Question:medium
Which are the first order neurons in the optic pathway?
Which are the first order neurons in the optic pathway?
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Count the relay neurons starting from the receptor: receptor, then bipolar cell.
Updated On: Jun 24, 2026
- Bipolar cells
- Ganglionic cells
- Cells of lateral geniculate body
- Astrocytes
Show Solution
The Correct Option is A
Solution and Explanation
Step 1: Trace the relay of impulses from the eye to the brain. Light first strikes the rods and cones, which act as the sensory receptor layer of the retina.
Step 2: From the receptors, the signal passes to the bipolar cell. By definition the bipolar cell is the first neuron in the relay chain, so it is the first order neuron.
Step 3: The relay then continues to the ganglion cell (second order), whose fibres travel through the optic nerve, chiasma and tract, and finally to the neurons of the lateral geniculate body (third order) that project as optic radiations.
Step 4: Astrocytes only provide structural and metabolic support and never relay vision. Therefore the first order neuron is the bipolar cell.
\[\boxed{\text{Bipolar cells}}\]
Step 2: From the receptors, the signal passes to the bipolar cell. By definition the bipolar cell is the first neuron in the relay chain, so it is the first order neuron.
Step 3: The relay then continues to the ganglion cell (second order), whose fibres travel through the optic nerve, chiasma and tract, and finally to the neurons of the lateral geniculate body (third order) that project as optic radiations.
Step 4: Astrocytes only provide structural and metabolic support and never relay vision. Therefore the first order neuron is the bipolar cell.
\[\boxed{\text{Bipolar cells}}\]
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