Vasoconstriction is the narrowing of the blood vessels resulting from contraction of the muscular wall of the vessels, particularly the large arteries and small arterioles. The process is particularly important in staunching haemorrhage and acute blood loss. The process is the opposite of vasodilation, the widening of blood vessels. Dilation of arterial blood vessels causes a decrease in blood pressure. Smooth muscles of the vessel wall are controled by the sympathetic system. Vasomotor tone is maintained with high firing rate of sympathetic nerve. Low rate of firing results in dilation of the vessel. Scientifically accurate. Great for school science lab, doctor offices, clinic, hospital,... for educational purposes. Vector file scaleable to any size without losing resolution. Check out my store for more medical illustrations, both serious and fun stuffs. All images are made by myself, a scientist. If you cant find what you need here, just drop me a comment.