Vasomotor

Vasomotor refers to actions upon a blood vessel which alter its diameter. More specifically, it can refer to vasodilator action and vasoconstrictor action.

==Control== ===Sympathetic innervation=== Sympathetic nerve fibers travel around the tunica media of the artery, secrete neurotransmitters such as norepinephrine into the extracellular fluid surrounding the smooth muscle (tunica media) from the terminal knob of the axon. The smooth muscle cell membranes have α and β-adrenergic receptors for these neurotransmitters. Activation of α-adrenergic receptors promotes vasoconstriction, while the activation of β-adrenergic receptors mediates the relaxation of muscle cells, resulting in vasodilation. Normally, α-adrenergic receptors predominate in smooth muscle of resistance vessels.