1. Sensory Receptor Cells of the Eye Sensory Neural Systems 22 January 2008 Rachel L. Leon

2. Eye Anatomy http://www.matossianeye.com/art2/ANATONY2.jpg http://www.deltagen.com/target/histologyatlas/atlas_files/sense/eye_retina_40X.jpg http://scienceblogs.com/clock/2006/06/bio101_lecture_6 _physiology_re.php

3. Sensory Receptors of the Eye Photopigment found in the modified cilia which contain disc membranes Rods have rhodopsin, allow for scotopic vision Cones have three types of photopigments, allow for photopic vision http://cas.bellarmine.edu/tietjen/images/Eyes!.htm

4. Photoreceptors: Rod Cells http://cas.bellarmine.edu/tietjen/images/Eyes!.htm

5. Phototransduction in Rod Cells RGS9 bound to R9AP turns off response to light by increasing rate of GTP hydrolysis by transducin Mutations in RGS9 or R9AP cause slow deactivation cause difficulty in adjusting to changes in light levels, as well as in seeing low-contrast, moving objects cause difficulty in adjusting to changes in light levels, as well as in seeing low-contrast, moving objects http://www.nature.com/nature/journal/v427/n6969/fig_tab/427020a_F1.html

6. Three pigments Max sensitivity 420nm, S pigment Max sensitivity 420nm, S pigment Max sensitivity 530nm, M pigment Max sensitivity 530nm, M pigment Max sensitivity 560nm, L pigment Max sensitivity 560nm, L pigment Each cone only has one type of pigment Receptive fields overlap, so the strength of response from each of the responding cone types allows identification of the wavelength Photoreceptors: Cone Cells http://www.giangrandi.ch/o ptics/spectrum/visible- a.jpg

7. Retinal Processing Simple version: photoreceptor  bipolar cells  ganglion cells Ganglion cells are the first cells that produce an action potential Ganglion cells are the first cells that produce an action potential Cone pathway Cones receive input from rods Cones receive input from rods Two subsets of bipolar cells: ON and OFF cells Two subsets of bipolar cells: ON and OFF cells Rod pathway Bipolar cells are sign inverting, connect to amacrine cells Bipolar cells are sign inverting, connect to amacrine cells Amacrine cells  ganglion cells, cone bipolar cells Amacrine cells  ganglion cells, cone bipolar cells http://www.mitre.org/news/the_edge/september_99/sep99_imgs/retina.jpg