The popular belief that your heart stops when you sneeze is actually just a myth. When you sneeze, a lot of pressure builds up in your chest for a brief moment and it is plausible that the pressure could temporarily affect your blood pressure and heart rate. However, that pressure does not cause a heart to stop beating. Rather, your heart beat is kept steady by a continuous cycle of electrical signals automatically generated by your body. Essentially, your heart has a built-in pace maker that makes sure your heart maintains a regular beat at all times. If you are wondering why people say "bless you" after someone sneezes, I believe it stems from an old belief that bad spirits can enter into your body and soul when you sneeze. I think there are several versions of this, but that's the gist of it.

Actually that seems to be a myth!! According to an MD/PhD at Washington University, a sneeze does not stop the heart. The heart is on automatic control by your body and something like a sneeze would not stop the heart from contracting/relaxing. However, it is possible that occasionally your heart may "skip a beat" due to a change in pressure in your chest as you sneeze. This change in pressure could affect blood flow. However, it does not stop the heart from beating. Think of it more like a slight disruption in traffic flow through your heart. Hope that helps!!