What happens when blood vessels contract?

What happens when blood vessels contract?

Blood vessels are broadly of three types: arteries which carry oxygenated blood, veins which carry deoxygenated blood back to the heart and capillaries, the tiny vessels which connect arteries and veins, in the organs. Of these, the most likely to contract are the arteries as they have a muscular wall with smooth muscles (involuntary muscles). The contraction of the arteries are not under voluntary control. They can occur during stress due to overactivity of the sympathetic nervous system. When the arteries, contract (spasm), the territory supplied by that artery suffers ischemia (lack of blood supply). This can lead to damage of the cells in that region. If blood vessels contract for a prolonged period, blood supply to the region will be affected and cause pain.

If it is a limb which is involved, there can be pain, loss of sensation, muscle weakness, the limb becomes pale and pulseless (Five Ps of critical limb ischemia). Ischemia is the technical term for reduction in blood supply.

If the blood vessels supplying the heart muscle (coronary arteries) undergo spasm, chest pain and abnormal heart rhythms can occur. Severe contraction of multiple coronary arteries can cause significant damage to the heart muscle, if the spasm is prolonged. Spasm of the blood vessels over the head can lead to headache known as vascular (related to blood vessel) headache or migraine.