Vascular tone refers to the degree of constriction or relaxation of blood vessels, particularly the arteries and veins. It is primarily regulated by the smooth muscle in the vessel walls, which can contract or relax in response to various signals. This regulation helps control blood flow and blood pressure throughout the body. Changes in vascular tone can occur due to factors such as hormones, nervous system activity, and local metabolic conditions. For example, during exercise, increased demand for oxygen leads to the relaxation of blood vessels in the muscles, enhancing blood flow. Conversely, stress can cause constriction, raising blood pressure.