Point 6










Sympathetic PathwaysThe preganglionic sympathetics pass to the sympathetic trunk via the white communicating rami. They can synapse in the autonomic trunk (paravertebral ganglia), go up or down and synapse, or go through to comprise the splanchnics. Preganglionic sympathetics from spinal levels T1 to T5 ascend to the superior cervical ganglion, but most of these fibers arise from T1. Cells in the superior cervical ganglion (which receive their main drive from cells in the lateral horn at spinal level T1) then innervate, via postganglionic sympathetics, the smooth muscle of the dilator pupillae, the smooth muscle of the upper eye lid, the blood vessels, sweat glands, and hair of the head and face. A LESION at spinal level T1, either in the spinal cord or the ventral root, interrupts the sympathetic drive to these structures. This results in what is called HORNER'S SYNDROME. On the side IPSILATERAL to the spinal T1 lesion there is a drooping eyelid (PTOSIS), a constricted pupil (MIOSIS; remember, the boring parasympathetics are "in charge"), and a flushed (vasodilatation, since sympathetics to the skin vasoconstrict) and dry face.