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What is motion sickness?
Motion sickness is a condition with symptoms like dizziness, nausea, and vomiting, that arises from being exposed to unnatural motion. It occurs when the inner ear's balance center sends movement signals that contradict the signals the eyes send. For example, inside a ship cabin, the inner ear detects the ship's motion, but the eyes see a stable environment. Avoiding the motion is key to preventing motion sickness. If that's not possible, fixing the head, focusing on distant objects, or closing the eyes may help. Medications like antihistamines can also provide relief, though they may have side effects.
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What causes people to experience motion sickness?
Motion sickness arises from conflicting signals sent to the brain by the eyes and the balance center in the inner ear during movements like swinging or rocking. The inner ear's vestibular system detects changes in body position, while the eyes register stability by observing external surroundings.
When these signals contradict each other, as in seasickness where the inner ear senses motion but the eyes see a stable cabin, the brain becomes confused. This confusion triggers the release of stress hormones and disrupts stomach muscle rhythms, leading to symptoms like dizziness, nausea, and vomiting.
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What are common symptoms of motion sickness?
Motion sickness results from exposure to unnatural accelerations, triggering symptoms like dizziness, pallor, cold sweats, increased salivation, nausea, and vomiting. This condition arises from conflicting signals sent to the brain by the eyes and the balance center in the inner ear during movements like swinging or rocking. The inner ear's vestibular system detects changes in body position, while the eyes register a relatively stable scene, causing confusion in the brain.
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Why do some people get motion sickness more easily than others?
Motion sickness arises from conflicting signals sent to the brain by the eyes and the balance center in the inner ear during movements like swinging or rocking. The inner ear's vestibular system detects changes in body position, while the eyes perceive stability based on external surroundings. When these signals contradict, as in seasickness where the inner ear senses motion but the eyes see a stable cabin, the brain becomes confused. This confusion triggers the release of hormones like epinephrine and norepinephrine and increases stomach muscle electrical activity, leading to nausea and vomiting.
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How can motion sickness be prevented or reduced?
Motion sickness can be prevented or reduced through several strategies. The most effective measure is to keep the body, especially the head, still in relation to the vehicle.
To minimize accelerations, consider seat location, time of day, and vehicle type. Other helpful tactics include sitting in a reclining position, avoiding head movements, closing your eyes, and focusing on distant objects. Concentrating on other tasks may also help.
Several drugs can prevent or relieve motion sickness, but they often have unwanted side effects. Effective drugs include scopolamine and promethazine. Antihistamines like diphenidol, dimenhydrinate, cyclizine, and meclizine can also decrease susceptibility.
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What are some treatments or remedies for motion sickness?
To treat or prevent motion sickness, focus on minimizing motion, especially of the head, by fixing the body in relation to the vehicle. Strategies include choosing vehicle and seat location, reclining, avoiding head movements, closing eyes, or focusing on distant objects. Reading, eating, drinking, anxiety, and stress can worsen symptoms.
Several drugs can help prevent or relieve motion sickness, though they often have side effects. Effective options include scopolamine, promethazine, antihistamines (such as diphenidol, dimenhydrinate, cyclizine, and meclizine), anticholinergic drugs, and serotonin antagonists like ondansetron.
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motion sickness, sickness induced by motion and characterized by nausea. The term motion sickness was proposed by J.A. Irwin in 1881 to provide a general designation for such similar syndromes as seasickness, train sickness, car sickness, and airsickness. The term, though imprecise for scientific purposes, has gained wide acceptance.
Symptoms of motion sickness
Motion sickness comprises a constellation of symptoms resulting from sudden exposure to periodic unnatural accelerations. The symptoms include dizziness, pallor, cold sweating, salivation, nausea, and vomiting.
Physiological mechanisms
Motion sickness may result from exposure to swinging, turning, rocking, or up-and-down movements. The disorder apparently stems from the contradictory data relayed to the brain during such motions by the eyes and by the balance centre within the non-acoustic portion of the inner ear, which must be functional for symptoms to develop. In each ear the three semicircular canals and the paired otolith organs participate in maintaining the body’s equilibrium and in the coordination of eye-head-body movements. These organs are stimulated continually by gravity and also by sudden linear accelerations. The eyes, by contrast, relay information to the brain about the body’s position and movement based on external surroundings rather than internal cues.
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Motion sickness arises when the vestibular system of the inner ear sends messages about body position or movement that are contradicted by the information sent by the eyes. An example of this is seasickness: the inner ear senses changes in linear and angular acceleration as the body bobs up and down with the movement of the ship, but, since the cabin bobs up and down in synchrony with the passenger, the eyes register a relatively stable scene. The brain becomes confused by these contradictory messages from different sensory receptors. In response, it stimulates the production of abnormally large amounts of the hormones epinephrine, norepinephrine, and vasopressin. After a few more minutes of exposure to motion, electrical rhythms in the muscles of the stomach accelerate markedly from a normal three cycles per minute to as much as nine per minute. By this time the visible symptoms of motion sickness are well advanced, and feelings of nausea may culminate in vomiting.
Prevention and treatment
Motion sickness is a self-limiting disorder, and prevention of the motion is the key to recovery in all cases. In cases where this is not possible, as in many travel situations, there are nevertheless several strategies for avoiding or mitigating the effects of the disorder. In cases of sustained exposure to motion, such as during sea voyages and space missions, many people can adapt to motion sickness after three or four days and feel progressively fewer symptoms. During shorter exposures, and depending on the situation, several different tactics can be helpful. The single most effective measure is to fix the body, especially the head, with reference to the vehicle.
Minimizing accelerations in a particular vehicle can involve altering factors such as seat location and time of day (e.g., in an aircraft) and cabin location and time of year (e.g., in a ship). The choice of vehicle for a given mode of travel may be important—e.g., flying above turbulence in a jet aircraft and the use of stabilizers in a ship. Sitting in a reclining posture, trying to avoid making turning movements of the head, closing one’s eyes, and focusing one’s gaze on relatively distant objects can also prove helpful. Motion sickness is also sometimes alleviated by concentrating on other tasks. Generally, unless vision is used to “lock” onto the horizon or to engage in activities resulting in distraction, there is less tendency to motion sickness if the eyes are closed. Reading and excessive eating or drinking tend to exacerbate the symptoms, as do anxiety and other stressful or painful emotional states. Certain illnesses, especially those with gastrointestinal symptoms, may increase one’s susceptibility to motion sickness. Given these suggestions, however, the prevention of motion sickness remains a highly individual matter.
Several drugs have been developed for the prevention or relief of motion sickness, though they often produce unwanted side effects. A combination of 1-scopolamine hydrobromide and dextroamphetamine sulfate, taken shortly before departure, affords some protection for several hours. Promethazine hydrochloride, with minimal risk of side effects, is a good substitute for scopolamine. Several drugs in the antihistamine category also decrease susceptibility to motion sickness, including diphenidol, dimenhydrinate, cyclizine, and meclizine. The last named is effective over periods up to 24 hours.
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