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Physiology & Medicine / Re: why do we get runny nose when we sneeze?
« on: 24/01/2018 07:44:21 »
There are several reasons why this may happen. The most likely is that the same stimulus that provoked the sneeze also provoked the runny nose, albeit more slowly in the latter case.
Specifically, the lining of the nose is richly endowed with mast cells; these are charged with histamine. When anything irritates or perturbs the mucosa (lining) - and this can be a viral or bacterial infection, inhaled dust or allergens, foreign bodies or parasites, these cells discharge their histamine cargo.
Histamine has several actions. One is to profoundly irritate the sensory nerves that supply the nose lining; this irritation can trigger a sneeze. Histamine is also vaso-active; that is, it acts on blood vessels to make them dilate and become leaky. This has the effect of increasing blood delivery to secretory glands in the mucosa. Histamine also directly triggers mucus production by these same glands. These latter actions take longer to initiate than a sneeze reflex; hence you sneeze first, then blow your nose later...
Specifically, the lining of the nose is richly endowed with mast cells; these are charged with histamine. When anything irritates or perturbs the mucosa (lining) - and this can be a viral or bacterial infection, inhaled dust or allergens, foreign bodies or parasites, these cells discharge their histamine cargo.
Histamine has several actions. One is to profoundly irritate the sensory nerves that supply the nose lining; this irritation can trigger a sneeze. Histamine is also vaso-active; that is, it acts on blood vessels to make them dilate and become leaky. This has the effect of increasing blood delivery to secretory glands in the mucosa. Histamine also directly triggers mucus production by these same glands. These latter actions take longer to initiate than a sneeze reflex; hence you sneeze first, then blow your nose later...
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