They are very sensitive, usually serving us well so that we can keep our balance as our bodies move. Put us in a boat on a rough seas however, and these sensors are overloaded, sending too much data, in strange patterns, to the brain. You may experience something very much like motion sickness, with balance problems, a feeling that the room is spinning, along with nausea and perhaps vomiting. Humans and animals have developed poison sensors which proved very useful as our ancestors explored new tastes around them. Those who ate the poison berries and vomited lived while those that ate them and did not vomit died.
Vomiting can be very useful.
Almost everybody at some time but some more often that others. You are most sensitive at about 12 years of age with declining susceptibility as you get older. Asians are generally more prone to seasickness. Women become ill more frequently especially when pregnant or near menstruation. You are at greater risk if you are fatigued, anxious, sleep-deprived and if you consume alcohol or certain medications.