Central visual processing Flashcards
How we see colour?
The cone is made up of three different types of receptors that allow you to see colour.
These three different receptors are aptly named the short, medium, and long-wavelength cones. This size difference represents each receptor’s sensitivity to light.
Difference between cones and rod
The most important difference between the cone and the rod is that the cone is more light-sensitive than the rod, and the cone requires much more light to enter it in order to send signals to the brain.
What is calciums tole in light adaptation?
Increases the synthesis of cGMP
Cone signal circuitry
Cone photoreceptors-Horizontal cells-bipolar cells-ganglion cells
In the cone glutamate is passed through the synapse through mGlluR6 receptor onto the On centre bipolar cell(constant depolarisation occurs), then glutamate is released into the on centre ganglion cell
The cone also passes glutamate to the AMPA kinase receptor into the off centre bipolar cell(hyper polarisation occurs) and glutamate is then released into the off centre ganglion cell
Rod signal circuitry
Rod photoreceptor- Rod bipolar-All amacrine cells-on and off ganglion
What are on and off retinal ganglion
There are on and off retinal ganglion
They are able to tell us where light shines and when it stops
Stimulation of different regions of the receptive field
What happens to light on centre?
Reduces glutamate release on the on centre cell and less inhibition occurs on TRP channel
Maximum response occurs
What happens to light off centre?
Light gives maximal response when hitting the off centre
Outside the off centre gives below baseline response
Entirely outside the off centre gives baseline response
What are Horizontal cells?
They are GABAergic
Light onto only centre field causes hyper polarisation and reduce glutamate to give a big response
Light onto centre and more releases less GABA onto cone
