**Core Concept**
Action potentials are rapid changes in membrane potential that occur in response to a threshold level of excitation. In the retina, action potentials are generated by the transmission and processing of visual information from the photoreceptors (rods and cones) to the optic nerve. The retina is unique in that it is the only part of the central nervous system where action potentials are not generated by the initial sensory transducers (photoreceptors).

**Why the Correct Answer is Right**
Ganglion cells are the only neurons in the retina that generate action potentials. They receive excitatory synaptic inputs from bipolar cells and amacrine cells, which are processed through voltage-gated sodium channels. The action potentials generated by ganglion cells are then transmitted to the optic nerve as visual information is transmitted to the brain. This is in contrast to rods and cones, which generate graded potentials in response to light, and bipolar and amacrine cells, which also generate graded potentials. The action potential generation by ganglion cells allows for the rapid transmission of visual information.

**Why Each Wrong Option is Incorrect**
**Option A:** Rods and cones generate graded potentials in response to light, which are not action potentials.
**Option B:** Bipolar cells also generate graded potentials in response to synaptic inputs from photoreceptors, but do not generate action potentials.
**Option C:** Amacrine cells generate graded potentials in response to synaptic inputs from bipolar cells and other amacrine cells, but do not generate action potentials.

**Clinical Pearl / High-Yield Fact**
The retina is a unique part of the central nervous system where action potentials are not generated by the initial sensory transducers (photoreceptors). This is because the retina is designed to process visual information in a way that is optimized for low light levels, and the graded potentials generated by photoreceptors are sufficient for this purpose.

**✓ Correct Answer: D. Ganglion cells**