Exam 2 Notes - Biopsychology Exam 2 Notes Lecture 1- Visual...

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Unformatted text preview: Biopsychology Exam 2 Notes Lecture 1- Visual System I Transduction The conversion of one form of energy to another Law of Specific Nerve Energies Developed by Johannes Muller The activity of a particular nerve always conveys the same kind of information to the brain Details of the perception are supplied by the pattern, timing, and strength of the activation The Eye Thalamus serves strategic role in gating of information flow to the cortex (occipital) Light falls onto the photoreceptors found along the retina Light enters the eyes through pupil It is focused by the lens and cornea and projected to the retina Light passes through ganglion and bipolar cells and to the receptors. Messages from the receptors go to the bipolar cells which in turn convey the messages to ganglion cells Bipolar cells Receive input from 2-3 cones and involves great precise detail and little responsiveness to dim light Receive input from hundreds of rods and involves little precise detail and great responsiveness to dim light Ganglion cells Receive input from several bipolar cells X cells o Found near the fovea and have small receptive fields Y cells o Found in the periphery of the retina and have large receptive fields o Get most input from rods and insensitive to color differences Ganglion cells axons join together and travel to the brain through the optic nerve Blind spot is the region where the optic nerve leaves the eye and has no receptors because blood vessels and ganglion cell axons pass through that region Completion: filling in of the gaps of the retinal images Receptors (20 Rods to 1 cone) Cones- low convergence in cone-fed circuits More sensitive to color and useful in bright light Photopic vision Abundant in and near the fovea Contain photopigments that release energy when struck by light Rods- high convergence in rod-fed circuits Abundant in the periphery region of the retina Sensitive to dim light Scotopic vision Contain photopigments as well Visual Transduction The conversion of light to neural signals by the visual receptors Photopigments are transformed by light, causing a G-protein mediated decrease in sodium (Na+) permeability Rhodopsin- a lipid (retinal) and a protein (opsin) pigment found on receptor cells In the dark Rod is depolarized as cyclic GMP holds ion channels open and cations enter inside the cell. (NT released into inhibitory synapse) Phosphodiesterase is inactive Inhibitory neuroreceptor of the bipolar cell is open, membrane hyperpolarized, and no neurotransmitter released (no action potential) In the light Rod is hyperpolarized as cyclic GMP is destroyed by phosphodiesterase and ion channels close. (no NT released into inhibitory synapse of bipolar) Rhodopsin is split as light strikes on it Inhibitory neuroreceptor of the bipolar cell is closed, membrane...
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This note was uploaded on 11/11/2010 for the course PSY 308 taught by Professor Jones during the Spring '08 term at University of Texas at Austin.

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Exam 2 Notes - Biopsychology Exam 2 Notes Lecture 1- Visual...

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