The hormone epinephrine binds to β adrenergic receptors on smooth muscle cells of the bronchioles, causing them to dilate (increase in diameter). thyroid hormone is essential for the synthesis of β adrenergic receptors; therefore, in the absence of thyroid hormone, epinephrine cannot trigger bronchodilation. this concept is known as

stratosphere: as the altitude increases, the air temperature increases. the stratosphere has a layer of ozone, called the ozone layer. this layer absorbs most of the ultraviolet radiation from sunlight. this results in the stratosphere being warmer.

for  example, forests have higher evapotranspiration than other ecosystems,  such  as grasslands, because of their deeper roots and greater leaf area. thus forests have a net moistening effect on the atmosphere and become a moisture source for downwind ecosystems.