What is a vasoconstrictor?

A vasoconstrictor is an agent that causes blood vessels to constrict, which means it narrows the diameter of the blood vessels. This action results in an increase in blood pressure and a reduction in blood flow to certain areas of the body. Vasoconstrictors are often used in medical settings to manage bleeding, reduce swelling, or raise blood pressure in patients experiencing shock. By constricting blood vessels, these agents effectively limit blood flow to regions where it may be less critical, preserving it for vital organs.

The other options describe different physiological effects: an agent that causes muscles to relax is associated with muscle relaxants, an agent that dilates the airways pertains to bronchodilators used in treating respiratory conditions, and an agent that increases blood flow would refer to vasodilators, which have the opposite effect of vasoconstrictors. Understanding these terms is crucial for recognizing their applications in both dental practice and broader medical treatments.