Explain how epinephrine ( a catecolamine) will cause some blood vessels to constrict but other vessels to dilate?

-Because epinephrine can bind to different receptors and can activate different signalling pathways with varying responses.

Explanation:

Epinephrine is a hormone, synthezied and secreted by adrenal gland during stress conditions. Epinephrine leads to vasoconstriction of many blood vessels, while it leads to dilation of blood vessels in liver and skeletal muscle cells.

This is because epinephrine has ability to bind with both alpha- and beta-adrenergic receptors, which are present in different target cells or organs. As both receptors involve different signalling pathways which leads to generation of different responses on target organs or tissues.

Thus, epinephrine shows different responses in different target organs.