit.

Humans have developed motion sickness as a defence mechanism. The area postrema is a small part of the brain responsible for inducing vomiting when poisons are detected, and for resolving conflicts between vision and balance. When aboard a ship with no windows, one's inner ear transmits to the brain that you are in motion, but the eyes tell the brain that everything is still. The area postrema will always believe the inner ear signal over the eyes, as the eyes are more susceptible to trickery (see optical illusion). Thus, the brain will come to the conclusion that one is hallucinating. It will further postulate that there is a hallucination because of poison ingestion, and so will attempt to rid of the poisons by inducing emesis. Looking to the horizon resolves this conflict, and hence alleviates the nausea.

 

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