Reading Activity Week #14 (Due Monday)

The discussion I found the most interesting from Ch. 14 Taste was the basics of taste and flavor sensations. Our taste system is meant to detect nutrients and antinutrients before we ingest them. According to our book the perception of taste is actually a combination of the GUSTATORY and OLFACTORY STYSTEMS. Together it is called the RETRONASAL OLFACTORY SENSATION, the sensation of an odor that is perceived when chewing and swallowing force an odorant in the mouth up behind the palate into the nose. FLAVOR is the combination of BASIC TASTES (sweet, salty, sour, and bitter) and the retronasal olfaction. This is why when we have a stuffy nose our taste is not as good. Foods are also perceived through the SOMATOSENSORY system through touch, temperature, and pain receptors in the tongue and mouth in order to protect it and provide info about the food. The four basic tastes are currently universally accepted. SALTY is the taste quality produced by the cations of salts. Cations are positively charged ions. Saltiness is a dynamic taste and we can modify our salt preferences. SOUR is the taste quality produced by the hydrogen ions in acids. Sourness is also a dynamic preference. BITTER is the taste quality, generally considered unpleasant, produced by substances like quinine or caffeine. However, we do not distinguish between different types of bitter and avoid them because evolutionarily anything bitter was poisonous to us. Sweet and bitter tastes inhibit one another. SWEET is the taste quality produced by sugars. Our sweet receptors are tuned to three sugars that are biologically useful to us: glucose, fructose, and sucrose. GLUCOSE is the sweetest-tasting sugar and is the principal source of energy in humans. Our taste system tunes the receptors to specifically find out the biological important sugars.

The topic I found the least interesting was the anatomy and physiology of the gustatory system. Taste perception occurs through a step by step process. First, chewing breaks down the food substances into molecules which are dissolved in saliva. The molecules in the saliva then flow into TASTE BUDS, which are globular clusters of cells that have the function of creating neural signals conveyed to the brain by taste nerves. Taste buds are imbedded in the PAPILLAE the structures that give the tongue its bumpy appearance and there are also some on the roof of the mouth. There are four types of papillae and only three contain taste buds. FILIFORM PAPILLAE are the small structures on the tongue that provide most of the bumpy appearance and don’t have taste functions. FUNGIFORM PAPILLAE are mushroom-shaped structures that are distributed most densely on the edges of the tongue and taste buds are buried in the surface. FOLIATE PAPILLAE are folds of tissue containing taste buds and are located on the rear of the tongue lateral to the circumvallate papillae. CIRCUMVALLATE PAPILLAE are circular structures that form an inverted V on the rear of the tongue and are moundlike structures surrounded by a trench. Each taste bud contains TASTE RECEPTOR CELLS, cells that contain sites on their apical projections that interact with taste stimuli. Each taste bud is a cluster of elongated cells, some receptor cells end in MICROVILLI, slender projections on the tips of some taste bud cells that extend into the taste pore. A TASTANT is any stimulus that can be tasted. After leaving the taste buds through the cranial nerves, gustatory info travels through way stations in the medulla and thalamus before reaching the cortex. The INSULAR CORTEX is the primary cortical processing area for taste and first receives taste info. The ORBITOFRONTAL CORTEX is the part of the frontal lobe of the cortex receives projections from the insular cortex and integrates the information with other senses.

The first useful thing was the discussion of the pleasures of taste. Pleasure of displeasure of taste is present at birth. This is apparent in a famous study by Jacob Steiner who studied facial expressions of infants. Infants produced stereotypical expressions for each basic taste. Our basic tastes provide both information and affective experience. This allows us to solve nutritional problems without having to learn. A theory developed out of this called SPECIFIC HUNGERS THEORY, idea that deficiency of a given nutrient produces craving for that nutrient. However, it was only proven for deficiency in salt and sweet. It has been found that specific hungers don’t control all of what we eat, but our likes and dislikes of the retronasal olfactory sensations associated with foods does which is often learned.

