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Psychology (9,695)
PSYB51H3 (306)
Chapter 12

Chapter 12

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Matthias Niemeier

Chapter 12: Touch Touch: used to refer to sensations caused by mechanical displacements of skin Kinesthesis: perception of position and movement of our limbs in space Proprioception: perception mediated by kinaesthetic and vestibular receptors Somatosensation: collective term for sensory signals from body Pain: sophisticated warning system that tells us when something might be internally wrong or when external stimulus may be dangerous, enabling us to defend our bodies as quickly as possible Temperature sensations enable us to seek or create a thermally safe environment Touch Physiology The sense organ and receptor units for touch Human sense of touch housed in largest and heaviest of sense organs, the skin Touch receptors embedded all over body, in both hairless and hairy skin, mouths and muscles, tendons, joints Receptor units for touch embedded in both outer layer epidermis o Underlying layer dermis Each type of receptor can be characterized by 3 attributes: o Type of stimulation to which receptor responds Receptors respond to different stimulus events ie. Pressure, vibration or temperature changes o Size of receptive field Receptors activated when stimulation is applied to particular area of body, constitutes receptors receptive field Size of receptive field refers to extent of body area that elicits receptor response o Rate of adaption (fast vs. slow) Fast- adapting (FA) receptor responds with bursts of action potentials- when preferred stimulus is applied and when it is removed Does not respond during steady state between stimulus onset and offset Slow adapting (SA) receptor remains active throughout period during which stimulus is in contact with its receptive field Tactile Receptors Tactile receptors called mechanoreceptors because they respond to mechanical stimulation or pressure Consists of nerve fibers All tactile nerve fibers fall into class called A-beta fibers have wide diameters that permit very fast neural conduction Expanded endings of 4 different populations of tactile fibers in hairless skin of hand: o Meissner corpuscles: fast-adapting (FA 1) fibers that have small receptive fields o Merkel cell neurite complexes: slow-adapting (SA 1) fibers that have small receptive fields o Pacinian: fast-adapting (FA II) fibers that have large receptive fields o Ruffini endings: slow-adapting (SA II) fibers that have large receptive fields Endings of Meissner and Merkel receptors located at junction of epidermis and dermis Pacinian and Ruffini receptors embedded deeply in dermis and underlying subcutaneous tissue Kinesthetic Receptors Sensing where limbs are and what kinds of movements were making Angle formed by limb at joint perceived primarily trough muscle receptors muscle spindles o Convey rate at which muscle fibers changing in length Receptors in tendons provide signals about tension in muscles attached to tendons Ian Waterman o Cutaneous nerves that connected kinaesthetic and other mechanoreceptors to brain destroyed- cannot use limbs unless he can see them (in room with lights) www.notesolution.com
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