Download - Taste Receptor
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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 ?
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