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The Visual System Part 1 Aqueous humor secreted from Ciliary body, Flos to Anterior Chamber, drains through Canal of Schlemm _________ Intrinsic Muscles of the Eye: The Iris • Iris – circular.....________ – radial.....…________ • Dilating pupil for eye exam: how to do it? Pharmacology of pupillary dilation: _________ Intrinsic Muscles of the Eye: Ciliary Muscle • Ciliary muscle relaxed = tension on zonular fibers = tension on lens = flattened lens = _________________ • Ciliary muscle contracted = tension on zonular fibers reduced = less tension on lens = lens becomes more spherical =__________________ • Eye strain Using a Microscope or Binoculars Near point of Accomodation 0.06 0.07 0.08 0.09 0.12 0.14 0.16 0.18 0.3 0.4 With Convergence Demonstrate Convergence Extraocular muscles Motor innervation by CN III = __________ CN IV = __________ CN VI = __________ __________= misalignment of eyes Due to _______________________ Lateral geniculate nucleus a subdivision of the thalamus. Visual reflexes: ___________, ___________, ___________, ___________. Clinical Case Study: Hyperprolactinemia, p. 627-8 of text The Visual System Part 2 The Retina What do you notice with regards to the connections in this complex circuit? What cells seem to have axons? What does this mean with regards to sensory coding? S 15 Receptors for light detection Photoreceptor cells 4 light sensitive proteins: - 1 type of _____ - 3 types of ______, each with a single type More membrane = more photosensitive molecules = more sensitive to light Visual Acuity • 120,000,000 rods and 6,000,000 cones per retina • 1,200,000 retinal ganglion cells & axons • ____:___convergence ratio • Fovea: •Differences in spectral sensitivity due to 4 types of ______. Web-based color deficiency test _______ Theory of Color Vision “Bleaching” of photopigments _________ _________ The cascade of events initiated by light in a photoreceptor. The result of the cascade is to close a cGMP-gated sodium channel, reducing the inward current and hyperpolarizing the membrane. Source: Kandel, Schwartz & Jessell, Principles of Neural Science, 4th Edn What is the advantage of this multistep process? Hubel and Weisel Experiments Lateral Geniculate Neurons Youtube Retinal Ganglion Cells Visual Cortex Neurons _____________in the Cortex • Motion sensitive • Color and shape sensitive