The second useful thing was the discussion of the genetic variation in taste experience. There are considered to be three groups of genetic tasters: nontasters, tasters, and supertasters. NONTASTERS are born with two recessive alleles for the Tas2r38 gene and are unable to taste the compounds phenylthiocarbamide or propylthiouracil which are bitter in taste. TASTERS are considered to be “medium tasters” and are able to taste those compounds but weakly due to fewer fungiform papillae. A SUPERTASTER is an individual who perceives the most intense taste sensations due to a larger number of fungiform papillae.

Taste has a survival value to human. Olfactory receptors and taste receptors are meant to detect specific features of molecules. Sense of smell helps identify objects in our environment and is the primary means for knowing what surrounds us. For this reason the olfactory system can distinguish between a large number of molecules. The gustatory system on the other hand responds to a fixed small number of molecules. It helps us determine if a food is edible or harmful before we ingest it. Bitter is the body’s primary system to detect poisons. Sour allows us to know how acidic and therefore edible a food is. Sweet and salty enable us to detect and selectively ingest foods that our bodies need.

TERMS: gustatory system, olfactory system, retronasal olfactory sensation, flavor, basic tastes, somatosensory system, sweet, salty, sour, bitter, glucose, taste buds, papillae, fiiform papillae, fungiform papillae, foliate papillae, circumvallate papillae, taste receptor cells, microvilli, tastant, insular cortex, orbitofrontal cortex, specific hungers theory, nontasters, tasters, supertasters

There were a few topics in chapter 14 that I found interesting, as well as a few topics that I did not find interesting. The first thing that I thought was interesting was the brief beginning section that discusses the connection to the olfactory system and the gustatory system. The text points out that food molecules are almost always perceived by both our gustatory and our olfactory systems. the molecules that we taste are dissolved in our saliva and passed over the taste receptors on our taste buds. But when we chew and swallow foods, other molecules are released into the air inside our mouths and forced up behind the palate into the nasal cavity, where they contact the olfactory epithelium and stimulate our olfactory receptors. These retronasal olfactory sensations are then knitted together with our gustatory sensations by our brains into a kind of metasensation that goes by the name flavor. The text gives an example to help you experience this and help understand it a little better. They suggest eating a piece of chocolate with your nose plugged. Then when you go to swallow the chocolate unplug your nose. What you are supposed to experience is a lack of taste of the chocolate until you unplug your nose. Then once you are able to smell the chocolate, it will also begin to taste more like chocolate.

One thing that I did not find very interesting while reading this chapter was the discussion over coding of taste quality. In previous chapters the discussion over coding of various sections has been more interesting, this chapter, however, seemed very dull in comparison and was hard to focus on. According to the text, it is speculated that coding of taste occurs through a process known as labeled lines. This theory states that each taste neuron would unambiguously signal the presence of a certain basic taste. There is an evolutionary argument to go along with this proposed type of coding. An example of why labeled coding would have evolutionary advantages is stated in the text "Poisonous plants contain components with a variety of tastes, if bitterness were to synthesize the these other tastes, we would not be able to parse it out and thus avoid the poison.".

There are several things in this chapter which I believe are useful in understanding sensation and perception of taste. The first thing that I believe is important to understand are taste buds. taste buds are embedded in structures called papillae that cover the tongue. Taste buds are defined in the text as globular clusters of cells that have the function of creating the neural signals conveyed to the brain by taste nerves. Papillae are structures that give the tongue its bumpy appearance. From smallest to largest, the papillae types that contain taste buds are fungiform, foliate, and cicumvallate: filiform papillae, which do not contain taste buds, are the smallest and most numerous. One interesting tibbit: the filiform papillae on a cat or dogs tongue will have sharp edges, this is what allows them to drink water out of a dish, and what prevents us from being able to do this.

