Sneezing is a normal response to irritation of sensitive tissues in the nasal passages. The irritant may be dust, pollen, chemicals, physical stimulation, infection, or similar causes. Some people sneeze when they are chilled, others when they pluck their eyebrows.
A common syndrome is "photic sneeze reflex". People with this trait can be stimulated to sneeze by bright light, such as emerging into sunlight or looking at the sun. This is a genetic trait that about 20%-30% of people have (at least based on European samples).The sneezing response is a complex one, involving stimulation of the nasal tissues, which are mediated by cranial nerves V and VII, and processing by a "sneeze center" in a distinct structure of the brainstem, thought to reside in the lateral medulla. Histaminic and muscarinic receptors there appear to affect the ability to sneeze. This region in turn seems to control the epipharyngeal, intrinsic laryngeal and respiratory muscles. The brain sends coordinated motor impulses along nerves controlling muscles of the abdomen, chest, diaphragm, neck, face, eyelids and various sphincters, as well as the mucus glands and blood vessels of the nose. All this happens automatically. (Further article here.)
Photic sneezing is an autosomal dominant trait. If you received the dominant gene from one or both of your parents, you will show this trait. This is similar to the hand-preference gene discussed in an earlier post. If you receive the dominant hand-preference gene from either or both of your parents, you will probably be right handed. So these are two behaviors that are encoded in your genes. (Another article here.)
(I am left handed, and I also have the photic sneezing trait. Coincidence? Probably.)
- There is a rare psychogenic syndrome of intractable "pseudosneezing" related to psychological stresses.
- You always close your eyes when you sneeze, like the man in this picture.
- People can't sneeze when they are asleep.
- 95% of people in one study sneezed and blew their noses less than 4 times a day when they didn't have colds.
- A typical sneeze can expel thousands of droplets at a speed of 150 km per hour or roughly 100 mph, with a range of up to a meter and a half.
- Thomas Edison used his early movie-camera technology to film the action of sneezes.
David Wheat's Science In Action site has articles about science and math in the real world, weird science, science news, unexpected connections, and other cool science stuff. There is an index of the articles by topic here.
tags: science, science education, math, education, Science In Action