Difference between Rods & Cones is all except: (AIIMS May 2009)
Rods and cones are the photoreceptors that transform light energy into nerve impulse (Option C).
1. There are about 120 million rods and 6.5 million cones( RODS:CONES= 20:1)(Option B)
2. The highest density of cones is at the fovea.
3. Rods are absent at the fovea
4. Cones are primarily responsible for the photopic vision and the colour vision. (Option D)
5. Rods are primarily responsible for scotopic (Low illumination ) vision and peripheral vision.
6. Cones are of three types with different type of pigments and each cone pigment responds to specific wavelength of light, giving rise to colour vision. (OPTION D). The differences are present in the opsin portion of the molecule, whereas the chromophore11- cis- retinal remains the same.
7. The peak absorbance wavelength of the blue, green and red sensitive cones lie at about 435, 535 and 580 nm respectively.
8. The peak absorbance wavelength of rods lies within 493-505 nm .
9. The cone receptor potential has a sharp onset and offset, whereas the rod receptor potential has a sharp onset and a slow offset.
10.The rod responses are proportionate to the stimulus intensity at low levels of illumination, whereas the cone responses are proportionate to stimulus intensity at high levels of illumination when the rod responses are maximal and cannot change. (Option A)
11.The cones generate good response to changes in light intensity but do not represent absolute illumination well, whereas rods detect absolute illumination. (Option A)