All of the different forms of papillae have different locations of the human tongue. The fungiform papillae are mushroom-shaped structures that are distributed most densely on the edges of the tongue, especially the tip. Taste buds(an average of 6 per papilla) are buried in the surface. These are visible to the human eye but can be made more visible by dying with blue food coloring. Foliate papillae are folds of tissue containing taste buds. Foliate papillae are located on the rear of the tongue lateral to the circumvallate papillae, where the tongue attaches to the mouth. The Cicumvallate papillae are located on the rear of the tongue and from an inverted V. They are mound-like structures surrounded by a trench. There are also taste buds that are located on the top of ones mouth. They are distributes in a line across the roof of the mouth.

Another topic that I believe is useful to understanding sensation and perception in this chapter is the brief discussion over the taste bud. According to the text, each taste bud is a cluster of elongated cells, organized much like the segments of an orange. The tips of some cells become slender microvilli(slender projections on the tips of some taste bud cells that extend into the taste pore) containing the sites that bind to taste substances. After about 10 days, taste receptors die and are replaced by new cells. This constant renewal allows the taste system to recover from a variety of sources of damage. Recordings from taste nerve fibers show that different receptor cells contacted by branches of a single fiber show similar specificity to taste stimuli. Meaning that the nerve fibers are somehow able to select the cells with which they will synapse so the message they convey remains stable even though the receptor cells are continually replaced. The mechanism that permits a taste cell to recognize a taste stimulus contacting it microvilli can be divided into two large categories. The first is made up of small, charged molecules that taste salty or sour. The second class will produce sensations that we label as sweet or bitter, are perceived via a mechanism similar to that in the olfactory system, using G-protein-coupled receptors, and is a lock and key system.

One thing that is important to remember from this chapter is the discussion over the four basic tastes. They are Salty, sour, bitter, and sweet. Salty is the taste quality produced by the cations of salts. some cations also produce other taste qualities. The purest salty taste is produced by sodium choloride, common table salt. Sour is the taste quality produced by hydrogen ion in acids. At high concentrations, acids will damage both external and internal body tissues. Bitter is generally considered unpleasant, and is produced by substances like quinine or caffeine. Also, many compounds that taste bitter, are also poisonous. However, some bitter stimuli are actually good for us. Some people are more sensitive to bitter tasting foods. Sweet is produced by some sugars, such as glucose, fructose, and sucrose These three sugars are particularly biologically useful to us and our sweet receptors are tuned to them. Some other compounds that provoke this taste are sacchairn, aspartame which are also sweet.

There have been a few studies that have discovered that not everyone tastes the same. some people can actually taste better than others. One study had participants taste crystals. Some participants said that the crystals had a bitter taste, while others said that they had no taste. All of the crystals in the experiment were the same so the only explanation for this is that some people taste differently than others. Those who did not taste anything were labeled "nontasters" while those who tasted something bitter were labeled as "tasters". Another experiment that was conducted noted that tasters could not tell the difference between an expensive wine and a cheap wine. Another study made the discovery of a group of individuals that are labeled supertasters. Those who are considered to be a supertaster experience taste at more extreme levels than those who are middle tasters, tasters, or nontasters. Also, when a blue dye is applied to the tongues of a nontaster and a supertaster, the person who is a super taster has more fungiform papillae.

Terms: olfactory system, gustatory system, retronasal olfactory sensations, flavor, labeled taste, taste buds, papillae, fungiform, foliate, circumvallate, filiform papillae, microvilli, sweet, sour, bitter, salty, the four tastes, nontasters, medium tasters, super tasters,

The sense of taste is the ability to respond to dissolved molecules and ions called tastants. Molecules released into the air inside our mouths as we chew and swallow food travel up through the retronasal passage into the nose, where they then move upward and contact the olfactory epithelium. There are fourprimary taste sensation: salty, sweet, bitter, sour. Salty - the taste qualities produced by tha cations of salt. The purest salty taste is produced by sodium chloride, common tale salt. Sour is the taste quality produced by the hydrogen ion in acid. Bitter in turn is the taste that is generally consider unpleasant, produced by substances like quinine or caffeine. And seet taste is produced by sugar such as glucose, fructose, and sucrose.
Interesting was to read about the pleasure of taste. According to Pfaffmann and his famous paper "ThePleasure of sensation" we know that the pleasure or displeasure of the taste is present at birth. Infants will like sweet and dislike bitter and strong sour.
The least interesting thing was discussion about the physiological sense of taste, yet the most useful in better understanding the function of taste, how the brain interprets the taste of the food or anyhting else.

