Innervation of blood vesse Sympathetic vasoconstrictor fiber (contin.) >Almost all vessels. such as arteries arterioles venules and veins are innervated >except the capillaries, precapillary sphincters and most of the metarterioles >Tone: Usually the sympathetic vasoconstrictor fibers keep tonicInnervation of blood vessels ➢Sympathetic vasoconstrictor fiber (contin.) ➢Almost all vessels, such as arteries, arterioles, venules and veins are innervated, ➢except the capillaries, precapillary sphincters and most of the metarterioles. ➢Tone: Usually the sympathetic vasoconstrictor fibers keep tonic