Optic nerve is: September 2009

Ans. B: 2nd order neuron In the case of the optic nerve and tracts there are three separate neurons linked together, extending from the retina to the occipital coex. The sensory end-organ consists of the rods and cones. The first neuron begins in the outer plexiform or granular layer, and ends in the inner plexiform or granular layer. The cell-body governing the nutrition of this fiber is the bipolar cell, which cells forms the inner nuclear layer. This neuron, although extremely sho is the true optic nerve in the physiological sense, and corresponds to the long fiber which runs from the sole of the foot up into the spinal cord. The second neuron in the retina begins in the inner nuclear layer and runs from here up to the primary optic ganglia, i.e., chiefly the external geniculate body. This is the anatomical optic nerve. The cell governing the nutrition of this fiber is the ganglion cell.