What effect does norepinephrine have on the body?

Norepinephrine is a critical neurotransmitter and hormone in the body, particularly involved in the fight-or-flight response. One of its primary effects is the constriction of blood vessels, which leads to an increase in systemic vascular resistance. This vascular constriction elevates blood pressure, making option C correct.

Norepinephrine works by binding to alpha-adrenergic receptors, which causes smooth muscle contraction in the blood vessels. This vasoconstriction is vital during stress or emergency situations, as it helps redirect blood flow to essential organs and muscles, enhancing the body's ability to respond effectively to immediate challenges.

In contrast, the other options do not accurately reflect norepinephrine's role in the body. It does not decrease blood pressure; rather, it increases it. Additionally, while norepinephrine can influence heart rate, its primary action does not include stimulating digestion, which is more associated with the parasympathetic nervous system. Lastly, norepinephrine does not inhibit the stress response; it is, in fact, a key player in facilitating and enhancing that response.