RETINAL TRANSDUCTION:  ROD and CONE FUNCTION

B. Rod and Cone Function

1. General characteristics of rods and cones

Rods Cones 120,000,000 per eye 6,000,000 per eye Uniformly distributed throughout retina, except not found in fovea Mainly confined to fovea High light sensitivity (function at low light levels) (==>) Lower sensitivity (function limited to higher light levels) Night vision (scotopic) Daytime vision (photopic ) Lower acuity, due in part to great convergence of neurons innervating rods along visual pathway Higher acuity, due in part to minimal convergence Visual pigment is rhodopsin Three separate visual pigments Monochromatic vision Color vision

Note: Absorption of light photons by the rod and cone pigments is the first step in the transduction process