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Lec 5 : Somatic Sensory System (nearly word-for-word what was said in lecture)

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Lec 5The Somatic Sensory SystemSlide 5Somatic sensationoActually multiple modalities touch proprioception pain temperatureoTouch pain temperature skip proprioception another aspect of somatosensationlook at with motor controloEfference not this weekoHaptics perception conveyed by touch in combo w motor control that is active exploration of objects because of the way that you control your fingers when you touch something also gives you info about where something is located also gives much more vivid impression of shapesize of objects where touch plays a role in interaction w objects such as in recognizing them touching something in darkness reading BrailleoTouch often goes together with motor controloEnables body to feel itselfenviro ache chilloSomatic sensory systemdiff from other systemsReceptorsdistributed throughout esp on skin surfaceResponds to diff kinds of stimuliSlide 6TouchoWhat receptors are involvedoPrimary afferent neuronsRelay info directly from skin to the brain may have very long axons if coming from footoSpinal cordoWhich pathways subserve touchoSomatosensory cortexoSlide 7Types of skinoHairy vs glabrous hairlessLayers of skinoEpidermis outer vs dermis innerFunctions of ksinoProtective fxnoPrevents evaporation of body fluidsoProvides direct contact w world give info about touchmechanoreceptorsMechanoreceptorsoIn dermisoMajority of somatosensory receptors are mechanoreceptorsoNot just skin also found in heart blood vessels organs gumoUnmyelinated axon branches w mechanosensitive ion channelsSlide 8Mechanoreceptor typesScientistsTypeInfoGermanMeissners near top of dermis under epidermissurfaceCorpusclesMerkels Disksconnects to a cell that isnt a nerve itselfItalianPacinian corpusclesRuffinis endingsIn skin covered with mucus have other receptors like Kraus end bulbs similar to Merkels disks but they have bulbs at the endSlide 9Mechanoreceptors look different and differ in what they do and in terms of spatial resolution receptive fields tend to differResearchoRecording from individual axons in this case the median nerve stimulated the hand to figure out where does this axon show responsiveness where can you get APsoFor Meissners corpuscles you get very small receptive fields Pacinian corpuscles much larger receptive fieldscan be due to the fact that individual nerve endings are designed differently or due to it going to diff placesSlide 10DifferencesoDiffer in terms of receptive fields Meissners corpuscles and Merkels Disks have smaller receptive fieldscould be bc theyre closer to epidermis the deeper you go the more diffuse the responsiveness will be although there are other reasons for why they have MM have small receptive fieldsoDiffer in terms of time Meissners corpuscles and Pacinian corpuscles have higher degree of adaptationCurve some kind of mechanical force as a function of timeonly see APs at the initial point but not when the mechanical force is maintained and then it briefly responds again as the pressure is released this is even more true for Pacinian corpusclescouple APs at the onset of mounting pressure and then it discontinues
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