That smooth muscle tissue is regulated in part by the nerve fibers of the autonomic nervous system, which can decrease the diameter of the lumen by contracting this middle layer during vasoconstriction, or expand it by relaxing during vasodilation.

平滑肌组织部分由自主神经系统的神经纤维调节，自主神经系统可以在血管收缩时通过收缩中间层来减小管腔直径，或者在血管舒张时通过放松来扩大管腔直径。