What effect does epinephrine have on cardiac activity?

What effect does epinephrine have on cardiac activity?

• A. Decrease heart rate
• B. No change
• C. Increase heart rate and blood pressure
• D. Decrease blood pressure

Answer: (C)

Epinephrine stimulates the sympathetic system to boost cardiac activity. In the heart it binds to beta-1 receptors, which increases the rate at which the SA node fires, speeds conduction through the AV node, and strengthens each heartbeat. This combination raises cardiac output by both a faster heart rate and stronger contractions. At the same time, epinephrine activates alpha-1 receptors on vascular smooth muscle, causing vasoconstriction and raising systemic vascular resistance, which elevates blood pressure. While beta-2 effects can cause some regional vasodilation, the overall effect is a rise in blood pressure. So the net effect is an increase in heart rate and an increase in blood pressure.

Epinephrine stimulates the sympathetic system to boost cardiac activity. In the heart it binds to beta-1 receptors, which increases the rate at which the SA node fires, speeds conduction through the AV node, and strengthens each heartbeat. This combination raises cardiac output by both a faster heart rate and stronger contractions. At the same time, epinephrine activates alpha-1 receptors on vascular smooth muscle, causing vasoconstriction and raising systemic vascular resistance, which elevates blood pressure. While beta-2 effects can cause some regional vasodilation, the overall effect is a rise in blood pressure. So the net effect is an increase in heart rate and an increase in blood pressure.