The Problem of Visual Excitation*

摘要: This paper attempts to come grips with the problem, how action of light on a visual pigment results in nervous excitation. The only vision is isomerize retinene, chromophore pigments, from 11-cis all-trans configuration. change triggers progressive opening-up protein structure, exposing new reactive groups. Since absorption one photon by molecule may stimulate dark-adapted rod, some large amplification process needed between act and response. be an enzymatic catalysis, or consequence puncturing critical membrane. A microspectrophotometric study retinas single rods shows outer segment have quasi-crystalline which pigments are almost perfectly oriented, even “free” molecules capable diffusion maintain degree orientation. Examination mud puppy electron microscope has revealed several aspects structure: (1) system cytoplasmic filaments (“dendrites”) springing inner segments cones standing like palisades around segments. These facilitate exchanges material (2) Systems particles membranes dendrites epithelium processes, involved interchanges (3) crystalline array rod lamellae, contain pigment. If so, measurements situ show that each particle should about 50 Such typically solid-state processes as exciton migration photoconduction probably at most very limited scope cones. seat excitation plasma membrane envelops composes also lamellae