Vasoconstriction

Vasoconstriction is the narrowing of a blood vessel due to the contraction of a surrounding muscle. It's a normal physiological response to bleeding, cold, or suddenly sitting up. It's also either the therapeutic or a side effect of many pharmaceuticals including antihistamines, decongestants, and stimulants. In most cases, vasoconstriction will raise local blood pressure in the affected area.
Vasoconstriction at Wikipedia
Category:Physiology