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Presented By: Mohsin Shad Registration Number: 2013-BC-005Presentation : Cell SignalingDate: 21-03-2016

Presented To:

Dr.Muhammad Tayyab

2Taste Receptor

3Taste 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

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.).

5Types of Tastes

Taste = ‘GustationBasic tastes: 1= Sweetness - outer tip of tongue2= 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

6Taste Modalities over Tongue

7Four 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

8Different ions or Receptors for Different Tastes

9Organ 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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11Taste 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

12Taste 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

13Neural 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

14Pathways 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

15Pathways 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

16Clinical Considerations

• Ageusia: Absence of sense of taste• Dysgeusia: Disturbed sense of taste• Hypogeusia: Diminished sense of taste• Hypergeusia: Increased sense of taste

17 Any Question ?

For Listening My Presentation