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Lecture 11

Lecture 11 - Chemical Senses: Taste & Smell

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Human Biology
John Yeomans

HMB200H1S L11 Feb 14 2012IXback of tongue pharynxsensory info from Chemical Senses TasteSmelltonguethroatVIIIXsensorymotor salivationEvolutionary change from fast to slow signaling Food particles dissolve in saliva analyzedmemoriesTaste recs in both of these CNs Solitary tract separate anatomically from Brain Evolution Theorytrigeminal infordWe are the accumulation of mechanisms that Anterior 3 of solitary nucleus from VIIIXallowed our ancestors to survive and reproduce their Other 23 has all other info via CN X vagusgenes Carl Sagan eg melanopsinSomatotopic map within midbrainmedullaAll animals including humanMap from tip of tongue to viscera internal surface of Start w simple mechs for reproduction and body on solitary nucleusmap of internal worldsurvivalSeparate from map of external world on other Slower for more complicated infonucleiEx melaopsin telling when light on or offrods Relays up to forebrainthalamusprimary taste conesorganize special imaging lensinfo in taste zone of cortex most ventral of anterior Help particular animal find particular niche to parietal lobe and insular cortex part of visceral survive and reproducecortex important for emotionsReflexes use fast mechanisms for survivalVery important for feedingrelays to hypothal to tell Vision and olfaction use slower Gprotein what things taste linkcombined w info from mechanisms for survival Whyespecially slowgastrointestinal tractincrease secretions ex Visualcgmp gcoupled transducinsaliva gastric juices in GI tractBut provides more info ex colour spaceVisceral SensationsChemical systems for more detailed info about world in terms of chemicals1000s of chemicalsNeed more types of recs and more types of analysisEx lightdif freq sensitivies allow for colour visionHundreds of recs for smellProject more to telencephalonolfactory goes directly via CN1Optic to midbraindiencephalon3D info about worldTelencephalonanalysis via visual cortex later evolving and olfactory systemChemical vs mechanical sensesAnalysis of chemicals Taste and olfactionhypothalamus and visceral sensationAnalysis of distant world in TelencephalonTaste PathwaysVaguswandering from medulla to neck thorax abdomen connects w most of the viscera ex stomach liver intestines longTaste SensationsFastslowFast sensation following by slower but longerlasting rich sensation then olfactory for flow of taste infoSaliva important for dissolving tastantsCNs VII tipIX back SensationsalivationSaliva important for dissolving tastants need to be carried to recs by salivaAlso induce salivationparasympathetic motor responseSo sensory activation of recs activates reflex for salivaQuick so get saliva you need to sense foodStudied by PavlovCNs VII IX XVIIfacial muscles tips of tongueSalt sourfast recs activating fast ionotropic signals
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