key concept 45.4 Photoreceptors Respond to Light

Sensitivity to light—photosensitivity—confers on the simplest animals the ability to orient to the sun and sky, and it gives more complex animals rapid and extremely detailed information about objects in their environment. Photosensitivity is ubiquitous in the animal kingdom, and the molecular basis for that sensitivity is a family of visual pigments that have been evolutionarily conserved.

973

focus your learning

  • Rhodopsin transduces light energy into changes in membrane potential.

  • Vertebrate rods are sensitive to light with high sensitivity; cones are sensitive to color.

  • Receptive fields of photoreceptors send their output to ganglion cells along with lateral processing by horizontal and amacrine cells, enabling motion and contrast detection.

In this section you will learn about the structures of eyes, the organs that gather light energy and focus it onto photoreceptor cells. Then you will learn how visual pigment molecules of photoreceptors respond when stimulated by light energy and the molecular mechanism that transforms that light energy into action potentials. You will also learn about color vision and how photoreceptor information is processed in the neural layers of the vertebrate eye.

Animation 45.2 Photosensitivity

www.life11e.com/a45.2