After reading the attachment I sent out and reading what your text says about the sense of smell - please answer the following questions.
What does your text say about odor and the sense of smell?
What does the article say about odor the sense of smell?
This Stereochemical Theory of Odor (J., Amoore, J., Johnston, & M., Rubin, 1964). summarizes the search for an understanding within the science of osmics, which means smell. The author discusses how little science has understood this complex sensory experience, and how so far, science has failed to validate the existing theories. However, with a return to an ancient theory put forth by Lucretius, who said that smell happened by the way the size and shapes of our minute pores matched up with the odor given off by a particular substance. Using this theory with an understanding of the way our neurons transport and process information, the researchers in the present study were able to develop, test, and prove a theory that explains how our smell sense differentiates and distinguishes between different types of smell.
The discovery of this study is that, as theorized, the primary way in which our neural receptor sites recognize smell is through the shape of the compounds take on depending on their molecular construction – which could be altered by the researchers in order to test the theory on human subjects. Simple alterations in the shape of the molecule drastically changed the way human subjects reported what they were smelling in the study. And so, like Lucretius thought long ago, the shape and size makes a match that we recognize to distinguish between various substances.
The Goldstein text supports the theories in the Amoore et al article, and expands on this theory with modern verbiage, and current physiological understanding developed through studies done since the time of the aforementioned article.
Some of these current understandings include the way the activated receptor neurons detect smell through a “recognition profile” – this is the activation profile for each oderant. This profile was discovered through a new technology called calcium imaging. Calcium imaging measures the concentration of calcium ions in individual receptors.
Additionally, the technology of optical imaging which measures brain activation (and reserved for lab animals due to the invasive nature of this technique) has shown how compounds activate different areas and positions in the olfactory bulb based on the functional group and the length of the chain for that compound.
The portion of the textbook dealing with olfaction concludes by explaining that our olfactory system can detect a nearly limitless number of odorant types due to its ability to code the compounds in these ways.
1) The text book states that odor is a general smell sensation of a particular quality. When we are referring to the specific chemical entity however, we use the term "odorant". It goes into detail about exactly how we preceive smells through our noses. It directs odarants into the olfactory epithelium which is where smells are detected. The text also talks about Anosmia which is the inability to smell. This is most often the results from sinus infections, or head trauma. There are also specific anosmia which is the inability to smell one specific compound when an individula has otherwise normal smell perception.I thought it was interesting to read all the information on smell because I never realized how much it takes just for our senses to occur and all the different places and things that work together in order to just recognize smell and smell all the different kinds of smells and odors. The book discusses theories of Olfactory Perception and how shape-pattern theory condtends that odorant molecules have different shapes and olfactory receptors have different shapes and odorants are detected by specific Olfactory receptors. The text discusses how we detect odorant mixtures by using analysis and synthesis. An example of analysis is auditory mixtures while color mixtures are an example of synthesis. The book also talks about how although we are able to imagine images, we are not however able to produce odor imagery. The example they use is that we are easily able to picture a chocolate kiss in our heads, however, we are not able to imagined the exact smell or oder of this chocolate kiss. However, with training, it is possible for some to create sensory representations of smells, which perfumers and chefs often say they are able to image olfactorily. I thought it was interesting how they talked about "Tip of the tongue" Phenomenon, and similar to this is "Tip of the nose" phenomenon, which is the exact same, only dealing with smells and odors instead of words.
2) I liked how this article started off comparing roses to skunks. This is funny to me because I happen to like the smell of skunks which usually grosses everybody else out. So, this was funny to me. The article starts off talking about how sense of smell is a chemical sense and how the nose is constantly detected and looking for different odors. The article also describes how odors and smells come to be. This involves warm air traveling to the olfactory receptors and nerves which then send signals to the olfactory bulb and to the higher brain centers. These signals are then integrated and interpreted in terms of the character and intensity of the odor. In this article there is a table that has examples of primary odors, chemical examples of these odors and familiar substances for the odors. An example would be the smell of peppermint, the chemical would be menthone and a familiar substance would be mint candy. There are rules that all materials must have certain basic properties. The first property is that it must be volatile. The second rule says that in order for an odorous substance is that it must also be soluble in water and soluble in lipids or fatty substances. I thought this article was interesting because it showed diagrams and drawings of how air travels through our noses to the olfactory bulb and then to the brain where it is then detected as a certain odor or smell. The diagram made it a little easier to follow and understand the exact process, whereas the book used a lot of big difficult words to describe this process.
