The aorta is innervated by a plexus of autonomic unmyelinated nerve fibers which ramify in the outer wall (adventitia) and approach the external smooth muscle cells of the media. These nerves conduct a regular flow of sympathetic impulses maintaining a variable “vasomotor tone”
The aorta has no vasodilator innervation and neurogenic vasodilation follows a reduction of sympathetic vasoconstrictor tone. The aorta receives direct sympathetic branches from nearby sympathetic ganglia. Lamellated (Pacinian) corpuscles, which are mechanoreceptors, occasionally appear in the aortic adventitia.