Final answer:
Norepinephrine is a hormone that increases heart rate, breathing rate, muscle contractions, blood pressure, and blood glucose levels. It also constricts smooth muscle in all blood vessels.
Step-by-step explanation:
Norepinephrine is a hormone that functions to produce a rapid response throughout the body in stressful situations. It is released by the adrenal medulla and the sympathetic division of the autonomic nervous system. Norepinephrine increases heart rate, breathing rate, muscle contractions, blood pressure, and blood glucose levels. It also constricts smooth muscle in all blood vessels.