In the retina, photons are converted into electrical signals in what form?

In the retina, photons are converted into electrical signals in what form?

• A. Photons are converted into graded potentials
• B. Photons are converted into chemical signals
• C. Photons are converted into action potentials
• D. Photons are converted into graded potentials and action potentials

Answer: (D)

Photons trigger phototransduction in the retina, starting with a chemical change in the photopigment of rods and cones. This chemical event modulates ion channels, causing graded changes in membrane potential rather than a single all‑or‑none spike at the photoreceptor itself. The resulting signal—an intensity-dependent release of neurotransmitter onto downstream neurons—is carried along the retinal circuitry as graded potentials in the photoreceptors and bipolar/horizontal cells. As this signal travels toward output cells, the final step involves retinal ganglion cells, which convert the graded synaptic input into action potentials that travel down the optic nerve to the brain. So, photons are ultimately represented in the retina as both graded electrical signals (in photoreceptors and other early retinal neurons) and action potentials (in ganglion cells) as the information exits the retina.

Photons trigger phototransduction in the retina, starting with a chemical change in the photopigment of rods and cones. This chemical event modulates ion channels, causing graded changes in membrane potential rather than a single all‑or‑none spike at the photoreceptor itself. The resulting signal—an intensity-dependent release of neurotransmitter onto downstream neurons—is carried along the retinal circuitry as graded potentials in the photoreceptors and bipolar/horizontal cells.

As this signal travels toward output cells, the final step involves retinal ganglion cells, which convert the graded synaptic input into action potentials that travel down the optic nerve to the brain. So, photons are ultimately represented in the retina as both graded electrical signals (in photoreceptors and other early retinal neurons) and action potentials (in ganglion cells) as the information exits the retina.