Ans. d. Postganglionic sympathetic fibres from cervical sympathetic chain (Ref: Gray 39/e p710; Parson 20/e p33)Dilator iridis (pupillae) is supplied by postganglionic (nonmyelinated) fibres from superior cervical sympathetic ganglia."Dilator papillae is supplied with non-myelinated post ganglionic fibers from the superior sympathetic ganglion."- (Ref: Gray 39/e p710)"Dilator pupillae is supplied by adrenergic fibers of cervical sympathetic nerves. The dilator tract probably commences in hypothalamus not far from constrictor centre and also has connection with cerebral cortex."- (Ref: Parson 20/e p33) Parasympathetic (cholinergic) pathway to sphincter pupillaeSympathetic (adrenergic) pathway to dilator iridis (pupillae)NucleusFibers start from Edinger-Westphal nucleus near the 3rd nerve nucleus in floor of aqueduct of sylvius1st order neuron from hypothalamus till ciliospinal (Budge) center in interomediolateral columns of C8-T1PreganglionicNeuronThrough occulomotor (3rd) nerve2nd order preganglionic neuron from budge ciliospinal center to superior cervical ganglion in neck (cervical sympathetic neurons).GangliaCiliary ganglionQSuperior cervical ganglionQPost-ganglionic neuronShort ciliary nerve3rd order post ganglionic fibers arising from superior cervical ganglion, ascends carotid plexus (along internal carotid artery) to enter skull where they join nasociliary branch of trigeminal nerve.SupplySphincter papillaeDilator iridis (pupillae)Q