Lecture 4 - Sensory Mechanisms-Updated

Photoreceptors vision some animals focus the light of

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Unformatted text preview: ac6on poten6al •  Bipolar cells do not fire ac6on poten6al but change the release of neurotransmiiers sent to ganglion cells upon input •  Ganglion cells transmit ac6on poten6al through the op6c nerve to the visual cortex (part of the brain that process images) 37 Photoreceptors  ­ Vision 38 Photoreceptors  ­ Vision 39 Photoreceptors  ­ Vision •  Eyecup –  Direc6on and intensity of light (or absence of light) –  Does not form visual images –  In flatworms, two eye cups gives sense of orienta6on 40 Photoreceptors  ­ Vision •  Compound eye (Arthropods) –  Individual light ­focusing elements called omma9dia –  light is focused through a lens onto a central region formed from mul6ple overlapping photoreceptors –  mosaic image –  extremely good at detec6ng mo6on and rapid flashes of light, not great resolu6on –  many insects can perceive ultraviolet light 41 Photoreceptors  ­ Vision •  Single ­lens eye –  Found in vertebrates, some mollusks and some snails –  Sclera: strong outer white sheath –  Cornea: con6nuous with sclera but thin and transparent –  The contrac6on or relaxa6on of ciliary muscles aiach between the sclera and lens adjusts the shape of the lens to focus light images 42 Photoreceptors  ­...
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