MCQ – 99653

First order neurons in the visual pathway are constituted by:

A.	Bipolar cells
B.	Amacrine cells
C.	Ganglion cells
D.	Rods and cones

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Correct Answer � A Explanation

The visual pathway involves a multi-neuronal system beginning in the retina and ending in the visual cortex. Understanding the hierarchical structure of retinal neuron layers is crucial in identifying the correct order of neurons in the visual pathway.

Neuronal Layers in the Retina:

1. Photoreceptors (Rods and Cones) – These are the receptors, not neurons of the visual pathway.

2. Bipolar Cells – These are the first-order neurons that receive synaptic input from rods and cones and transmit it to ganglion cells.

3. Ganglion Cells – These are the second-order neurons, their axons form the optic nerve.

4. Lateral Geniculate Nucleus (LGN) Neurons – These are third-order neurons, projecting to the primary visual cortex.

Why Other Options Are Incorrect

B. Amacrine cells:

• These are interneurons in the retina that modulate signal transmission between bipolar and ganglion cells.

• They do not directly carry the signal along the visual pathway, and are therefore not first-order neurons.

C. Ganglion cells:

• These are the second-order neurons in the visual pathway.

• Their axons form the optic nerve, chiasma, and tract.

D. Rods and Cones:

• These are photoreceptor cells, not considered neurons in the pathway hierarchy.

• They transduce light into electrical signals but do not relay them to the brain directly.