4. Describe with the aid of diagrams the pupillary light reflex. 
  • The light reflex pathway consisting of the ganglion cell output of the retina,which synapses with the neurons in the ipsilateral pretectal olivary nucleus. 
  • The neurons in the pretectal nucleus send crossed and uncrossed fibers to the neurons in the visceral portion of the Edinger-Westphal nucleus on both sides. 
  • These neurons form the preganglionic parasympathetic nerves that travel within the third nerve to synapse in the orbit at the ciliary ganglion.
  • Postganglionic parasympathetic nerve fibers pass from the ciliary ganglion to the eye through the short ciliary nerves to innervate the iris sphincter.
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