Q: Why does the administration of norepinephrine decrease the heart beat, while epinephrine increases it? Even though both have similar function of the contractility of the heart?

A:Norepinephrine acts on & Alpha receptors which are located in the peripheral arteries. Well Epinephrine has a predominant action on beta receptors which are located in the heart. The action of beta receptors is to increase the heart rate as well as its force of contraction well Norepinephrine constricts the smaller blood vessels of the body thereby increasing the blood pressure.