Transduction Flashcards
Define Phototransduction
The conversion of light energy to an electrochemical response by photoreceptors
What from the electromagnetic spectrum stimulates retina
Only visible light
Where exactly does the energy from light waves stimulate
The Photoreceptors on the retina
What is photoreceptors composed of
Rods and cones
Where is the photoreceptors found on the modified neurons
The outer segment containing stacks (rods) or discs (cone) of membrane bound lamellae
What is the transmembrane helical protein found in the lamellae called
Rhodopsin pigment
What is the rhodopsin pigment composed of
Ospin with a vitamin A compound called 11cis retinal nesting inside
Why is there three different types of opsin (S,M,L)
As different pigments respond to different wavelengths of light
What happens when photon of light hits the retina
When light hits the retina causes a chemical change in the formation of 11cis retina (bendy) to isomer all trans retina (straight)
The all trans retinal cannot fit inside the opsin so causes the rhodopsin pigment to split
What affect does the odopsin remaining in the cell membrane after the rhosposin splits have
Results in the bleaching of the visual purple (rhodopsin) as the odopsin left behind gives a bleached appearance
What does activated Rhodopsin aka odopsin therefore stimulate
Phototransuction cascade
How does the phototranduction cascade generate an action potential
Rods and cones are depolarised so opsin triggers the closing of sodium channel transmitting hyperpolorisation signal (Ca+ ions) which reaches bipolar cell and generates an AP activating the optic nerve
Where does visual regeneration occur
Happens at the retinal pigment epithelial cell (10th retina layer)
What occurs in visual pigment regeneration
Transform all trans retina back to 11cis retina so can fit back inside odopsin and form rhodopsin again
What is the problem in visual pigment regeneration
Very easily for compounds to become esters therfore loose vitamin A compound
