Lecture 6 1-23-08

Lecture 6 1-23-08 - i. Photoreceptors are at the very back;...

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I. Sensory Informators e.g. Taste pp 1055-1056 Figure 49.14 Also, Mechano receptors : p 1048 II. Mammalian Eye a. Anatomy Figure 49.18, 49.19 b. Light Transduction (Figure 49.20) i. Cell Types: Photoreceptors 1. rods: detect black/white; way more sensitive than cones, hence we see in black and white in the dark; if you are nocturnal you can detect a single rod firing a. Photo pigment in the outer segments contains rodopsin i. Which is made of two parts a protein opsin and retinal which is from vitamin D. Retinal absorbs the light 2. cones: detect color ii. Molecular Mechanism In the dark: cGMP some Na+ channels open increasing the Vm (= “dark current”) iii. Picture 1 (Figure 40.21 and 22) III. Visual System Pathway Retina Lateral Geniculate Visual Cortex a. Retina: 5 cells layers at the back of the eye (Figure 49.23 and 24)
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Unformatted text preview: i. Photoreceptors are at the very back; project to the bipolar cells who protect to retinal ganglian cells (RGCs) which protects to the brain by sending their axons out in a bundle which make up the optic nerve. ii. We also have a layer of horizontal cells which get input from the photoreceptors and then put out to the bipolar cells iii. The Amacrine cells get input from the bipolar cells and put out to the RGCs IV. Concept of Receptive Fields (RFs) Concept: RF is defined as that part of the sensory field that impinges or effects the firing of the neuron we are looking at a. RGC for RF It is arranged in center-surround in the receptive field Retina (picture 2) b. Cells in the Visual Cortex Oriented bar of light equals the best receptive field (Picture 3...
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