What is the process called when blood vessels narrow to limit blood flow?

The process where blood vessels narrow to limit blood flow is known as vasoconstriction. This physiological response is essential for regulating blood pressure and redistributing blood flow to vital organs during times of stress or low oxygen levels. When vasoconstriction occurs, the smooth muscles in the blood vessel walls contract, leading to a decrease in the diameter of the vessels. This action increases the resistance against which the heart must pump, which can result in higher blood pressure.

Vasodilation, on the other hand, refers to the widening of blood vessels, which would increase blood flow rather than restrict it. This contrast highlights the specific function of vasoconstriction in maintaining homeostasis within the cardiovascular system. Other terms like vein constriction and fluid restriction are not standard terms in the context of blood vessel physiology; they don't accurately describe the narrowing of blood vessels or the processes involved in regulating blood flow.