1) Taste is mediated by taste receptors located in taste buds in the oral cavity and throat. Taste receptors respond to different ions and molecules to produce the sensations of sweet, salty, sour, bitter and umami. 2) Taste buds contain 50-75 taste receptor cells that sample substances in the mouth and transmit signals through nerves to the brainstem and thalamus, which process taste and initiate behavioral responses. 3) The tongue is the major organ of taste, containing fungiform, foliate and vallate papillae that house taste buds. Taste signals are conveyed to the brain via the facial, glossopharyngeal and vagus nerves.

1. Presented By:
Mohsin Shad
Registration Number:
2013-BC-005
Presentation :
Cell Signaling
Date:
21-03-2016
Presented To:
Dr.Muhammad Tayyab
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2. Taste Receptor 2

3. Taste Receptor
• Receptor that facilitates the sensation of taste.
• When food or other substances enter the mouth
• Molecules interact with saliva and are bound to taste
receptors
• Present in Oral cavity and throat.
• It is type of chemoreceptors that is present on taste buds
• Taste buds- epithelial cells that act like neurotransmitters
• Innervated by cranial nerves
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4. Taste
• Taste (‘gustation’) is often referred to as the chemical senses
• They are mediated in the first instance by receptors that are
stimulated by chemical substances.
• Receptors are called ‘ chemoreceptors
• Taste: Chemicals dissolve in our mouth (must be water soluble)
and stimulate the taste buds in the oral cavity (tongue, soft
palate, cheek, etc.).
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5. Types of Tastes
Taste = ‘Gustation
Basic tastes:
1= Sweetness - outer tip of tongue
2= Saltiness - lateral edge of tongue behind tip
3= Sourness - lateral edge of tongue behind saltiness region
4=Bitterness - back edge of tongue toward throat
5= Umami - taste of glutamate - not localized
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6. Taste Modalities over Tongue 6

7. Four Major Sensations of Taste
• Sweet- G-protein activates second messenger system
• Bitter- also G-protein activated specific receptor
• Sour- proton channel (acids taste sour)
• Salty- sodium channels Tastes seem to be enhanced in different
parts of the tongue
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8. Different ions or Receptors for Different Tastes
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9. Organ of Taste
• The tongue is the major organ of gustation
• There are also some taste buds on the palate, pharynx, and
epiglottis
Papillae - contain taste buds
• Fungiform papillae (mushrooms) - top surface of tongue
• Foliate papillae (ridges) - rear, lateral margin of tongue
• Vallate papillae (pimples) - rear, medial margin of tongue
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11. Taste buds
• Only 1% of the epithelial cells on tongue’s surface are taste buds
• Contain 50 to 75 sensitive cells each
• Taste-sensitive cells have a limited lifetime, and are constantly being
replaced.
• Taste pore permits substances to enter
• Three cell types in each taste bud:
• Taste receptors – chemoreceptors
• Basal cells - source of new taste receptors
• Gustatory afferent fibers - conduct action potentials to brain
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12. Taste cells – Taste Receptors
• Come from the division and differentiation of the basal cells
• Not neurons in the strict sense, but have synapses with gustatory afferent
fibers
• Arrival of chemical molecules on surface leads to change in membrane
potential - receptor potential
• Most taste receptors respond to at least two of the basic tastes
• Sometimes taste receptors generate action potential
• Transduction differs for each type of taste receptor
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13. Neural Pathways for Taste
• Afferents
• Anterior 2/3 of tongue - VII (facial nerve)
• Posterior 1/3 of tongue - IX (glossopharyngeal nerve)
• glottis, epiglottis, pharynx, palate - X (vagus nerve)
• All afferent fibers end in gustatory nucleus in the medulla
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14. Pathways to the Brain
• Taste fibers proceed along several pathways to the medulla oblongata or
brain stem, then to the thalamus, and finally to the taste area on the
anterior cortex.
• For taste sensation, gustatory nucleus neurons send fibers to the ventral
posterior medial nucleus (VPM) of thalamus
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15. Pathways to the Brain
• VPM sends fibers to the primary gustatory cortex ( Brodmann's area 43
in ventral parietal lobe
• For autonomic functions, gustatory nucleus sends fibers to the many
brainstem regions involved in swallowing, salivation, gagging, vomiting,
digestion, respiration and to the hypothalamus and amygdala
• appetite and food preferences
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16. Clinical Considerations
• Ageusia:
Absence of sense of taste
• Dysgeusia:
Disturbed sense of taste
• Hypogeusia:
Diminished sense of taste
• Hypergeusia:
Increased sense of taste
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17. 17Any Question ?
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