1. 1 Psychology 304: Brain and Behaviour Lecture 32

2. 2 Course evaluations will be available online until December 4 th. If you have not received an e-mail regarding evaluations, visit: https://eval.olt.ubc.ca/arts. Your feedback is extremely valuable—both to the Psychology Department and to me. I modify courses and provide feedback to TAs on the basis of student feedback. Please complete your evaluations for this course. Your evaluations will be secure and anonymous. 2 Reminder

3. 3 From last class ….

4. 4 Olfactory Receptors and Pathways of the Olfactory System 4 Olfactory Epithelium

5. 5 1. What is the structure of the eye and where are the receptors for light? (continued) The Visual System

6. 6 By the end of today’s class, you should be able to: 1. distinguish between cones and rods. 3. explain how an action potential is generated in the retinal cells of the visual system. 2. describe duplex retinal theory.

7. 7 What is the structure of the eye and where are the receptors for light? (continued)

8. 8 The Cellular Structure of the Retina

9. 9 A Section of the Retina Front of Eye, Pupil, Vitreous Humor

10. 10 A Section of the Retina and Optic Nerve Front of Eye, Pupil, Vitreous Humor

11. 11 There are two types of receptors in the human retina: cones and rods.

12. 12 Cones are associated with relatively high visual acuity because a single ganglion cell receives input from only one or a few cones (low convergence). Rods are associated with relatively high sensitivity to illumination because a single ganglion cell receives input from many rods (high convergence).

13. 13 Convergence of Cones and Rods on Retinal Ganglion Cells

14. 14 The fovea is specialized for high-acuity vision. Visual acuity at the fovea is enhanced by: 1. the presence of cones. 2. the “thinning” of the bipolar and ganglion cell layers in this region.

15. 15 The Fovea

16. 16 Retinal Cells at the Fovea

17. 17 Cone vs. Rod Density at the Fovea Nasal Half of Retina

18. 18 When light reaches a receptor, photopigments (e.g., rhodopsin) are activated that hyperpolarize the receptor cell. Reduced neurotransmission by the receptor cell results in depolarization of the adjacent bipolar cell (see Figure 10.13 on p. 295 of textbook, left side ONLY, “on-center” cells).

19. 19 In turn, depolarization of the bipolar cell results in depolarization of the adjacent ganglion cell. When the ganglion cell is stimulated, an action potential is triggered that passes down the cell’s axon, along the optic nerve—cranial nerve II.

20. 20 Generation of an Action Potential in the Retina

21. 21 1. What is the structure of the eye and where are the receptors for light? (continued) The Visual System