Aspects in the Perceptual Functioning of Taste - Essay Example

Physiological and Psychological Aspects in the Perceptual Functioning of Taste School: Introduction Out of the five common senses, taste is thought to be one of the simplest sense channels, but it is not. This is because there are no rods, cones or the lenses used for the intake of sensory information. Further, there are no miniscule bones or tympanic membranes that are directly related to the sensory function of taste (Beckman, 2004). Due to the complexity of the sensory function of taste, scientists know more about the sense of hearing and sight than they know about taste, despite the fact that these others are highly complex sensory functions. Taste, also called gestation is a chemoreception that falls among the five senses. Taste is the ability to construe the flavour of different compounds, including poisons and foods (Beckman, M., 2004). In humans, similar to the case of many vertebrates, taste works closely with the sense of smell, during the interpretation of different flavours at the brain (Prescott, Johnstone & Francis, 2004). The perception of taste is among the sensory working of the nervous system; in humans, the receptor cells for taste are located on the tongue. This paper will explore the physiological and the psychological aspects involved during the actualization of the sensory function of taste. Background of the psychological and the physiological aspects of taste The mystery and the controversial nature of taste arises from many factors, among them, the fact that many people confuse taste and flavour. By definition, taste is the chemical based sensory perception made by dedicated receptor cells that form part of human taste buds. On the other hand, flavour works through the blending of different senses. During the process of perceiving flavour, the human brain construes gustatory stimuli (primarily taste) thermal and tactile sensations as well as olfactory stimuli, which are related to smell (Silver, et al., 2008). In the case that an individual is taking foods that are spiced, the brain does the extra work of perceiving pain, as an extra component featured in the interpretation of flavour. The mystery surrounding the function of taste, also, arises from the factor that the testing of taste sensations is highly subjective in nature; taste is likely more subjective than the other sensory functions. For example, some individuals are known to inherit traits that make them to find some foods nauseating (Beckman, 2004). Still, others who have been identified as supertasters are known to possess highly concentrated taste receptors, to the level that they perceive plain food as being fully flavoured. Additionally, it is general knowledge that different foods taste differently from one person to another; many people may not prefer the same food flavours (Silver, et al., 2008). The conversion of taste sensation to its perception counterpart The taste function starts during the sensation of taste, which takes the form of electrical impulses. Sensation refers to the responses offered in response to different forms of stimuli, which could take the form of chemical composition, light or pressure. These sensations are converted into perceptions, which are classified as vision, touch or taste, after the sensations reach the brain and are interpreted in specific ways. The sensation of different stimuli triggers the activation of different sensory clusters or sensory receptors. For example, the sensation of chemical stimuli triggers the activation of the chemoreceptor cluster which is tasked with the perception of olfactory and gustatory stimuli (Sugita, 2006). Due to the facts that smell and taste are, primarily, reactions that are triggered by the chemical composition of different foods or solutions, the sense of smell and taste are highly related (Prescott, Johnstone, V & Francis, 2004). However, in the case of some animal species, the chemical senses of smell and taste are merged into one. For example, in the case of worms, which are invertebrates, there is no differentiation between the receptors for olfactory and gustatory stimuli (Prescott, Johnstone, V & Francis, 2004). The function of taste in humans In the case of humans, gustatory receptor clusters of cells are responsible for the detection of taste. The taste bud of a human tongue is composed of approximately 50 receptor cells, supporting and basal cells. These taste buds are enclosed in the cup-shaped papillae (Beckman, 2004). These papillae are the small bumps that appear like dots on the surface of the human tongue. Some of these papillae bumps help to maintain a level of friction between the surfaces of the tongue and that of the food being ingested (Beckman, 2004). All the gustatory receptors contain a thin gustatory hair, which protrudes from the surface. The clusters of taste hairs extend to the outside of the taste cells, across taste pores, which are openings found on the surface of the gustatory receptors (Hunter, 2002). Upon the ingestion of food into the mouth, food molecules mix with saliva, which enables them to enter the taste pores of the different gustatory receptors, where they interact with the taste-sensing gustatory hairs. The interaction between these hairs and the food molecules triggers