Image formation & processing Flashcards
What are the two layers of the retina?
Neurosensory retina - inner layer.
Retinal pigment epithelium - outer layer.
What does the outer limiting membrane contain?
Muller cells - glial cells that support neurones.
What does the outer plexiform layer contain?
Synapses of photoreceptor cells & bipolar cells.
What does the inner nuclear layer contain?
Cell bodies of bipolar cells.
What does the inner plexiform layer contain?
Synapses of bipolar cells & ganglion cells.
What does the ganglion cell layer contain?
Cell bodies of ganglion cells.
What does the nerve fibre layer contain?
Axons of ganglion cells - form the optic nerve.
What does the inner limiting membrane contain?
Terminals of muller cells.
Also forms the basement membrane.
What is the choroid & what does it contain?
Vascular layer of the eye between the sclera & retina.
Contains the choricocapillaris - blood supply to the outer retina.
What happens to photoreceptor cells in the dark?
They are “turned on”.
No photons are absorbed by rhodopsin > cGMP can activate cGMP-gated Na+ channels > depolarisation > release of glycine onto bipolar cells > inhibition of bipolar cells.
What happens to photoreceptor cells in the light?
They are “turned off”.
Photons are absorbed by rhodopsin > transformation from 11-cis to 11-trans retinal > activation of opsin > activation of transducin > activation of PDE > PDE converts cGMP into GMP > inactivation of cGMP-gated Na+ channels > hyperpolarisation > activation of bipolar cells > activation of ganglion cells > neural transduction to the visual cortex.
What are the highest concentration of cone cells found & why?
In the fovea.
Allows for high acuity central vision.
What pigments sense colour?
Opsins.
What does a deficiency in opsin production result in?
Dischromotopsia.
What is red colour weakness known as?
Protanopia.
What is green colour weakness known as?
Deuteranopia.
What is blue colour weakness known as?
Tritanopia.
What are the most common colour vision disorders?
Red-green deficiencies.
What hormone is thought to have a role in pain & visual disturbances during migraines?
Melatonin.
