Signal Transduction in hair cells: Figure 10-21 Sensory coding for pitch: Figure 10-22 The Visual System F.1. Introduction : The visual system is the most complex of all sensory systems. The optic nerve contains 1 million of fibers, whereas the auditory nerve contains 30 000 fibers. That is more than all the dorsal root fibers entering the entire spinal cord. Visual perception occurs in 2 stages: • Light entering the cornea is projected onto the back of the eye to a specialized sensory organ, the retina. In the retina, the light is converted into an electrical signal. That step as you recall is the transduction. In this case, it is called phototransduction. • The electrical signal is then sent along the optic nerve to a higher center in the brain, the visual cortex, for further processing. F.2. Structure of the eye : (Fig. 10-28 a,b) The eye is an optical device designed to focus the visual image on the retina with minimal distortion. Neural pathways
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