Flashcards in Physiology of vision Deck (19)
Describe the pathway of light in the retina in terms of the cellular layers?
Describe the direction of signal in the retina in terms of cellular layers
In what light conditions will the glutamate release be at its highest?
What does light do to rhodopsin?
Converts 11-cis -retinal to all-trans retinal
Will light open or close sodium channels?
Will light increase or decrease cGMP levels within the retina?
Do rods show high or low convergence?
High (and therefore cones show low)
What is the impact of a higher convergence in the rod system?
Increased sensitivity whilst decreasing acuity
Describe the 3 different cones and the light they process
Short wave = blue
Medium wave = green
Long wave = red
Describe the OFF pathway in the retina
Dark = more glutamate
Ionotropic receptors on bipolar cells
Membrane is more positive
Ganglion cell is more positive; action potential
Describe the ON pathway in the retina
Light; less glutamate
Metabotropic receptors on bipolar cells resulting in decreased calcium and increased potassium
Membrane more positive
Ganglion cell more positive; action potential
What is the function of lateral inhibition?
Exaggerates the difference in stimulus intensity detected by adjacent neurones
Aids with localization
What neurotransmitter will horizontal cells release?
What is the center surround organisation in the retina?
Ganglion cells have an either an ON centre and OFF surround or OFF centre and ON surround
What is the purpose of the center surround organization?
Emphasize areas of contrast; i.e. it sharpens the boundary between objects of different luminance
What are the different types of retinal ganglion cells?
M - movement
P - form and colour
Which fibres from the eyes will decussate?
Nasal fibres at the optic chiasm
Which layer of the primary visual cortex is vision processed?