2019 02 11Bio 3303 Chemoreception Notes.pptx -...

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AnnouncementsExam TeaserThe AP is the single method of communication used by sensory neurons. How does AP encode forModality, Intensity, Location and Duration?BIO 3303
AnnouncementsMidterm #1 Exam will be returned todayBIO 3303
Last Lecture HighlightsSensory system is composed of sense organs, afferent sensory neurons and the area of the brain to which these neurons projectSensory receptorsand sensory proteins work together to detect incoming stimuliClassification of sensory receptors: exteroceptors and interocpetorsClassification of sensory receptors based on modality: Chemo, mechno, light, temp, magnetic, electricalSensory neuron vs. epithelial sensory receptorSensory encoding with APs, Modality, Intensity, Location and DurationStimulus response relationshipsLateral inhibitionStimulus duration and receptor adaptationBIO 3303
D. Encoding Stimulus DurationFig. 6.5/7.6Tonic receptors: fire APs as long as the stimulus continues→ convey information about how long the stimulus lastsReceptor adaptation: AP frequency declines even when the stimulusintensity is maintained at a constant levelPhasic receptors : fire APs only when the stimulus begins (adapt quickly)→ convey information about changes in stimulus but not duration
Receptor AdaptationFig. 13.6, Hill et. al. 2004g.Pacinian corpusculeMechanoreceptor, sensitive only to changes in pressurePhasic response due to peripheral filtering from lamellae (accessory structure)Lamellae (“onion skin”) separated with fluid act as a filter:fluid redistributes, relieving initial distortion of sensory terminalIf lamellae removed: pacinian corpuscule act more as a tonic receptor.→ Other mechanisms of adaptation depend on changes in the neuronal membrane or channels
Chemoreception
Lecture ObjectivesBIO 3303By the end of this lecture, you should understand…The difference between taste and smellThe 5 categories of taste and their transduction mechanismsOlfactory reception and combinatorial encodingOlfactory diversity across speciesVomeronasal organ
ChemoreceptionMany types of chemoreceptors used to sense internal and external chemical environmentsChemoreception key for physiological regulation and to respond to our external environmentRegulating composition of body fluidsnavigationIdentify food, avoid toxins, make the most nutritionally rewarding choicesAvoid predators/ find preyCommunication with conspecifics (e.g. finding mates, conspecific recognition, alarm signal)
Types of chemoreceptorsChemoreceptor: cell specialized for transduction of environmental chemicalsInternal chemoreceptors:→ detect changes in O2, CO2 and pHExternal chemoreceptors:→ detect airborne and dissolved chemicals (olfaction and gustation)
Chemoreceptive organs in terrestrial mammalsGustation: Taste budsOral cavity (especially tongue, also larynx, sof palate)EsophagusOlfaction:i) Odorants: Olfactory epitheliumii) Pheromones: Vomeronasal organ (vestigial in humans)Fig. 6.8/7.9

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