My text gives four main facts about human olfaction. 1. Although humans are less sensitive to odors than other animals, our olfactory receptors are very sensitive. 2. Humans are surprisingly good at detecting differences in odor intensity. 3. The olfactory system is excellent at identifying odors. 4. Human olfaction has the potential to provide information about other people. The text then goes on to explain how the olfaction system works. I found it interesting that the olfactory system sends signals not only to the brain for smell sensations but to the areas of the brain for memory and emotion. I had never really though about this but it’s true. Every once in a while I will smell a certain kind of perfume that reminds me of my great grandma who passed away when I was in high school. That leaves me thinking about her all from the small of a ladies perfume. The text also goes on to discuss odor quality, and how odor effects taste. When we smell something the stimuli goes in our nose to the olfactory mucosa that triggers receptor that then goes to the olfactory bulb then to the olfactory cortex and the orbitofrontal cortex in our brains.
This article describes how the olfactory system works in a different kind of way. They explain that certain smells have molecules that form different shapes. This is then how our brain can tell what we smell. The article also discussed a theory by R. W. Moncrieff. He hypothesized that everyone has different receptor cells that represent a different distinct odor. They gave the example of a lock and key. Only a certain kind or odor would receive a certain kind of stimulus. Research later determined seven different distinct odors. Then the shapes of these seven odors had to be determined. I thought this was very interesting. After reading about the man who tasted shapes this brings a whole new meaning to his condition. In reality we are all smelling shapes. It’s just on a molecular level.
1) My text first talks about the sense of smell as a chemical sense because the receptor cells for smell and taste are both sensitive to chemical stimulation. The basic stimulus for smell is a molecule of a volatile substance that moves through the air to our receptors. The range of these molecules is so extensive that humans are able to tell the difference between 500,000 odors. Smelling is also known as olfaction and smell maybe be closely linked with emotion. I know for me when I smell something it can trigger a memory and that can be very powerful all from a smell. My book mentions Amoore and how he proposed a different classification system. Most systems emphasized perceivers’ reactions to odors, whereas Ammore’s system focuses on the chemical structure of the odors. According to Ammore’s stereochemical theory, odorous molecules have definite shapes that determine the kind of odor we smell. He initially suggested that we have 7 primary odors, but later he expanded the total number of human primary odors to 32. We have olfactory receptors that seem to respond to millions of different chemicals and we can identify around 10,000 different odors. Although, we are thought to be able to discriminate between 500,000 different odors our identification of these odors is limited. People are fairly accurate in identifying everyday odors such as popcorn, coffee, paint, bananas and chocolate, but people made more mistakes while identifying unfamiliar smells. Females are somewhat more sensitive than males to various odors and females are more accurate on odor identification tasks.
2) Ammore’s article started off with difference between the smell of a skunk and a rose, we can easily tell the difference between the smell of a skunk and a rose, but we can’t describe and explain this difference. He describes how we don’t have a way of measuring smell and there hasn’t been much research done regarding smell and what makes two odors different. Ammore’s primary goal of this study was to answer these two questions 1) what are the primary odors? 2) What is the shape of the receptor site for each one? To find the answers to these questions they looked for clues in the chemical characteristics of odors. He found that there were seven primary odors and found the correct size, shape, and chemical affinities of the seven corresponding receptor sites. He came up with the Stereochemical theory which states that odorous molecules have definite shapes that determine the kind of odor we smell. Ammore’s article about smell is very interesting. His research was found in my textbook and described the 7 primary odors that he pointed out in this study.
The textbook talks about some facts that show that our powers of olfaction are greater than we might think; first is that our olfactory receptors are extremely sensitive. Second, we are surprisingly good at detecting differences in odor intensity, and the olfactory system is excellent at identifying odors. The stimuli for smell are molecules in the air, so if we smell a flower we are sensing molecules that have left the flower and have traveled through the air to our nose. The text also talks about Henning’s odor prism. His six corners consist of putrid, ethereal, resinous, spicy, fragrant, and burned are located. However, this prism is now of only historical importance. A more modern approach to odor quality is a technique, odor profiling. This is when observers rate the components in odors by comparing them to reference standards.
