Taste bud

Taste buds Taste Profiles Taste receptors Tastes, primary... 

When food contains both sweet and bitter substances, the temporal pattern of reception, ie, the order in which sweet and bitter tastes are perceived, affects the total quaUtative evaluation. This temporal effect is caused by the physical location of taste buds. The buds responding to sweet are located on the surface and the tip of the tongue, the bitter in grooves toward the rear. Therefore, the two types of taste buds can be activated sequentially. 

The metallic taste (12,19,20) is not ascribed to any special taste buds or mouth area. Along with pungency (the hot taste of peppers), astringency (the puckering taste of alum), and cold taste (the cool effect of menthol), the metallic taste is called a common chemical sense (21). 

Simultaneous stimulation of the tongue with the appHcation of different taste stimuli produces an interaction, modification, or blending of the stimuli in some instances but not in others. Warm and cold sensations are reported to act similarly on the tongue in two groups bitter, warm, and sweet and sour, cold, and salty (24). The theory of the specificity of the taste buds may be subject to modification (25). 

In the tongue, ENaC is expressed in taste bud epithelial cells. The expression of a, (3 and y subunits at the apical membrane of taste buds is observed under low salt diet, known to greatly increase plasma aldosterone. This observation suggests that ENaC could play a significant role in the transduction of salt sensation. 

Sensory receptors expressed in particular in taste receptor cells of the taste buds that sense the five basic tastes salt, sour, sweet, bitter and umami (glutamate taste). Sodium type ion channels sense salty taste whereas sour taste is transduced by potassium type ion channels. The underlying cause of sweet, bitter, and umami tastes is the selective activation of different groups of G protein coupled receptors that discriminate between sweet, bitter, and umami tasting molecules. 

That the initial event of taste stimulation takes place on the cell surface of the taste receptor is now universally accepted. In addition, accumulated evidence strongly suggests that taste-bud stimulation is extracellular in nature. For example, (1) the sweet-taste response is both rapid and reversible, (2) the intensely sweet proteins monellin" and thaumatin could not possibly penetrate the cell, because of their size, and (3) miraculin, the taste-modifying glycoprotein, having a molecular weight of 44,000 would also be too large to penetrate the taste cell. ... 

Fig. 21.—Schematic Diagram of the Proposed Types of Bonding of Sweet Glycosides to the Taste-bud Receptor-sites. ...

Taste-modality recognition is a function of the cells of the taste buds. Perception of the sensation is a result of complex processes in the brain. The biological events that are discussed are those that occur, or are suggested as occurring, in taste-receptor cells, beginning at the instant when the taste-stimulus molecule interacts with the cell, until the membrane of the receptor cell is polarized. These are peripheral events. However, our knowledge of the peripheral mechanisms in taste perception is not sufficiently complete to provide a detailed, biophysical explanation of this phenomenon. Nevertheless, several stages in this explanation have been hypothesized, and some are demonstrable. 

Fig. 2.6 Rostral nasal anatomy of Honey Possum (Tarsipes rostratus) showing (a) section levels and (b) TS at level 4 naso-palatine papilla with taste-buds (TB), gustatory chemoreceptors facing lumen of N-Pd (incisive duct, Id) (from Kratzing, 1987).

In the squamous/stratified epithelium covering, the palatal aperture of the N-P canals and the dorso-lateral surfaces of the papilla, there are occasional clusters of taste buds. These non-olfactory chemosensory elements are positioned at or near to the entrance to the AOS, suggesting that some initial chemosensation may arise from the sampling of material... 

Hofer H.O. (1978). The ductus nasopalatinus and the ductus vomeronasalis, and the occurrence of taste buds in the papilla palatina in Nycticebus coucang (Primates, Prosimiae). VerhAnat Ges 72, 649-650. 

Johnson E.W., Eller P.M., Jafek B.W. and Norman A.W. (1992). Calbindin-like immunoreactivity in two peripheral chemosensory tissues of the rat taste buds and the vomeronasal organ. Brain Res 572, 319-324. 

Kratzing J.E. (1987). The presence of rostral palatal taste buds in mammals. Aust Mammal 10, 29-32. 

Schwenk K. (1985). Occurrence, distribution, and functional significance of taste buds in lizards. Copeia, 91-101. 

The dosage forms most commonly employed for pediatric formulations are liquids and chewable tablets. A perceived unpleasant taste is much more evident with these dosage forms than when a drug is administered as a conventional solid oral dosage form. Second, it is widely believed that children younger than the age of 6 years have more acute taste perception than older children and adults. Taste buds and olfactory receptors are fully developed in early infancy. Loss of taste perception accompanies the aging process. 

Miscellaneous Decrease number of taste buds Increase dysfunction and cancer... 

Approximately 99.5% of saliva is water. Swallowing is facilitated by the moistening of food materials furthermore, it serves as a solvent for molecules that stimulate the taste buds. The presence of mucus, which is thick and slippery, lubricates the mouth and the food and assists in swallowing. Lysozyme is an enzyme that lyses or kills many types of bacteria that may be ingested. 

Taste receptor cells are organized into taste buds 825 Sensory afferents within three cranial nerves innervate the taste buds 826 Information coding of taste is not strictly according to a labeled line 826 Taste cells have multiple types of ion channels 826 Salts and acids are transduced by direct interaction with ion channels 826 Taste cells contain receptors, G proteins and second-messenger-effector enzymes 827... 

Taste receptor cells are organized into taste buds. The... 

The taste bud is a polarized structure with a narrow apical opening, termed the taste pore, and basolateral synapses with afferent nerve fibers. Solutes in the oral cavity make contact with the apical membranes of the TRCs via the taste pore. There is a significant amount of lateral connectedness between taste cells within a bud both electrical synapses between TRCs and chemical synapses between TRCs and Merkel-like basal cells have been demonstrated to occur [39]. Furthermore, there are symmetrical synapses between TRCs and Merkel-like basal cells [39]. In addition, these basal cells synapse with the afferent nerve fiber, suggesting that they may function in effect as interneurons [39]. The extensive lateral interconnections... 

FIGURE 50-7 Rattongue, taste papillae and taste buds. (A) Surface of the rat tongue showing location of the taste papillae. (B) Cross-section of the three main types of taste papillae fungiform, foliate and vallate. (C) The taste bud contains 50-100 taste cells, including receptor cells and basal cells. 

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