ACROSS
2. retinal region where cone cells are most concentrated.
4. adjustable opening that allows light into a camera eye.
8. sensory receptor that responds to pressure, position, or acceleration.
10. cell photoreceptor that is active in dim light; provides coarse perception of image and detects motion.
11. pain-relieving chemical made by the body.
13. disk-shaped structure that bends light rays so they fall on an eye’s photoreceptors.
17. sensory receptor that responds to light.

DOWN
1. sensory receptor that responds to a chemical.
3. detection of light in a way that provides a mental image of objects in the environment.
4. the meaning a brain derives from a sensation.
5. temperature-sensitive sensory receptor.
6. coiled, fluid-filled structure in the inner ear that holds the mechanoreceptors involved in hearing.
7. clear, protective covering at the front of a vertebrate eye; helps focus light on the retina.
9. detection of a stimulus.
12. perception of tissue injury.
14. chemical that is released by one individual and affects another member of the same species.
15. photoreceptor-containing layer of tissue in an eye.
16. circular muscle that adjusts the shape of the pupil to regulate how much light enters the eye.