Key Points

• Only one small region of retina, the fovea, provides high visual acuity because the foveal arrangement of photoreceptors places the light-sensitive cellular elements in direct alignment with focused, incoming light.

• Cone photoreceptors are specialized for high-acuity color vision under bright-light (photopic) conditions, whereas rod photoreceptors have more sensitivity but less acuity and are specialized for dim-light (scotopic) vision.

• The retinal pigment epithelium provides a number of crucially important support roles for photoreceptors, including removal of cellular debris and recycling of molecular substrates in the visual transduction cascade.

• The absorption of light by photopigments in rods and cones triggers a phototransduction cascade that ultimately determines the rate at which glutamate is released from photorecep-tor terminals.

• A three-neuron chain consisting of photoreceptor, bipolar, and ganglion cells transmits visual information through the retina, the optic nerve and track, and on to higher visual centers.

• The receptive field of any given neuron in the visual pathway is defined as the portion

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Get Rid of Gallstones Naturally

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