Chapter 6 - The Visual System & Chapter 7.1 - Principles of Sensory System Organization

Chapter 6 - The Visual System & Chapter 7.1 - Principles of Sensory System Organization

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SE&SORY SYSTEMS What is a Sensory System? Window to physical energies. Give rise to sensory perceptions. General plan of sensory pathways: receptor, thalamus (diencephalon), cortex (telencephalon). Basic function of sensory pathways: transduction and coding . Transduction: transformation of physical energy into neuronal activity. Occurs in Receptor neurons . Coding : Information about stimuli are represented (coded) in the patterns of activity (action potentials) of the neurons: intensity, duration. Different sensory systems: sensory modalities: Vision Audition Somatosensory Taste Smell Why do we have different modalities when the result of transduction of sensory stimuli for all modalities is the same: action potentials? Theory of specific sensory energies by Johannes Muller, 1826. Labeled pathways . Some receptors transduce and encode : somatosensory & olfaction Other receptors only transduce (do not generate action potentials): vision, audition, taste. RECEPTIVE FIELD: The activity of all sensory neurons can be modulated by stimulating a certain region of the sensory surface. This region is called the Receptive Field of the neuron. THE VISUAL SYSTEM (Chap. 6) Web links for Visual System: http://www9.biostr.washington.edu:80/cgi - bin/DA/PageMaster? atlas:NeuroSyllabus+ffpathIndex/Syllabus^Chapters/SUBJECTS/Visual+2
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http://epunix.biols.susx.ac.uk/Home/George_Mather/Linked%20Pages/Physiol/index.html The visual ssystem is one of the most studied sensory systems. Functions of the visual system : - Responds to questions: What (recognition) and Where (location)? -Generates 3-D perception of the world from a 2-D retinal image. Illusions, hallucinations. Visible light: Narrow portion of the spectrum of electromagnetic radiation. Waves (wavelength) or photons (particles). - Speed : 300,000 Km/sec; 186,000 miles/sec. Does not need a medium (air, water). - Visible spectrum : wavelength extends from 760 (red end) to 380 (blue end) nanometers (nm, billionth of a meter: 10 to -9). ( FIG 6.2). It can vary for different species. -Wavelengh of light associated with color perception. Frequency. -Intensity of light associated with brightness. Eye . It is an optical instrument similar to a photographic camera. Development of optic cup from diencephalon. It forms a 2-D image of the world onto the retina (FIG 6.4) Retina contains photoreceptors that tranduce light Having two eyes gives us the ability to create 3-D perceptions (depth perception through binoculat vision). The eyes can be moved with the help of three pairs of muscles . The two eyes move conjointly .
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This note was uploaded on 04/04/2012 for the course PSYCH 202 taught by Professor Kim during the Fall '06 term at University of Washington.

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Chapter 6 - The Visual System & Chapter 7.1 - Principles of Sensory System Organization

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