GSU NEUR 3000 - NEUR 3000 - Chapter 12 (32 pages)

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NEUR 3000 - Chapter 12



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NEUR 3000 - Chapter 12

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Pages:
32
School:
Georgia State University
Course:
Neur 3000 - Hon Principles of Neuroscience

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THE SOMATIC SENSORY SYSTEM NEUR 3000 Dr Joseph J Normandin SOMATOSENSATION Touch is many different sensations Pressure Vibration Temperature Pain What else Collectively we call this somatosensation body sense Somatosensation like all senses begins with transduction at receptor cells THE SKIN Skin has three layers Epidermis protective outer covering Dermis somatosensory receptors connective tissue vascular network Hypodermis anchor for muscles some somatosensory receptors THE SKIN TRANSDUCTION OF TOUCH Touch is transduced by four different mechanoreceptors Pacinian corpuscles Vibration around 200 300 Hz Meissner s corpuscles Vibrations around 50hz Sense of texture Merkel s discs Points and edges Ruffini s endings Stretch The receptive fields of each mechanoreceptor and TRANSDUCTION OF TOUCH TRANSDUCTION OF TOUCH TRANSDUCTION OF TOUCH All of these mechanoreceptors use large diameter myelinated A primary afferent axons SOMATOSENSATION TOUCH DORSAL COLUMN FUNCTIONAL PATHWAY Axons from mechanoreceptors travel through the spinal cord to the brain Mechanoreceptor axons combine to form sensory nerves Sensory nerves combine and enter the spinal cord through the dorsal root Cell bodies of these neurons make up the dorsal root ganglion Bundles of axons continue to ascend the spinal cord forming the dorsal columns SOMATOSENSATION TOUCH DORSAL COLUMN FUNCTIONAL PATHWAY SOMATOSENSATION TOUCH DORSAL COLUMN FUNCTIONAL PATHWAY Axons from somatosensory neurons travel through the spinal cord to the brain In the brainstem dorsal root ganglion neurons synapse with dorsal column nuclei in the medulla These medullary neurons project to ventral posterior nucleus of the thalamus VP on the other side of the brain VP neurons send projections to primary somatosensory cortex S1 SOMATOSENSATION TOUCH DORSAL COLUMN FUNCTIONAL PATHWAY PAIN TEMPERATURE Pain is an unpleasant experience normally associated with tissue damage Pain evolved to help us avoid injury Our sense of temperature helps us to



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