Type of Nerve:	Sensory
Chief Function(s) of Nerve:	Vision

The optic nerve , cranial nerve II, transmits visual information to occipital cortex.  The nerve is easily found by locating a large "X-shaped" structure just caudal to the olfactory bulbs. The fibers anterior to the intersection of the "X", are optic nerve fibers.  Axons caudal to the intersection, called the optic chiasm, are optic tract fibers.

Take time now to consider these facts:

• Axons from retinal cells in the lateral portions of the retina project to the optic chiasm, but they do not cross the midline.  They remain ipsilateral and travel to occipital (visual) cortex on the ipsilateral side.
  
  
• Axons from the medial, or nasal, regions of the retina enter the optic chiasm, cross the midline and project to the contralateral occipital cortex.


Do you understand where the fibers originate and how some cross over as they begin their journey to occipital (visual) cortex?  Stop now, and draw a figure that demonstrates how these fibers project to occipital cortex.  Be certain that you are clear on the difference between optic nerve, optic tract, and optic chiasm.  Make certain that you are clear about the type of fibers carried in each (i.e., whether they are ipsilateral, or contralateral fibers, or both)