Parasympathetic system and bronchoconstriction

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lazybutt26

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Hi guys!

Please help. I understand that sympathetic NS causes vasoconstriction and parasympathetic NS causes vasodilation. But in respiratory system, this pattern seems to be the opposite.
Parasympathetic system causes bronchoconstriction. Now, I know the definition of bronchoconstriction. I just need an understanding of why this happens. Because it doesn't make any sense to me.
When broncoconstriction happens, the airway gets narrowed and this causes trouble breathing right? as seen in Asthma patients with weezing and coughing. But, parasympathetic system is associated with relaxation..why would it ever cause the broncoconstriction instead of dilation? It seems to me that sympathetic NS would make more sense to cause broncoconstriction because sympathetic NS is associated with hyperventilation and vasoconstriction....

So confused, I don't even know what I wrote up there.

Please help!

Thanks in advance !

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When your bronchioles are constricted, they can't store that much air and if you're in fight-or-flight mode, you want to have as much lung capacity as possible. So the sympathetic response causes bronchodilation. Now, the parasympathetic system reverses the effects of the sympathetic. Therefore, it has to reverse the bronchodilation and it does so by bronchoconstriction. It's not supposed to constrict the bronchioles to pathological levels but rather simply to reverse bronchodilation.
 
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O my gosh. Thank you so much! That's what I was thinking too. It did not make sense to have bronchioles constricted in relaxed state. I thought of it as the reverse effect of bronchodilation. Great! Thanks for your help :)
 
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