Ch12 Neuro Notes - Chapter 12- The Somatic Sensory System...

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Chapter 12- The Somatic Sensory System Somatic sensation- enables our body to feel, ache, chill, and know what different parts are doing all sensations except seeing/hearing/tasting/smelling/vestibular sense of balance Sensitive to pressure against skin, position of joints a muscles, distension of the bladder, and temperature of the limbs and brain Responsible for pain Different from other sensory systems because o 1. Receptor are distributed throughout the body (not small, specialized locations) o 2. Responds to touch, temperature, pain, and body position P.388 Sense of touch and sense of pain both depend on different receptors and different axonal pathways Proprioception- sense of body position- used to control muscle reflexes (ch13) Touch Skin o Largest Organ o Protection function o prevents evaporation of body fluid into dry environments o Hairy and glabrous (hairless) o Epidermis- outer layer o Dermis- inner layer
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FIGURE 12.1 Mechanoreceptors of the Skin Mechanoreceptors - sensitive to physical distortion such as bending or stretching\ o most of the sensory receptors o monitor contact with the skin, pressure in the heart and blood vessels, stretching of digestive organs and urinary bladder, force against the teeth o different mechanical sensitivities of mechanoreceptors mediate different sensations o has unmyelinated axon branches each has a mechanosensitive ion channels - gating depends on stretching or changes in tension of the surrounding membrane 4 Somatic Sensory Receptors Pacinian Ruffini’s endings Meissner’s Merkel’s Disks Krause end
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corpuscle corpuscles bulbs Deep within the dermis Big enough to see with the naked eye Large receptive fields Rapidly adapting Sensations about 200-300 Hz More sensitive to high frequency stimuli Slightly smaller than the pacinian corpuscle Found in hairy and glabrous skin Large receptive fields Slowly adapting More sensitive to low frequency stimuli Located in the ridges of glabrous skin Raised part of fingerprints Small receptive fields (few mm) Rapidly adapting Sensations about 50 Hz Located within the epidermis Consists of nerve terminal and a flattened, non- neural epithelial cell (has a synapse-like junction with the nerve terminal) Small receptive fields (few mm) Slowly adapting Lie at the border of regions of the skin and mucous membrane- nerve terminals look like knotted balls of string FIGURE 12.2 and 12.3
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This note was uploaded on 09/24/2011 for the course NEURO 302 taught by Professor Ritter during the Fall '10 term at Washington State University .

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Ch12 Neuro Notes - Chapter 12- The Somatic Sensory System...

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