PATHOLOGY

Detailed explanation-1: -Blood flow is regulated by vasoconstriction or vasodilation of smooth muscle fibers in the walls of blood vessels, typically arterioles. This regulation can be systemic, affecting the whole of the circulatory system, or localized to specific tissues or organs.

Detailed explanation-2: -The site of local regulation of blood flow is the microcirculation, which is composed of a network of blood vessels-arterioles, capillaries and venules-whose functions are regulation oftissueperfusion and exchange of substances between blood and tissue.

Detailed explanation-3: -Constriction of venous (capacitance) vessels increases venous blood pressure and increases cardiac preload and cardiac output by the Frank-Starling mechanism, which increases arterial pressure. Because vasoconstrictor drugs increase arterial pressure, they comprise a functional group of drugs known as pressor drugs.