Vasoconstriction characterizes the narrowing of blood vessels following the constriction of the smooth muscles lining their inner walls. This action is most pronounced in large veins and arteries and can be considered the functional opposite of vasodilation.
Vasoconstriction increases blood pressure, lowers cardiac output, and lessens blood flow either locally or at a systemic level. Vasoconstriction is especially important in helping reduce blood loss and protecting vital organs during hypothermic conditions.
Vasoconstrictive medications include common allergy medication, decongestants, and stimulants such as methamphetamine. One common side effect of vasoconstriction agents is pupil dilation.
Endogenous compounds responsible for vasoconstriction include the following:
- ATP (intra and extra-cellular)
- Hypoxia (low oxygen)