TABLE 4.

Additional list of symbols and definitions pertaining to the second biophysical function

Symbol	Definition
Φa, Φaz	Absorbed flux in one layer at the base and at depth z
Jn	Surface density of pigment (molecules μm−2); Jn = n/At
δ	In situ path length in visual cells corresponding to a single pigment-laden lipid bilayer (lamella); δ = 15 nm is taken as its equivalent thickness
At	Total lamellar surface area of an outer segment
c	Concentration of visual pigment; c = n/Atδ = Jn/δ
n	Total number of visual pigment molecules contained in an outer segment
no, nz	Number of visual pigment molecules in a lamella at the base and at z
pz	Probability of absorption of a quantum by a single layer at z
γ	Quantum efficiency of bleaching; number of photons absorbed per number of photoactivations that result in bleaching
Sz	Signal from light activation (ionic current) at level z
Nz	Noise produced in the dark at level z (ionic current)