Describe what happens when light strikes a photoreceptor. Include the effects on photopigments and release of transmitter by photoreceptors.

What will be an ideal response?


In the dark, photoreceptors are active with sodium and calcium channels open. This depolarization of the membrane causes the release of glutamate, which in turn inhibits activity in the bipolar cells. When light is present, the photopigments within the photoreceptors absorb the light energy, causing some of the molecules to break down. This reaction of the photopigments causes the sodium and calcium channels to close. With the loss of inhibition, due to the closing of these channels and decrease in the release of glutamate, the bipolar cells become more activated and release more neurotransmitter. The release of neurotransmitter then activates the ganglion cells whose axons transfer the visual signals to the brain.

Psychology

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