What is motion sickness?

Motion sickness is associated with various forms of travel including air, sea, train or car travel. It is also possible to experience motion sickness when watching a movie in which dramatic movements are shown, but the body is motionless. Movement is detected by the vestibular system of the ear, which comprise the fluid filled canals in the inner ear. These detect motion or changes in the body’s position and send the information to the brain. If visual messages sent by the eye suggest that the body is still, this conflict causes the brain to interpret this discrepancy as an hallucination due to an ingested toxin that needs to be cleared from the system. This stimulates the area postrema of the brain to induce the vomiting reflex. Motion sickness is a neurological condition that is based on perception rather than a physical disorder.

How do antiemetics help with motion sickness?

Antiemetics like the anticholinergic scopolamine work by blocking specific receptors for acetylcholine in the vestibular system of the ear and in the brain. Stimulation of acetylcholine receptors is involved in the transmission of information from the vestibular system of the ear to the vomiting center in brain and from the brain to the stomach. The anticholinergic action of antiemetics like scopolamine prevents the vomiting reflex from being induced, which eases symptoms of motion sickness.
...Read more