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The mammalian eye PowerPoint Presentation
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The mammalian eye

The mammalian eye

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The mammalian eye

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  1. The mammalian eye By SzeNga CHAN Cecilia

  2. Content • Structure and function of eye • Properties in focusing an image • Features of retina • Structure of rod cells and cone cells • Role of rod cells and cone cells • Sensitivity of vision • Acuity of vision • Effect on rhodopsin

  3. Features and Functions • Layers • Sclera-tough layer-form the transparent cornea -transparent conjunctiva covers the cornea-transmission-Refraction • Choroid-rich in blood vessels-black in color-prevent internal reflection of light • Retina-photoreceptive-contains rod cells and cone cells

  4. Features and Functions • Aqueous humour-behind the cornea-a clear salt solution • Vitreous humour-behind the lens-jelly-like dark solution • Fovea- contains most of the rod cells and cone cells- light rays are focused onto it • Blind spot-the connection point of optic nerve-no rod cells or cone cells can be found

  5. How to adjust the amount of light goes into the eye? • Strong light-circular muscle contracts-radial muscle relaxes-pupil becomes smaller -less light rays enter the eye Iris is a muscular diaphragm surrounding the pupil

  6. How to adjust the amount of light goes into the eye? • Weak light-circular muscle relaxes-radial muscle contracts-pupil becomes dilate- more light rays enter the eye http://www.youtube.com/watch?v=JadaWSDxBYk&feature=related

  7. How to adjust the focus point? • A near target-ciliary muscles contract-suspensory ligament slack-lens more rounded shape(more convex)-light focused on retina

  8. How to adjust the focus point? • A far target-ciliary muscles relax-pull the suspensory ligament taut-lens flat (pull in)- light focused on retina

  9. Features of retina Three main layers Photoreceptorrod cells and cone cells Bipolar neurones Sensory neurones

  10. Rod cells and Cone cells

  11. Effect on rhodopsin • Light energy is absorbed by retinal • Rhodpsin separate to retinal and opsin • Opsin causes the closure of Na channel • Less inhibitory neurotransmitter is released • Less inhibition of bipolar neurons • Depolarisation • Action potential • Optic nerve

  12. Reformation of rhodopsin • Catalyst • ATP • Trans-retinal + opsin rhodopsin • In iodopsin in cone cells, the same reaction happen • but it breaks less easily and reforms more slowly

  13. Exam question The diagram shows the distribution of rods and cones in the retina of a human eye. Using information in the diagram, explain how: (i) rod cells enable us to see in conditions of low light intensity; Several rod cells to each neuron / bipolar cell/each synapse/convergenceprinciple of additive effect of light striking several rod cells/(spatial)summation; (ii) cone cells enable us to distinguish between objects close together. Each cone connects to a single neurone/no convergence;brain receiving information from each cone cell individually

  14. Reference • http://www.virtualmedicalcentre.com/uploads/VMC/DiseaseImages/2133_eye_anatomy_label_v2_700.jpg • http://upload.wikimedia.org/wikipedia/commons/2/2e/Mona_Lisa_detail_eyes.jpg • http://thebrain.mcgill.ca/flash/d/d_02/d_02_m/d_02_m_vis/d_02_m_vis_1a.jpg • http://www.sapdesignguild.org/editions/edition9/images/accomodation.png • http://www.insightseyecare.net/EyeEducation/retinaNeuronalLayers.jpg • http://cas.bellarmine.edu/tietjen/Laboratories/Eye07.gif • http://4.bp.blogspot.com/_GrFZK0cwrtk/SCXHEojGp5I/AAAAAAAAAB8/7y0hnATxxFg/s400/6a00d41423ae593c7f00d41422a3576a47-320pi.jpg • http://images.ifguk.co.uk/products/609/609-large1.jpg • All information obtained in the internet on 18th April,2010

  15. ???

  16. Good luck in EXAM! 