In this chapter, i found the four basic tastes to be most interesting. Basic tastes are the four taste qualities that are generally agreed to describe the human taste experience. These include salty(the taste quality produced by the cations of salts-e.g. the sodium in sodium chloride produces that salty taste--some cations also produce other taste qualities like potassium tasting bitter and salty but the purest salty taste is common table salt)SOUR (the taste quality produced by the hydrogen ioon in acids) BITTER(the taste quality generally considered unpleasent produced by subtances like quinine or caffine) and SWEET(the taste quality produced by some sugars, such as clucose, fructose and sucrose. theses three sugars are particularly biologically useful to us, and our sweet receptors are tuned to them. ) I thought it was interesting that diets can affect are perception of saltiness. If we decrease the sodium in our diet, over time foods that we used to love that had high sodium wont taste as good because of we will perceive it as too salty. Substances that are sour get the taste by having more hydrogen ions which will make it more acidic. We find this in foods like sauerkraut and pickles along with certain candies. High concentrations of acids will damage both external and internal body tissues so we have to eat it in moderation. Most bitter tastes tend to be poisonous which may be why we dislike bitter tastes. Pregnencies distorts our perception of bitter tastes. While pregnant bitter tastes increase and later after menopause they decrease. I also found the specific hungers theory to be interesting. This theory states that deficiency of a given nutrient produces cravings for that nutrient. so if you were lacking sodium you would crave salty food. This was proved wrong for nutrients like vitamins but i found it interesting because i get the cravings for certain foods all the time and just think that they are random. However, i think that this theory makes sense.
What i found to be not so interesting in this chapter was the anatomy and physiiology of the gustatory system. Food is broken up into small molecules in your mouth and dissolved by saliva which flows to tastebuds(Globular clusters of cells taht have the function of creating the neral signals conveyed to the brain by taste nerves. Some of the cells in the taste bud have specialized sites on their apical projections that interact with taste simuli. Some of the cells form synapses with taste nerve fibers.) Taste buds are embedded in structures called papillae which cover the tongue. Papillae give the tongue the bumpy appearance. From smalledst to largest the papillae types that contain taste buds are fungiform, foliate, and circumvallate. Filiform papillae which do not contain taste buds are the smallest but most numerous.
This chapter related a lot to the previous chapter with the olfactory system. The olfactory and gustatory systems work together inorder for us to taste flavors of foods. flavor is defined by the combination of true taste which is the 4 basic tastes. retronasal olfactory sensation is the sensation of an odor that is perceived when chewing and swallowing force an odorant in the mouth up behind the palate into the nose. Such odor sensations are perceived as originating from the mouth even though the actual contact of odorant and receptor occurs at the olfactory mucosa. It also related the tongue to the retina. Each since has a control center where it interpruts the information before sending it to the brain to be examined.

four basic tastes, sweet, sour, bitter, salty, retronasal olfactory sensation, flavor, taste buds, papillae, filiform papillae, fungiform papillae, foliate papillae, circumvallate papillae, specific hungers theory

