A&P Blood Vessels Practice Test

Norepinephrine raises vascular tone and blood pressure mainly by activating α1 receptors on vascular smooth muscle, causing vasoconstriction that increases peripheral resistance. It also stimulates β1 receptors in the heart, increasing heart rate and contractility, which boosts cardiac output. The combined effect is a rise in blood pressure. It doesn’t cause vasodilation through β2 receptors, and while a reflex vagal response can occur if blood pressure rises, the direct actions of norepinephrine are to increase heart rate and force of contraction rather than decrease it.