Sensory Receptor Cells of the Eye

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Sensory Receptor Cells of the Eye

• Sensory Neural Systems
• 22 January 2008
• Rachel L. Leon

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Eye Anatomy
http//www.matossianeye.com/art2/ANATONY2.jpg
http//www.deltagen.com/target/histologyatlas/atla
s_files/sense/eye_retina_40X.jpg
http//scienceblogs.com/clock/2006/06/bio101_lectu
re_6_physiology_re.php
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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
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Photoreceptors Rod Cells
http//cas.bellarmine.edu/tietjen/images/Eyes!.htm
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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

http//www.nature.com/nature/journal/v427/n6969/fi
g_tab/427020a_F1.html
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Photoreceptors Cone Cells

• Three pigments
• Max sensitivity 420nm, S pigment
• Max sensitivity 530nm, M 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

http//www.giangrandi.ch/optics/spectrum/visible-a
.jpg
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Retinal Processing

• Simple version photoreceptor ? bipolar cells ?
  ganglion cells
• Ganglion cells are the first cells that produce
  an action potential
• Cone pathway
• Cones receive input from rods
• Two subsets of bipolar cells ON and OFF cells
• Rod pathway
• Bipolar cells are sign inverting, connect to
  amacrine cells
• Amacrine cells ? ganglion cells, cone bipolar
  cells

http//www.mitre.org/news/the_edge/september_99/se
p99_imgs/retina.jpg