Chapter 2 Summary

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1.   This chapter provided some insight into the complex journey that is required for us to see stars and other spots of light. The path of the light was traced from a distant star through the eyeball and to its ----- absorption transduction by photoreceptors and its ----- absorption transduction into neural signals. In subsequent chapters we’ll learn how those signals are transmitted to the brain and translated into the experience of perception.
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2.   Light, on its way to becoming a sensation (a visual sensation, that is), can be absorbed, scattered, reflected, transmitted, or refracted. It can become a sensation only when it’s absorbed by a photoreceptor in the retina.

3.   Vision begins in the retina, when light is absorbed by rods or . The retina is like a minicomputer that transduces light energy into neural energy.
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4.   The retina sends information to the brain via ganglion cells, neurons whose ----- axons dendrites make up the optic nerves. Retinal ganglion cells have surround receptive fields and are concerned with changes in contrast (the difference in intensity between adjacent bits of the scene).
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5.   The visual system deals with large variations in overall light intensity by (a) ----- limiting maximizing regulating the amount of light entering the eyeball, (b) using different types of ----- ganglion cells photoreceptors in different situations, and (c) effectively throwing away photons we don’t need.
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6.   Age-related macular degeneration (AMD) is a disease associated with aging that affects the macula. The leading cause of visual loss among the elderly in the United States, AMD gradually destroys sharp ----- central peripheral vision, making it difficult to read, drive, and recognize faces.
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7.   Retinitis pigmentosa (RP) is a family of hereditary diseases characterized by the progressive death of photoreceptors and degeneration of the pigment epithelium. In the most common form of the disease, patients first notice vision problems in their ----- central peripheral vision and under low-light conditions—situations in which rods play the dominant role in collecting light.
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8.   A number of exciting new developments are aimed at restoring sight in individuals with blinding retinal disease.