Vasodilation is where blood vessels widen. It results from relaxation of muscle cells within blood vessel walls. The process is essentially the opposite of vasoconstriction, which is the narrowing of blood vessels.
When vessels widen, blood flow is increased. This in turn decreases blood pressure. Drugs that cause vasodilation are called vasodilators.
- "Definition of Vasodilation". MedicineNet.com. 27 April 2011. Retrieved 13 January 2012.