Retinal Organization Flashcards
What is the first neuronal layer encountered by light?
The retinal ganglion cells (ganglion cell layer)
What is the inner plexiform layer comprised of?
Synaptic zone containing contacts between bipolar cells, amacrine cells and retinal ganglion cells
What is the inner nuclear layer comprised of?
Cell bodies of amacrine, bipolar, and horizontal cells
What is the outer plexiform layer comprised of?
Synaptic zone containing contacts between bipolar cells, horizontal cells, and photoreceptors
What is the outer nuclear layer comprised of?
Cell bodies of photoreceptors
What are the functions of the pigmented epithelium?
Absorbs any light that passes all the way through the retina - preventing acuity reduction
Turnover of photopigments and photoreceptor disks
What is the vertical pathway?
A three neuron chain including photoreceptors, bipolar cells and retinal ganglion cells
What neurotransmitter is released by all cells within the vertical pathway?
Glutamate
*however the post-synaptic response can be excitatory or inhibitory
Which cell is the only cell that fires action potentials within the vertical pathway?
Retinal ganglion cells
Photoreceptors and bipolar cells fire graded potentials only - neurotransmitter release is proportional to membrane depolarization
What types of cells form the lateral pathway?
Horizontal and Amacrine cells
What is the function of horizontal cells?
Mediate lateral inhibition between photoreceptors
Release GABA
What is the function of amacrine cells?
Multiple functions
Release many neurotransmitters depending on type of cell
Why is the peripheral retina more sensitive to low light levels than the fovea?
Higher ratio of rods to cones
Why is the fovea better at resolving fine detail?
It has a low receptor to ganglion (output) cell ration
What results from the pit-like shape of the fovea?
Enhanced visual acuity due to the reduced scattering of light
