Chapter 10.docx - Chapter 10 1. General Principles of...

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Chapter 101.General Principles of Sensory Physiologya.Afferent Branch of Peripheral Nervous Systemi.Information from periphery to CNS1.External environmenta.Sensory (outer surface)2.Internal environmenta.Visceral afferent (w/in body)b.Everything but CNSb.Sensory Informationi.Somatic Sensation (whole body)1.Somesthetic- pain, touch, vibration2.Proprioception- knowing/awareness of body positionii.Special senses (not centralized)1.Vision2.Hearing3.Equilibrium4.Taste5.Smellc.Perceptioni.Conscious interpretation of external worldii.Sound is faster than visioniii.Brain fills in the gapsd.Receptor Physiologyi.Sensory receptorsii.Transduction1.Conversion of stimulus energy into electrical energy (Action potential)2.Modalitya.Energy form of stimulus3.Sound waves, light waves4.Ex: microphonesound5.Ex: sound waves enter earamplification at ossiclesnerve sendssignals to brain (hair cells)iii.Law of Specific Nerve Energies1.Receptors show specificity to one modality2.Adequate stimulusa.Modality for which a receptor is specificb.Modality to which receptor is most sensitive3.Photoreceptors respond best to lighta.But add enough energy then it can be createdi.Ex: hit on the headsee starsiv.Receptor Potentials (potential on post-synaptic membrane)1.Change in membrane potential in response to a stimulus acting onsensory receptora.Graded potentialb.Caused by opening and closing ion channels
c.If greater than threshold, can generate action potentialsv.Adaption1.Decrease in amplitude of receptor potential over time in presence of aconstant stimulus2.Corresponding decrease in frequency of action potentials3.Decreases perception of stimulusa.Want this in bad smellsb.Don’t want it for clothing sensationc.DIAGRAMvi.Receptor Types1.Specialized Nerve Endinga.Naked or modifiedb.Ex: pressure receptor2.Separate Cella.May or may not be a neuron as receptorb.Neurotransmitterc.Ex: muscle celle.Sensory Pathwaysi.Labeled line theoryii.Specific neural pathway for each sense1.Wires dedicated to particular modalityiii.Cortical Sensory areas1.Olfactory, visual, auditory, gustatory, somatosensory, vestibular cortexiv.Sensory Unit1.Single afferent neuron, plus all receptors associated with ita.Receptor field associated with afferent neuron2.All receptors are of same type3.Acton potential may result from activation of receptorsv.Sensory Units and Receptive Fields1.DIAGRAMvi.General Sensory Pathway1.DIAGRAM2.CNSa.Cortex3rdOrder NeuronThalamus (relay station)second order neuronspinal cord of brain stem3.PNSa.afferent neuron (1storder)receptorsStimulusf.Sensory Codingi.Stimulus type1.Receptor type activated2.Specific pathway3.Synestesiaa.Ex: see and taste musicb.Association of other sensesii.Stimulus intensity1.Two ways: spatial and temporal
2.Frequency of action potentials3.Recruitmenta.Population codingi.Also called recruitmentii.Stronger stimulus activates more receptors1.Can be from same afferent neurons2.

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