Question

Which are the first order neurons in the optic pathway?

• A. Bipolar cells
• B. Ganglionic cells
• C. Cells of lateral geniculate body
• D. Astrocytes

Hint:

Count the relay neurons starting from the receptor: receptor, then bipolar cell.

Answer 1

The Correct Option is A

Step 1: The visual pathway begins at the photoreceptors (rods and cones) of the retina, which capture light and convert it into a neural signal. These photoreceptors then synapse with the bipolar cells.

Step 2: The first order neuron is the bipolar cell of the retina. Its axon carries the impulse from the photoreceptor layer toward the ganglion cell layer.

Step 3: The second order neuron is the ganglion cell. Its axons form the optic disc, optic nerve, optic chiasma and optic tracts. The third order neuron lies in the lateral geniculate body, and its axons form the optic radiation that reaches the visual cortex.

Step 4: Hence the correct answer is bipolar cells. Ganglionic cells are second order, lateral geniculate body cells are third order, and astrocytes are supporting glial cells, not part of the conducting chain.