the taste sensation associated to the particular food or compound (Sugita, 2006). After the taste stimulus triggers the activation of the gustatory impulse, the respective receptor cells send a signal to the responsible neurons, which transmit an electrical signal to the gustatory centre located at the cerebral cortex (Hunter, 2002). Upon the reception of the electrical signal, the brain interprets the particular sensation as a distinctive taste, and classifies it according to the taste blue print established in the past (Beckman, 2004). The taste blueprint is based on the classification of the four basic tastes, which include salty, sweet, bitter and sour. These four tastes are the foundational roots of the different tastes, and the four of them trigger the activation of a designated gustatory receptor (Sugita, 2006). Basic taste and the physiological detection of taste For long, science proposed that there were four primary tastes, including sourness, sweetness, bitterness and saltiness; more recently, savouriness (umami) has been proposed as the fifth root taste (Nelson, et al., 2002). This taste is exemplified by the non-salty sensations triggered by the ingestion of monosodium glutamate (Nelson, et al., 2002). The sensations of the different tastes are triggered at the different areas of the oral cavity; this is contrary to the traditional misconception that different areas of the tongue are dedicated for the detection of different tastes (Lindemann, 1999). However, slight differences in the sensitivity of the different areas of tongue can be verified; these variations do not conform to the traditional tongue map explicitly. The receptors for salty and sour tastes are ion channels; the receptors for bitter, sweet and umami tastes fall under the cluster of G protein-coupled receptor cells (Doty, 2003). The sensation of saltiness arises from the presence of sodium ions, which move through the tongue’s ion channels, triggering an action potential. In the case of sourness, it is the one that identifies the presence of acidity (McClure & Lawless, 2007). The mechanism used for the detection of acidity is similar to that of detecting saltiness; hydrogen ion canals perceive the concentration of acids, due to the presence of the hydrogen ions formed by the combination of water and acids (McClure & Lawless, 2007). Sweetness is triggered by the presence of some proteins, sugars and other compounds. Sweetness is detected by the G protein-coupled receptors that are attached to the G protein gustducin available at the taste buds (Doty, 2003). Bitterness is perceived to be sharp or unpleasant by many people, and is common for compounds and foods like coffee, beer and quinine. Past studies have shown that type 2 taste receptors attach to G protein gustducin to allow an individual to get the sensation of bitter substances (McClure & Lawless, 2007). Umami is triggered by glutamate among other compounds, and the sensation of this taste is common in aged or fermented foods. Some of the taste buds that detect umami respond in a way similar to that of sugar; the glutamate attaches to G Protein receptors variants to trigger the sensation of the taste (Doty, 2003). Conclusion Out of the five common senses, taste is thought to be the simplest, but it is indeed more complex than hearing or sight, which has been deeply explored. The complexity of taste arises from the fact that, it is often confused with flavour, which works through the blending of different senses. The detection of taste starts with the sensation, which triggers the communication of electrical impulses to the brain, and the impulses are perceived as different taste variants. In humans, the taste function starts with the interaction of gustatory hairs with food or compound molecules, which triggers the sensation which is interpreted as taste at the brain. In addition to the four basic tastes, scientists have added a fifth taste called umami. The sensation of the different tastes takes place through different physiological channels, where salt and sour tastes are perceived through ion channels and bitter, sweet and umami tastes are communicated by G protein receptors. References Beckman, M. (2004). A Matter of Taste. Smithsonian, 35(5), 24, 26. Doty, R.L. (2003). Handbook of Gustation and Olfaction. New York: Marcel Dekker, Inc. Hunter, B. (2002). How food communicates with your taste buds. Consumers Research Magazine, 85(1), 26-28. Lindemann, B. (1999). Receptor seeks ligand: On the way to cloning the molecular receptors for sweet and bitter taste. Nature Medicine, 5 (4), 381. McClure, S. T., & Lawless, H. T. (2007). A comparison of two electric taste stimulation devices, metallic taste responses and lateralization of taste. Physiology and Behaviour, 92, 658–664. Nelson, G., Chandrashekar, J., Hoon, M.A., et al (2002). An amino-acid taste receptor. Nature, 416 (6877), 199-202. Prescott, J., Johnstone, V., & Francis, J. (2004). Odour/taste interactions: Effects of different attention strategies during exposure. Chemical Senses, 29, 331–340. Silver, W. L., Roe, P., Atukorale, V., Li, W., & Xiang, B. (2008). TRP channels and chemosensation. Chemosense, 10, 1, 3–6. Sugita, M. 2006. Review. Taste perception and coding in the periphery. Cellular and Molecular Life Sciences, 63, 2000–2015. Read More