Heart
Rate
Contractile
Force
TPR Blood
Pressure
Isoproterenol Increases due to activation of beta1 receptors in SA and AV nodes Increases due to activation of beta 1 receptors on myocardial cells. Decreases due to activation of beta 2 receptors cardiac output x total peripheral vascular resistance
Norepinephrine Decrease due to reflex increase in vagal tone on SA and AV nodes Increases due to effects on beta1-ARs on myocardial cells Increases due to activation of alpha1-ARs on vascular smooth muscle cells Increases due to effects on total peripheral vascular resistance
Low Doses of Epi Increases due to beta1-ARs on SA and AV nodal tissues Increases due to activation of beta1-ARs on myocardial cells Decreases due to preferential activation of beta2-ARs, at these doses there would be little activation of alpha1-ARs Similar to isoproterenol; the net effect will be the activity seen on cardiac output and total peripheral vascular resistance
High Doses of Epi Similar to the effects of norepinepherine Increases due to beta1-ARs on myocardial cells Increases due to activation of alpha1-ARs on vascular smooth muscle cells. Notice how at this dose the predominate effect is via the alpha1-ARs not the beta2-AR mediated decrease in total peripheral vascular resistance. Increases due to activation of alpha1-ARs on vascular smooth muscle cells