Lecture20 - BioNB222 Cornell University Spring 2008 Carl D....

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BioNB222 Spring 2008 Cornell University Carl D. Hopkins 1 Lecture 20. Principles of Sensory Function The lecture will introduce general principles of sensory function, including transduction, threshold, intensity coding, receptive fields, adaptation, measurements of sensitivity, parallel pathways, lateral inhibition, and mapping. The somatosensory system will be used to illustrate major points. These principles apply to other sensory modalities as well. Reading Assignment Purves et al., (2007) Neuroscience, 4 th edition. Chapter 9. (Somatic Senses: Touch and Proprioception), pp. 207-229 Learning Objectives Be able to: 1) Explain the meaning of each of these terms: Transduction, Encoding, Intensity code, Rate code, Adaptation, Labeled Line, Lateral Inhibition, Receptive Field, Sensory Map. 2) Be able to explain how the nervous system is able to keep track of the following information about an external stimulus? a. WHAT is the external event or disturbance? b. HOW MUCH of a disturbance is there? c. WHERE is the stimulus in space? d. WHEN did the stimulus or disturbance start and stop? Lecture Outline This lecture focuses on the somatosensory system and our sense of touch. 1) Transduction. The conversion of external disturbance into a neuro-electric event (depolarization or hyperpolarization) What is the sequence of events that converts an external mechanical event into a neural event? a. Pressure deforms lamina membranes. b. Ion channels (mechanoreceptor proteins) open, allowing Na+ and K+ to flow through membrane. c. Transducer is a membrane protein linked to the cytoskeleton, and to an extra cellular anchor. Mechanical forces open channel allowing ions to flow through. Protein is unknown. d. The inward current is depolarizing. Depolarization confined to region of transducer molecules. Depolarization leads to encoding (spike generation). 2)
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Lecture20 - BioNB222 Cornell University Spring 2008 Carl D....

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