BearCh12-ACRQedt - Chapter 12 The Somatic Sensory System...

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Chapter 12 – The Somatic Sensory System Answers to Chapter Review Questions Page 1 of 4 Copyright © 2007. Lippincott Williams & Wilkins. Ancillary material to accompany Bear et al.: Neuroscience: Exploring the Brain, 3e Question 1: Imagine rubbing your finger across a pane of smooth glass and then across a brick. What kinds of skin receptors help you distinguish the two surfaces? As far as your somatic sensory system is concerned, what is different about the two surfaces? Answer: Smooth glass might produce a stimulus with no vibrations and no changes in pressure. To detect this surface, mechanoreceptors, such as Merkel’s disks or Meissner’s corpuscles, should be close to the surface of the skin. To be detected, the stimulus that glass creates would have to excite slowly adapting mechanoreceptors because its surface does not change. Merkel’s disks are slowly adapting and have small receptive fields. A brick might produce a stimulus with vibrations and changes in pressure related to the raised parts of its surface. This is a good stimulus for the Pacinian corpuscles and Ruffini’s ending. To detect the successive peaks and valleys on the surface of the brick, a rapidly adapting receptor might best detect the stimulus. This requirement might make a Pacinian corpuscle the ideal receptor for this stimulus because Pacinian corpuscles are rapidly adapting, whereas Ruffini’s endings are slowly adapting. Question 2: What purpose is served by the encapsulations around some sensory nerve endings in the skin? Answer: Encapsulations around Pacinian corpuscles provide a mechanism that makes the Pacinian corpuscles rapidly adapting, which is a property that makes them sensitive to vibrating high-frequency stimuli. If the encapsulations are stripped away, as done by Loewenstein and colleagues in the 1960s, the naked nerve terminals become less sensitive to vibrating stimuli and more sensitive to steady pressure.
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This note was uploaded on 09/09/2009 for the course SPHSC 449 taught by Professor Peter during the Summer '09 term at University of Washington.

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BearCh12-ACRQedt - Chapter 12 The Somatic Sensory System...

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