Which is the first order neuron in optic pathway?
Rods and cones are the photoreceptors. The synaptic body is the poion of rods and cones that connects with subsequent neuronal cells, the horizontal and bipolar cells. The bipolar cells, which transmit signals veically from the rods cones and the horizontal cells to the inner plexiform layer, where they synapse with ganglion cells and amacrine cells. Thus bipolar cells are the cells which take away signals from the photoreceptors, hence they are the first order neurons. Ref: TEXTBOOK OF MEDICAL PHYSIOLOGY GUYTON AND HALL, 12e Page no 750, 744.
Bipolar cells
Ganglionic cells
Cells of lateral geniculate body
Astrocytes
Nervous system