What is Vasoconstriction?
[[File:Blood vessels-en.svg|thumb|Diagram of blood vessels.]] '''Vasoconstriction''' occurs when [[blood vessel]]s become narrower because of the tightening of the muscles in their walls. Its opposite is [[vasodilation]], which is when blood vessels widen.<ref>{{cite web| title = Definition of Vasoconstriction| publisher = MedicineNet.com| date = 19 March 2013| url = http://www.medterms.com/script/main/art.asp?articlekey=5964| accessdate = 14 August 2013| archive-date = 16 December 2013| archive-url = https://web.archive.org/web/20131216184232/http://www.medterms.com/script/main/art.asp?articlekey=5964| url-status = dead}}</ref> For example, when you are cold, blood vessels near the skin vasoconstrict so that you don't lose too much heat from your blood. When blood vessels vasoconstrict, this increases [[blood pressure]]. Sometimes, blood pressure is too high and this can cause [[heart disease]], so people have to take [[medicine]] to make the muscles in the blood vessels relax. ==References== {{reflist}} {{biology-stub}} [[Category:Blood vessels]]