What are ON-bipolar cells?

What are ON-bipolar cells?

• A. Cells activated when neurotransmitter fails, leading to ganglion cell firing
• B. Cells activated by neurotransmitter release, inhibiting ganglion cells
• C. Cells that transduce light into electrical signals independently of photoreceptors
• D. Cells that directly generate action potentials to the brain

Answer: (A)

ON-bipolar cells form part of the retina’s ON pathway. They depolarize when light reduces the glutamate released by photoreceptors. In darkness, glutamate binds to mGluR6 receptors on ON-bipolar cells and keeps them inhibited. When light hits, glutamate release falls, lifting that inhibition and causing the ON-bipolar cells to depolarize and drive ON-center ganglion cells toward firing. They signal with graded potentials rather than generating their own action potentials, and they rely on input from photoreceptors for light detection. The described behavior—being activated by a decrease in neurotransmitter release, which leads to ganglion cell firing—best matches how ON-bipolar cells operate.

ON-bipolar cells form part of the retina’s ON pathway. They depolarize when light reduces the glutamate released by photoreceptors. In darkness, glutamate binds to mGluR6 receptors on ON-bipolar cells and keeps them inhibited. When light hits, glutamate release falls, lifting that inhibition and causing the ON-bipolar cells to depolarize and drive ON-center ganglion cells toward firing. They signal with graded potentials rather than generating their own action potentials, and they rely on input from photoreceptors for light detection. The described behavior—being activated by a decrease in neurotransmitter release, which leads to ganglion cell firing—best matches how ON-bipolar cells operate.