Our ability to taste is strange trait. What is the evolutionary importance of this sensation? Our tongue holds taste buds in structures called papillae, which vary in shape and are located in various areas on the tongue and mouth. A taste bud consists of a pore in the papillae and several cells with microvilli extensions. There are sites on these microvilli, or thin almost hair like sensory protrusions, that bind to specific chemicals with specific properties to create the experience of taste. Taste is what the book refers to as the information coming strictly from the receptors in the mouth and on the tongue. Flavor is the culmination of chemical messages from the tongue and olfactory experiences. We experience flavor differently than smell because the tactile sensations of chewing and swallowing act as a cue for the brain. The brain relies on cues in the mouth to discriminate between smell and taste sensations, and routes the stimuli information differently according to whether or not the cues are present. In research subjects had a nerve called the chorda tympani inhibited with lidocaine and attempted to eat various foods. The subjects found that they were able to smell the objects but not taste them. Perhaps this nerve contains or leads to the mechanism that detects cues and determines whether information should be interpreted as smell or taste sensations. Chemicals that cause taste sensations, called tastants, bind to receptors in two ways. Molecules that are charged ionically may produce a taste sensation of salty or sweet. There are openings in the microvilli receptors that allow specific chemicals through that are characteristic of sour or salty tasting stimuli. When the charged molecules enter the cell they create a difference in charge between the inside of the cell and the outside. This difference in charge allows the cell to fire an action potential to the cranial nerve fiber. Tastants containing molecules that are not ionically charged, meaning they are bound with stable covalent bonds, are detected with a G-protein receptor and produce sweet and bitter taste sensations. G-protein receptors are geometrically driven. When a molecule with a key feature, such as an active group, it binds to a receptor shaped specifically for that molecule. Then G-protein associated with the receptor than signals channels to allow positively charged calcium ions to flood into the cell, again causing the activation threshold, or difference in charge, needed for an action potential.

Adaption happens in taste just like every other sensory system. We are constantly adapted to the salt and acid in our saliva and a very salty dish tastes less salty by the last bite. Cross adaption in when we experience a taste sensation in excess because another type of taste sensation has caused adaptation, and the sudden change is perceived differently, and sometimes as unpleasant, like orange juice after eating something sweet.

Super-tasters have been studied using interesting methods. Modality matching refers to humans ability to be able to match the intensities of two stimuli, such as the brightness of a light and the volume of a sound. Super-tasters show a much higher ability to detect the intensities of tastes and match them to a similar ratio of level of intensity of sounds.

The specific hungers theory holds that taste allows us to recognize food and its basic nutritional value, and that we experience cravings for the taste of foods containing nutrients that we are in need of. This system of craving supposedly keeps the body in balance with the nutrients it consumes, although there is much vulnerability to behavioral influences. Associations between particular tastes and smells and unpleasant experiences can be formed. For example when I was a child for dinner one night I had eaten biscuits and gravy. I caught the flu and got sick a couple hours later, and puked up the whole meal. For years the thought of the taste of biscuits and gravy, even the smell made me queasy and gag. Perhaps taste is supposed to be so susceptible to behavioral association, evolutionarily speaking. If you eat something that prolongs your life and improves your health you like the taste of it, and associate that food with well being.

Most of the information in this chapter was interesting to me, the one exception was on genetic variation in taste experience. This section discusses that for the compound PTC some are able to taste it and some are not. For those who can they receive a bitter taste. Researchers found that the ability to taste this compound was due to genetics. Nontasters have two recessive alleles on the Ta2r38 gene while tasters have one or two dominant alleles.

One of my favorite sections was on specific hungers. The specific hungers theory stated that when the body needed nutrients our body would crave food that contained it. After satisfying our craving our body would again be in balance and the craving would go away. There was originally a lot of support for this theory however it was later found that this is limited only to sweet and salty. The idea is that the saltiness of salt and the sweetness of sugars work as cues for our body but those cues do not exist for other substances. This section also discusses our likes and dislikes of foods. The chapter states that much of what we like and dislike is connected to the retronasal olfactory sensation.

One of the most useful parts of this chapter was the very beginning when they discussed taste vs flavor. The chapter explains that food molecules are perceived not only by our gustatory system but also our olfactory system. When we chew and swallow food there are molecules released into the air in our mouths. This is then forced up into the nasal cavity and they contact the olfactory epithelium and it stimulates our olfactory receptors. Flavor is the name given to the retronasal olfactory sensations mixed with our gustatory sensations.

