FNS 34 Photoreceptors and Color Vision

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Author:
zf2010
ID:
72598
Filename:
FNS 34 Photoreceptors and Color Vision
Updated:
2011-03-13 16:01:32
Tags:
USUHS Photoreceptors Color Vision
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FNS 34 Photoreceptors and Color Vision
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  1. 1. Which type of photoreceptors retect low light levels?
    2. Color, acuity?
    • 1. Rods
    • 2. Cones
  2. Rods:
    1. Photopigment
    2. Location
    3. Convergence
    • 1. Rhodopsin
    • 2. Peripheral to fovea
    • 3. Highly convergent
  3. Cones:
    1. Photopigment
    2. Location
    3. Convergence
    • 1. 3 Cone opsins
    • 2. Fovea
    • 3. Less convergent
  4. What are the receptors activated in the following levels of illumination?
    1. photopic?
    2. mesopic?
    3. scotopic?
    • 1. Cones
    • 2. Rods and Cones
    • 3. Rods
  5. How do photoreceptors respond to light?
    • Change in photopigment molecule
    • Hydrolysis of cGMP --> closes cGMP-gated Na channels
    • Membrance hyperpolerizes from 30 mV
    • Decreases amount of inhibitory neurotransmitter released to bipolar cell
  6. What are the targets of the ganglion cell axons?
    • Lateral geniculate body
    • Superior colliculus
    • Pretectal Olivary Nucleus
  7. What cell types modulate photoreceptor interactions with bipolar cells?
    Horizontal Cells
  8. What is the pathway and function of the off-surround response?
    • Pathway: photoreceptors hyperpolarize adjacent horizontal cells, which depolarize the on-center receptor (bipolar cell hyperpolarizes)
    • Responsible for sharpening boundaries between light and dark
  9. If both on-center and off-surround photoreceptors are stimulated, what will be the resulting ganglion cell firing rate?
    No change from basal firing rate
  10. What wavelengths are the following cones most sensitive to:
    1. blue?
    2. green?
    3. red?
    • 1. 419 nm
    • 2. 531 nm
    • 3. 559 nm
  11. Which type of cones are most sensitive to light? Least sensitive to light?
    • Most sensitive - red cones
    • Least sensitive - blue cones
  12. 1. Which cones are found in the central region of the fovea?
    2. Why is one left out?
    • 1. Red and green cones
    • 2. Blue cones are left out because of chromatic aberration (blue refracts through lens at too great an angle, so image would be blurry)
  13. When a single type of cone is missing or non-functional, what is the result?
    • Red-green color blindness
    • X-linked recessive

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