Narrowing of the arteries is often associated with heart disease and heart attacks. In fact, narrowing of blood vessels can also affect various other organs of the body, not just the heart. Blood vessels are tubular-like organs found throughout the body, from the toe to the tip of the head. The main function of blood vessels is to regulate blood pressure and drain blood throughout the body. Naturally, blood vessels can narrow (constriction) or dilate (dilation) due to the effect of muscle activity on the walls. Causes of narrowing of the veins Narrowing of blood vessels can occur naturally to regulate blood supply and blood pressure in certain body parts. Blood vessels can also be narrowed when you are in a cold place or have temperatures lower than body temperature. When there is a narrowing of blood vessels, the blood supply becomes slower, but the pressure becomes greater. Besides occurring naturally, narrowing of the arteries can also be caused by external factors, including