Vasoconstriction is the process in which blood vessels narrow, reducing blood flow to certain areas of the body. This occurs when the smooth muscles in the walls of the blood vessels contract, often in response to cold temperatures or stress. The body uses vasoconstriction to maintain blood pressure and redirect blood to vital organs. This physiological response is regulated by the nervous system and various hormones, such as norepinephrine. Vasoconstriction can help conserve heat in cold environments and is also involved in the body's response to injury, helping to minimize blood loss by reducing blood flow to damaged areas.