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Published byClare Mills Modified over 9 years ago
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Vision 1
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Structure of the eye
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Light passes through ganglion and bipolar cells, without distortion, to visual receptors –bipolar cells receive input from visual receptors –ganglion cells receive input from bipolar cells –amacrine cells exchange information with bipolar cells and send information to ganglion and other amacrine cells provides many options for complex processing of information Optic nerve is made up of axons of ganglion cells –the point where optic nerve leaves the eye does not have receptors and is our blind spot
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Phototransduction Photopigments in outer segment Stimulated by light ( bleaching ) Activates G-proteins ( transducin ) In turn activates effector enzyme ( phosphodiesterase, PDE ) Decreases cytoplasmic concentration of 2 nd messenger molecule ( cyclic GMP ) Ion (sodium) channel in membrane closes Membrane potential: hyperpolarizes
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Centre of the eye: fovea Surround: parafovea In the fovea different distribution of photoreceptors than in the parafovea ( in fovea more cones than rods )
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(CFF: critical flicker fusion: do you notice on/off-switching?)
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Colour vision: 3 types of cones
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