By Dr. Eddy M. del Rio
Dentists constantly remind patients to brush their teeth well, including the tongue. But as any brusher knows, an errant stroke to the back of the tongue triggers a gag reflex, which also causes the eyes to tear. But why should a stimulus applied in the oral cavity—the opening of the gastrointestinal tract—have any effect on the eyes? Could evolutionary mechanisms have caused the effect or does intelligent agency better explain it? Imagine if, when touching the tongue, one would always hear a particular bell tone, or smell an aroma, or feel the hands or feet become cold as ice or hot as fire, or see temporarily only in hues of black and white? Such anomalous crossings of stimulation with sensation are termed synesthesia. Viewed differently, imagine the engine in a car becoming hotter, but instead of the coolant gauge rising, the radio volume becomes louder. Such a phenomenon would surely send the owner back to the dealer for some warranty repairs. But when the human eyes tear because we have been gagged, it is not an anomaly but a normal function. How did this process come about?
Reflex tearing has been well understood for decades.1 It refers to tearing in response to tactile stimulation of the surface of the eye.2 Bogorad’s syndrome,3 colloquially known as “crocodile tears syndrome,” is an anomaly of function due to damage of the facial nerve that results in tearing not when touching the eye, but when the sufferer simply eats. Here, a normal phenomenon is triggered in a way entirely different from what might be expected. Though scientists have understood the anatomy and physiology of reflex tearing, how it came about is quite another matter. What purpose could there be for what I shall call the gag lacrimal gland reflex (GLGR)?
Consider that a gag reflex is frequently associated with a violent expulsion of the stomach’s contents, or vomiting (emesis). The stomach, in addition to digestive enzymes called proteases, contains hydrochloric acid (also known as muriatic acid), which “is a highly corrosive, strong mineral acid with many industrial uses.”4 If the ailing person gets some of this mix on the skin quick action should be taken to prevent injury—yet this “alien-blood-like” stuff doesn’t burn a hole in the stomach. Now, when one vomits one also reflexively bends over, bringing the mouth closer to the ground. Also, the force of the expulsion may result in splashing of the acidic mix, thereby leaving the eyes vulnerable to injury. But we humans need not worry because our lacrimal glands spring into action by emptying their stores—effectively hosing down our eyes with tears to help protect them.
This elegant process demonstrates every bit of the same understanding, forethought, and purpose that an aviation emergency response team does…
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