10&11_biology of seeing '09

10&11_biology of seeing '09 - 1 The Biology of...

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Unformatted text preview: 1 The Biology of Seeing The Biology of Seeing Recent article in Nature : color blindness in monkeys cured by gene therapy! How sensory stimuli elicit behavior How sensory stimuli elicit behavior Information, in the form of energy , is detected by sensory receptor cells. transmitted by sensory neurons to nervous system. integrated by nervous system which activates muscles. sequence modified by hormones Energy can be: light sound Corresponding sense: Corresponding sense: seeing seeing hearing hearing Animal Senses mechanical chemical magnetic electrical touch & proprioception touch & proprioception smell & taste smell & taste magnetoreception magnetoreception electroreception electroreception Seeing, or Vision Seeing, or Vision Vision commonly involves assessment of: A. presence and intensity of light B. color and other properties C. images D. distance, location and motion of objects A. Detecting light A. Detecting light Light is electromagnetic radiation . Light has properties of particles, called photons photons . Detecting light = detecting photons 2 Rhodopsin is a protein complex consisting of two subunits, opsin opsin and retinal* retinal* . Opsin Detecting photons requires the photopigment molecule rhodopsin rhodopsin . Retinal * Genes code for these subunits! When retinal retinal absorbs a photon, it changes shape. Light cis form trans form Opsin Retinal Rhodopsin Change in shape activates leads to the closing of closing of Na+ channels Na+ channels and a change in membranes electric change in membranes electric potential potential. Important! Important! All sensory detection involves conversion of some kind of energy into bioelectrical energy bioelectrical energy . B. Seeing in Color B. Seeing in Color Color provides information that brightness alone does not. Some Uses of Color in Animals courtship signals warning coloration nectar foraging 3 What is Color? What is Color? Radio Microwaves Infrared Short s Ultraviolet Gamma Long s Light also has properties of waves Color relates to wavelength ( wavelength ( ) ) (for humans) Wavelength sensitivity of rhodopsin depends on amino acid composition of amino acid composition of opsin* opsin* . Opsin Retinal Rhodopsin *Different genes code for different opsins. 1.0 0 8 L opsin 560 M opsin 530 S opsin 420 Visible spectrum Human color vision involves 3 opsins. Relative proportion of light absorbed 0.8 0.6 0.4 0.2 0.0 400 500 Wavelength (nm) 600 1. Dichromatic vision 2 pigments-- many insects, most mammals, incl. dogs 2 Trichromatic vision 3 pigments Dogs are not really colorblind!...
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This note was uploaded on 12/09/2009 for the course ECOL 487R taught by Professor Papaj during the Spring '09 term at University of Arizona- Tucson.

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10&11_biology of seeing '09 - 1 The Biology of...

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