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Transduction of Environmental information

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Western University
Physiology 3120
Tom Stavraky

Human Physiology Monday, October 19, 2009 Transduction of Environmental Information • Humans have an array of sensory receptors on the skin (i.e. free nerve ending; Pacinian corpuscle)  Afferent axon = INTO the CNS  Becomes the presynaptic terminal on other axons that travel up into higher brain regions  Cell bodies located in dorsal root ganglia near spinal cord  Axon terminal of Pacinian corpuscle is surrounded by connective tissue  Sensory receptor: free/specialized nerve endings that is particularly sensitive to detect one form of environmental energy (i.e. modalities)  Receptors for pain & temperature are different  Adequate stimulus: particular form of energy to which a receptor is most sensitive  Receptors can still respond to different forms of energy, but we perceive any stimulation of these receptors as that of its adequate stimulus • Mechanisms of transduction  Mechanical stimulation: ion channels open up due to stretching  Chemical stimulation (i.e. pain  nociceptors): binding of ligand with receptor opens ion channels  Sometimes the same stimulus can be painful & non-painful (i.e. if your attention is elsewhere)  Thus, they are called nociceptors, not pain receptors  Photoreceptor: photon absorption leads to closing of ion channel • Generator (receptor potentials)  Stimulus causing opening of ion channel in axon terminal  Both sodium & potassium are free
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