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Cranial nerves that transmit parasympathetic fibers are oculomotor, facial, glossopharyngeal and vagus nerves. Oculomotor nerve controls constrictor pupillae of iris and ciliary muscle by supplying parasympathetic fibers to it. Facial nerve supplies parasympathetic fibers to sublingual and submandibular glands where as glossopharyngeal nerve supplies parasympathetic fibers to the parotid gland. Lastly, vagus nerve parasympathetic fibers regulate heart rhythm and supply the smoot muscle of gastro intestinal tract, bronchi and trachea.