The next useful portion of the chapter was on the anatomy and physiology of the gustatory systems. Just as with all the other senses the perception of taste can be broken down into a series of events. The first step is chewing which breaks down the food in molecules so it can be dissolved in saliva. The "saliva-borne food molecules" then flow to a taste pore which leads to the taste buds. The taste buds are embedded in papillae which covers the tongue. The taste buds contain taste receptor cells. The taste receptor cells wend information to the cranial nerves in the brain. This is the basic rundown of the information however as with the other senses it's a little more complex so I'll break it down.

The tongue is covered in one of 4 types of papillae. Filiform papillae is the only one of the 4 that does not have taste buds. The filiform papillae cover the tip of our tongue (anterior). Along with the filiform papillae the fungiform papillae also are on the tip of our tongue. Each of the fungiform papillae contains about 6 taste buds. One the sides of our tongue we have foliate papillae which also contain taste buds. Lastly there is the circumvallate papillae. These are located on the rear of the tongue in an inverted V shape, again these papillae have taste buds.

Taste buds are located not only on our tongues but
also on the roof of our mouths. Taste buds each consist of a group of cells that looks like the segments in an orange. At the top of the taste bud is the taste pore which is where the molecules enter the taste bud. The first thing they will encounter is the microvilla which are on the tips of some of the taste receptor cells. The microvilla contains the sites that bind to the taste substances. As I mentioned the microvilla are connected to the taste receptor cells. The taste receptor cells respond to only a limited number of molecule types. Taste receptor cells die after about 10 days and are then replaced by new cells. Some of the taste receptor cells interact with taste nerve fibers and others do not. However all of them are able to convey the information to the nerve fibers. Taste cells are able to recognize specific taste stimulus known as tastant. There are two categories of tastants the first is made of small, charged molecules that are salty or sour and the others are perceived as sweet or bitter.
The information from the taste molecules aren't done when they hit the taste nerve fibers. Once their they travel through the medulla and thalamus and then reach the cortex. Once in the cortex the information first goes to the insular cortex. This is the primary area that processes the information. Next the information goes to the orbitofrontal cortex which has neurons that are multimodal in that they not only respond to taste but also to temperature touch and smell. The fact that the area is multimodal suggests that it could be an integration area.

It's also important to talk about the 4 basic tastes. These are salty, sweet, sour and bitter.

Salts are made of 2 charged particles: a cation (positively charged) and a anion (negatively charged). The next of the basic tastes is sour. When we perceive something to be sour it is due to "the hydrogen ions in acids". Next is bitter. The human genome project was able to find a multigene family that is responsible for about 25 different bitter receptors. Generally we do not distinguish between the tastes of the different bitter compounds. Often things that taste bitter are poisonous but some are good for us. Some examples of things that taste bitter are quinine (which is in tonic water) and caffeine. The ability to perceive bitterness in woman is affected by hormone levels. During pregnancy the the perception of bitterness is amplified and it is diminished after menopause. The last of the basic tastes is sweet. The ability to perceive sweetness is due to sugars. Our taste receptors that are stimulated by sweetness are tuned to perceive the sweetness in some sugars but not others. Primarily they are glucose, fructose, and sucrose which are all useful to our bodies.

Terms: alleles, specific hungers theory, taste, flavor, gustatory system, olfactory system, olfactory epithelium, olfactory receptors, saliva, taste pore, taste bud, papillae (filiform, fungiform, circumvallate, foliate), taste receptor cells, cranial nerves, microvilla, taste nerve fibers, tastant, medulla, thalamus, cortex (insular, orbitofrontal), salty, sweet, bitter, sour

What I found most interesting was the four basic tastes, basically because I love food and wanted to know why it is that we like certain foods on a given day. The basic tastes are four taste qualities that are generally agreed to describe human taste experience: sweet, salty, sour, and bitter. Salty is the taste quality produced by the cations of salts (e.g., the sodium in sodium chloride produces the salty taste). Some cations also produce other taste qualities (e.g., potassium tastes bitter as well as salty). The purest salty taste is produced by sodium chloride (NaCl), common table salt. Sour is the taste quality produced by the hydrogen ion in acids. As the hydrogen ions increase the solution becomes more acidic. Bitter is the taste quality, generally considered unpleasant, produced by substances like quinine or caffeine. Sweet is the taste quality produced by some sugars, such as glucose, fructose, and sucrose. These three sugars are particularly biologically useful to us, and our sweet receptors are tuned to them. There are some other compounds like (e.g., saccharin, aspartame), that are also sweet.

