|MadSci Network: Anatomy|
In a word, no, your heart does not stop when you sneeze. From my perspective, it is hard to even imagine what this would mean. A sneeze itself is really a very brief event, occurring in a shorter time then a heartbeat. Of course, there is the building up to the sneeze (the "ah" of the "ah-choo"), but the heart certainly does not stop beating because of this ah-ing. Check your pulse next time to prove this to yourself. As I answer this question, I am trying to imagine just how the heart might even "know" that you are sneezing. The heart beats because a small part of it called the SA node has a "pacemaker" activity. What this means is that there is a type of electrical cycle going on that triggers beats roughly once every second. Sneezing does not change this electrical cycle, so the heart keeps beating. Said a different way, the muscle of your heart is a big mass of electrically active tissue, and this electrical activity will not stop because of a sneeze, or anything else for that matter. And yet, a sneeze is definitely a complex cardiovascular event. As you "ah" and "choo", you significantly change the pressure inside your chest, which in turn affects blood flow and thus the beating of the heart. Still further, I assume that a sneeze involves a significant activation of certain pathways of the "autonomic" (roughly means automatic) nervous system. These also innervate the heart and do affect the frequency and other aspects of the heartbeat. So MAYBE the rapid culmination of these inputs OCCASIONALLY causes the heart to "skip a beat" after a sneeze. Notice I did not say "stop". We all experience skipped beats once in a while, some more than others. You may notice it as a "fluttering" in your chest, a sensation that generally evokes a bit of anxiety. What happens is that there is occasionally a discoordination of the normally organized pathways of electrical activity in the heart. Sometimes one part of the heart does not conduct the beat appropriately, or more commonly, another part actually manages to beat ahead of schedule, thus throwing the whole beat off. Either way, you get one beat that does not occur correctly. But all this means is that you have to wait for the beginning of the next electrical cycle to come around, at which time a normal, organized beat will occur (assuming that we are talking about a normal heart!). You see, the heart didnít stop, really, since the electrical cycle was still ongoing. It just got out of synch for a while. Again, I am not actually aware that this happens with any increased frequency after a sneeze, but I suppose it is possible. Taking a more historical/philosophical view of your question, the much more likely explanation for why people say "God bless you" has to do with religious beliefs and superstition. As I understand it, in earlier times it was believed that when you sneezed you opened yourself, or your soul, to the outside world. It was an unnatural and certainly a bizarre happening, and clearly portended evil. I am certain that there are variations on this theme, but basically it was thought that your soul might escape, or demons and evil spirits might get in, or even that they may have caused the sneeze in the first place. The blessing was to help ward off such badness. I am no historian, but I think people have done fairly extensive studies of this custom, its variations, and its origins. As a final thought, I think the most interesting question is not why we say "God bless you", but rather why we sneeze in the first place! I wrote a Mad Scientist answer about this a while back that I am still trying to fully satisfy myself about. Ah, well. Or maybe I should say, Ah choo. Tom Wilson, MD PhD View another Mad Scientist Network answer related to sneezing here.
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