Pathway for pupillary dilatation

What is the pathway for pupillary dilatation? 

This pathway has three neurons.

First-order fibers descend from the ipsilateral hypothalamus through the brain stem and cervical cord to T1 to T2.

They synapse on ipsilateral preganglionic sympathetic fibers, exit the cord, travel up the sympathetic chain as second-order neurons to the superior cervical ganglion, and then synapse on postganglionic sympathetic fibers.

The third-order neurons travel via the internal carotid artery to the orbit and innervate the radial smooth muscle of the iris.


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