Taste and olfaction play very different roles in the perception of foods and beverages. Taste is the true nutritional sense; taste receptors are tuned to molecules that function as important nutrients. Bitter taste is a poison detection system. Sweet taste enables us to respond to the sugars that are biologically useful to us: sucrose, glucose, and fructose. Salty taste enables us to identify sodium, a mineral crucial to survival because of its role in nerve conduction and muscle function. Sour taste permits us to avoid acids in concentrations that might injure tissue.

What I found least interesting was the anatomy and physiology of the Gustatory System, basically because I’m not a fan of anatomy. Taste buds are globular clusters of cells (like the segments in an orange). The tips of some of the cells (microvilli) contain sites that interact with taste molecules. Those sites fall into two groups: ion channels that mediate responses to salts and acids, and G protein–coupled receptors that bind to sweet and bitter compounds.
The tongue has a bumpy appearance because of structures called papillae. The filiform papillae (most numerous) have no taste buds. Taste buds are found in the fungiform papillae (front of the tongue), foliate papillae (rear edges of the tongue) and circumvallate papillae (rear center of the tongue), as well as on the roof of the mouth. Taste projects ipsilaterally from the tongue to the medulla, thalamus, and cortex. It projects first to the insula in the cortex, and from there to the orbitofrontal cortex, an area where taste can be integrated with other sensory input (e.g., retronasal olfaction). Furthermore the taste buds are embedded in the papillae that cover the tongue. Each taste bud, contains a number of taste receptor cells which are cells within the taste bud that contain sites on their apical projections that can interact with taste stimuli. These sites fall into two major categories: those interacting with charged particles (e.g., sodium and hydrogen ions), and those interacting with specific chemical structures. Each taste receptor cell responds to a limited number of molecule types; when one of its preferred molecules make contact with it, it produces action potentials that send information along one of he cranial nerves to the brain. Furthermore with the papillae there are four major varieties, three of which contain taste buds these are (1) filiform papillae: Small structures on the tongue that provide most of the bumpy appearance. Filiform papillae have no taste function. (2) fungiform papillae: Mushroom-shaped structures (maximum diameter 1 millimeter) that are distributed most densely on the edges of the tongue, especially the tip. Taste buds (an average of six per papilla) are buried in the surface. (3) foliate papillae: Folds of tissue containing taste buds. Foliate papillae are located on the rear of the tongue lateral to the circumvallate papillae, where the tongue attaches to the mouth. Finally there is circumvallate papillae: Circular structures that form an inverted V on the rear of the tongue (three to five on each side). Circumvallate papillae are moundlike structures surrounded by a trench (like a moat). These papillae are much larger than fungiform papillae. Moreover, when it comes to taste buds and taste receptor cells there is a thing called microvilli which is slender projections on the tips of some taste bud cells that extend into the taste pore. Taste nerve fibers that enter the taste buds branch so that an individual cell can be innervated by more than one taste fiber and an individual taste fiber can innervate more than one cell. Tasate recepots have a limited life span. In addition, the mechanisms that permit a taste cell to recognize a taste stimulus, known as a tastant, contacting its microvilli can be divided into two large categories. One class of tastants is made up of small, charged molecules that taste salty or sour. Tastants in the second class, which produce sensations that we label as sweet or bitter, are perceived via a mechanism similar to that in the olfactory system, using G protein-coupled receptors. When it comes to taste processing in the central nervous system…the primary cortical processing area for taste—the part of the cortex that first receives taste information—is the insular cortex. Orbitofrontal cortex receives projections from the insular cortex. It is the part of the frontal lobe of the cortex that lies above the bone (orbit) containing the eyes. Inhibition plays an important role in the processing of taste information in the brain. One of the functions of this inhibition may be to protect our whole-mouth perception of taste in the face of injuries to the taste system.

