When light strikes a receptor, does the receptor excite or...

Key Concepts

Lateral Inhibition

Lateral inhibition is a mechanism by which interconnected neurons inhibit their neighbors, thereby accentuating differences in stimulus intensity. In the retina, horizontal cells contribute to this phenomenon by modulating the signals of bipolar cells, thereby refining the spatial resolution and contrast of the visual information that is ultimately transmitted to higher visual centers.

Horizontal Cells

Horizontal cells are interneurons in the retina that integrate and regulate input from multiple photoreceptors. They play a key role in lateral inhibition by sending feedback to photoreceptors and feedforward signals to bipolar cells. This lateral inhibition is crucial for sharpening spatial responses and enhancing contrast in the visual signal.

Phototransduction

This is the process by which photoreceptors in the retina convert light into electrical signals. When light strikes a photoreceptor, it leads to a change in the cell’s membrane potential, typically causing hyperpolarization. This initial response sets the stage for further signal processing in the retinal circuitry.

Bipolar Cells

Bipolar cells receive signals from photoreceptors and are divided into different types (e.g., ON and OFF bipolar cells) based on their response to the changes in neurotransmitter release from photoreceptors. The decrease in glutamate release due to photoreceptor hyperpolarization has opposite effects on these two cell types, leading to either depolarization or hyperpolarization, which is fundamental for encoding light increments and decrements.

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