Which statement is true regarding the action of norepinephrine?

Norepinephrine primarily acts as a vasopressor and is critical in regulating blood pressure and systemic vascular resistance. When norepinephrine is released, it mainly stimulates alpha-1 adrenergic receptors, which leads to vasoconstriction of blood vessels. This constriction increases systemic vascular resistance, thereby raising blood pressure. This action is significant during situations of stress or shock when the body requires increased blood flow to vital organs.

The other statements are less accurate in this context. For example, norepinephrine has a minimal effect on beta-2 receptors, which are primarily associated with vasodilation in peripheral blood vessels. While it does impact heart rate, its predominant role is in raising blood pressure through increased vascular resistance rather than decreasing heart rate. Therefore, the assertion about norepinephrine raising systemic vascular resistance is true and captures its primary physiological action effectively.