MadSci Network: Anatomy
Query:

Re: Does your heart stop when you sneeze?

Date: Wed Mar 25 23:07:35 1998
Posted By: Tom Wilson, M.D./PhD, Pathology, Div. of Molecular Oncology, Washington University School of Medicine
Area of science: Anatomy
ID: 887420441.An
Message:

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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