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Vision

Vision. Eye . 70% of all sensory receptors are in the eye To interpret visual stimuli we must collect and focus light onto photoreceptors Eye is protected by bony orbit & cushion of fat Accessories: eyebrows, eyelids, conjunctiva, lacrimal apparatus (tears) & eye muscles. Eye structures.

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Vision

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  1. Vision

  2. Eye • 70% of all sensory receptors are in the eye • To interpret visual stimuli we must collect and focus light onto photoreceptors • Eye is protected by bony orbit & cushion of fat • Accessories: eyebrows, eyelids, conjunctiva, lacrimal apparatus (tears) & eye muscles

  3. Eye structures • Sclera - white of the eye • Conjunctiva – 2: eyelid & whites • Cornea - bends light • Aqueous humor - nourishes, cushions cornea/lens • Pupil - adjustable opening of Iris • Lens – regulates focus • Vitreous humor - transmits light to retina • Retina – absorbs light converts to impulses • Optic nerve – impulses to brain • Optic disk – blind spot-nerves exits eye

  4. Figure 12.14

  5. Sight • Light passes through the clear cornea, the pupil, the lens and the aqueous fluid before striking the photoreceptors in the retina • Quarter-billion photoreceptors! • Rods – dim light, black & white, peripheral • Cones – bright light, color • Cones are lateral to blind spot & concentrated in minute pit: fovea centralis

  6. Photopigment in flattened discs proteins change shape when exposed to light energy • Some Na+ channels close limiting the release of neurotransmitters that inhibits bipolar cells • Light increases activity of bipolar cells  activates ganglion cells • Light stimulus is converted into action potentials in retina

  7. Figure 11.2

  8. Pigment rhodopsin found in the retina (bovine studies) is also found in certain green algae (dinoflagellate)! Pigment is concentrated in the eyespot of the algae and under light conditions it may become mobile But wait! There’s more!

  9. Salinibacter ruber - extreme conditions from saltern crystallizer ponds in Alicante and Mallorca, Spain. Technology possibilities: salt metabolism in anaerobic conditions and in presence of light can switch to photosynthesis with rhodopsin (binary code  new computer technology possibility at speed of light!) Tech possibility

  10. http://www.nytimes.com/1985/01/08/science/the-eyes-of-algae-offer-a-view-of-man.html?sec=health&spon=http://www.nytimes.com/1985/01/08/science/the-eyes-of-algae-offer-a-view-of-man.html?sec=health&spon= http://www.bio-medicine.org/biology-news/A-salty-tale-3A-New-bacterial-genome-sequenced-from-ancient-salterns-2144-1/ References on rhodopsin

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