Under normal circumstances, bronchoconstriction is caused by and bronchodilation is caused by .

Under normal circumstances, bronchoconstriction is caused by Parasympathetic nervous system and bronchodilation is caused by sympathetic nervous system

Explanation:

bronchoconstriction is simply a  a tightening,  narrowing or constriction of the  of brochioles ( airlways) that increase in mucous secretion  and it may occour due to coughing, sneezing  or any other factors.while bronchodilaiton is the relaxation  or the dilation of the bronchioles (airways in the lungs) that  decrease of mucous secretion

An  increase in parasympathetic activity causes BRONCHOCONSTRICTION,  a decrease in parasympathetic activity causes BRONCHODILATION.  There is no sympathetic innervation of the bronchiole smooth muscle!

The  effect of the Smooth muscle contraction  usually may cause bronchoconstriction  to decline or decrease in the diameter of the bronchioles while  the effect or the result of the smooth muscle relaxation  may cause  bronchodilation  to increase in the diameter of the bronchioles. Therefore,  Parasympathetic stimulation leads to bronchoconstriction and  sympathetic stimulation leads to  bronchodilation.

well, there are a lot of places we get information about earth from. like science classes, websites, books, newspapers, etc.

c- companies fail to take environmental protection into account. i think