Three things that I read that I found most useful for understanding sensation and perception is taste, taste buds, papillae

Other chapters that relate to this chapter on taste include: The olfactory and gustatory systems work together in order for us to taste flavors of foods. Flavor is defined by the combination of true taste which is the 4 basic tastes. Also everything in the chapter results back to the brain, our pleasure center or what we like and dislike from what we taste/encounter.

Key Terms: Basic tastes, bitter, circumvallate papillae, filiform papillae, flavor, foliate papillae, fungiform papillae, insular cortex, microvilli, orbitofrontal cortex, papillae, retonasal olfactory sensation, salty, sour, sweet, tastant, taste buds, taste receptor cells.

The aspects that I found most interesting in this chapter were the gustatory system. The gustatory system is interesting because it talks about the tongue, which is the strongest muscle in the body. We will start with the taste buds. Taste buds are globular clusters of cells that have the function of creating the neural signals conveyed to the brain by taste nerves. Some of the cells in the taste bud have specialized sites on their apical projections that interact with taste stimuli. Some of the cells form synapses with taste nerve fibers. Within the taste buds are papillae. Papillae are structures that give the tongue its bumpy appearance. From smallest to largest, the papillae types that contain taste buds are fungiform, foliate, and circumvallate; filiform papillae, which do not contain taste buds, are the smallest and most numerous. The papillae come in four major varieties. The varieties are filiform papillae, fungiform papillae, foliate papillae and circumvallate papillae. Filiform papillae are small structures on the tongue that provide most of the bumpy appearance. Filiform papillae have no taste function. The fungiform papillae are Mushroom-shaped structures that are distributed most densely on the edges of the tongue, especially the tip. They can be up to a diameter of one millimeter. Taste buds are buried in the surface. There is an average of six taste buds per papilla. The third variety of papillae is foliate papillae. Foliate papillae are folds of tissue containing taste buds. Foliate papillae are located on the rear of the tongue lateral to the circumvallate papillae, where the tongue attaches to the mouth. Last but not least are the circumvallate papillae. Circumvallate papillae are circular structures that form an inverted V on the rear of the tongue. There are three to five on each side. Circumvallate papillae are mound like structures surrounded by a trench. These papillae are much larger than fungiform papillae. As a complete package the taste buds are distributed in a line across the roof of the mouth and in papillae distributed in an oval on the tongue. Fungiform papillae make up the front of the oval, and foliate and circumvallate papillae make up its rear.

I feel the least interesting would be the specific hunger theory. I think it is all mind over matter. The specific hunger theory is the idea that deficiency of a given nutrient produces craving for that nutrient. The craving is for a specific taste. Curt Richter first proposed this idea and demonstrated that cravings for salty or for sweet are associated with deficiencies in those substances. However, the idea proved wrong for other nutrients like vitamins and such.

Three things I read about in chapter 14 that I think will be the most useful for me in understanding sensation and perception are the gustatory system, the pleasure of taste and the process in the central nervous system from your taste buds. I know that the magic school bus is a cartoon but you can learn a lot from their trip into different areas of the body. All three go together. One cannot function really without the other. The brain is a huge part of our sensation and perception. I would say knowing what the function of the brain is is the most important part of each chapter I read. Like in taste the insular cortex is the primary cortical processing area for taste it is the part of the cortex that first receives taste information.

The part the brain plays in all the different roles of sensation and perception would have to include the whole book.

TERMS: gustatory system, taste buds, globular clusters of cells , synapses, nerve fibers, papillae, filiform papillae, fungiform papillae, foliate papillae and circumvallate papillae, specific hunger theory, Curt Richter , process in the central nervous system