Gustation (taste)

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Gustation (taste)

  1. 1. Anatomy ofTastePapillae Circumvilliate Folliate Filliform Circumvilliate Fungiform Folliate Filliform Fungiform Anthony J Greene 2
  2. 2. GUSTATORY SENSATION• It is a chemical sense and gives taste of foodor not-food materials•Substance to be tasted should either be in asolution or diluted with saliva•Taste must be distinguished from flavor whichincludes olfactory, thermal and tactileattributes of food in addition to taste•Taste stimuli are detected by taste receptors- 1. Tongue 2. Mouth 3. Pharynx
  3. 3. TASTE BUD•Sense organ for gustation is taste bud•Present on dorsum of tongue [ except filiform papillae ] ,palate, epiglottis, and in pharynx and larynx to a extent•Flask shaped with receptor cells and supporting cells•Each receptor cells live for 10 days after which it isreplaced by new cell from basal cells•Receptor cells have 6 to 18 hair like projections calledmicrovilli which has the receptors on its membrane•The base of the receptor cells are in contact with afferentnerve endings•Anterior 2/3rd is supplied by facial nerve and the posterior1/3rd by the glossopharyngeal nerve, the vagus nervesupplies the taste buds present in larynx
  4. 4. TasteAnatomy Anthony J 5 Greene
  5. 5. PATHWAY•The primary sensory neurons are situated in thegeniculate ganglion [ 7th nerve ] petrous ganglion [ 9thnerve] nodose ganglion [10th nerve]•The axons from these neurons enter into the medullaand end in the nucleus of tractus solitarius and secondorder neurons start here•Fibers from the NTS join the medial lemniscus andproceed upwards to ventral posteromedial nucleus ofthalamus, where 3rd order neuron arise•The fibers go to cortical area for taste sensation in thesomatosensory cortex
  6. 6. PATHWAY
  7. 7. STIMULI•Substances must dissolve in saliva before they canstimulate taste receptors•Four basic types of taste sensation 1. Sweet sensation  Organics [ sugar, glycols, aldehyde]  Tip of tongue 2. Bitter sensation  Alkaloids [ quinine, caffeine ] harmful  Back of tongue 3. Salty sensation  Anions of ionizable salts [ NaCl, NaBr etc ]  Front half of each side of tongue 4. Sour sensation  Acids [ acetic acid, tartaric acid etc]  Posterior half of each side of tongue
  8. 8. SOME FEATURE OF TASTE SENSATION•Threshold concentration for taste sensation for different substances are differenteg; for NaCl it is 2000mmol/L whereas for strychnine 1.6mmol/L•Taste sensation shows contrast, a sweet substance taste more sweet if takenafter a bitter substance, this is called successive contrast. If salt is placed on oneborder of the tongue then sensitivity for sweet substance increases in the otherborder and is named as simultaneous contrast•Adaptation is another important feature, if sweets are taken before tea with theusual amount of sugar, then the tea tastes less sweet due to adaptation•After taste is an interesting phenomenon , if miraculin a plant protein is taken firstand then any sour substance taken tastes sweet•Some abnormalities are 1. Ageusia = absence of taste sensation 2. Hypogeusia = decreased taste sensation 3. Dysgeusia = disturbed taste sensation
  9. 9. THANK YOU

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