The article starts off by talking about the basic properties of a scent. First it must be volatile. The article uses the example of onion soup because it is really odorous because it keeps giving off vapor that can reach the nose. The second requirement is it should be soluble in water. The third requirement is solubility in fatty substances which allows it to penetrate the nerve endings through the lipid layer. Shifting the position of a group of atoms may sharply change the odor of the compound. This led chemists to think that the primary factor determining the order of a substance might be the overall geometric shape of the molecule. Primary odors are easier to pick up on, these primary odors are camphoraceous, musky, floral, peppermint, ethereal, pungent, and putrid.
I work in fragrances and what I’ve noticed and what I’ve learned is that certain people like certain fragrances. If I point out a certain fragrance that I like to someone and they don’t like it, I’ll then show them a fragrance that I don’t like and a lot of the times they end up liking that one. I also know that there are three types of fragrances based on their intensity and how long the scent will last. Based on this article, even though these fragrances have the same smell, they must have different molecule structures because the intensity of the smell is different. Last thing I know about fragrances is that they are made up of “notes” which are the different scents like vanilla. These notes change the longer you wear the perfume. The light notes are what you first smell and then the medium notes and then the high notes. It’s amazing that the smell of the perfume can change like that based on the time that it is out of the bottle. Maybe it changes because of its interaction with our skin and our pheromones.
My text begins by describing smell as a chemical stimulus. For a substance to be smelled, it must be volatile and be able to pass into a gaseous state. My text says that chemicals excite olfactory receptors to arouse a particular odor. Also, my text says that scent depends on the receptors and not the specific chemicals. Sensitivity of smell is discussed in my text. The olfactory system is very sensitive to extremely small amounts of odors and is said to be the most sensitive of the chemical senses. Differences have been found in gender and age for odor sensitivity. Females are more sensitive, for example, to a musk-like smell. Overall, women have been shown to outperform men on odor detection. Sensitivity to odors also decreases with age. Also, smokers at all ages were not shown to be as sensitive to smells as non-smokers.
My text briefly talks about adaptation to smells. Most people have realized that there is an adaptation to smells. For example, you may not notice your perfume/cologne after a few hours but others do. Another topic covered is the connection to memories that certain scents can have. Most of us have also had a personal realization of this. Maybe you’ve smelled a certain detergent that reminded you of helping with laundry when you were younger. Or maybe a certain smell, like tulips, reminds you of the warmer months of the year.
My text does not focus on how smells are sorted out by our receptors but just says that there seems to be some sort of pattern.
The article, “The Stereochemical Theory of Odor,” goes into detail about how we detect and identify odors. This article says that the shape of the molecules is the main determinate of odors. We detect molecules with fibers in an olfactory cell. My text gave a similar explanation but was not as easy to understand. This article says that we have different receptor cells that will allow the different shapes of the odor molecules to fit into. There are seven primary odors in which all other odors can be produced from combining. These can be compared to the primary colors which can be combined to create any other colors.
This theory was tested using humans. The results showed that the change in odor is due to the change in the shape of the odor molecule. This theory was also tested using honeybees. These results showed that they were able to distinguish between scents from different primary odors. They finally tested this theory using frogs. Frogs were found to have about eight odor receptors with five of them being similar to the human seven.
I liked this article. It brought a lot of information that my text did not provide such as the seven odor receptors. This is a very interesting topic. I hope we get to read more about smell and maybe taste before the class ends.
1) It worked out nice because my text had a specific couple pages about how humans are surprisingly good at detecting differences in odor intensity. Saying that the smallest difference in intensity between to stimuli that can be detected comes down to the difference in threshold. An experiment that has been down was taking two different cotton balls with different odors and asking people to rate the intensity of the odor. What they found was that the odor needs to be between 25 to 33 percent for someone to start to pick up the odor. Anywhere below those numbers and a majority of people will not be able to pick up the smell. This just goes a long with the article that we had to read talking about how different people catch different smells. They used the lock and key example assuming that everyone smelled the same for the same subjects, this just shows that what some people might smell others might not have even picked up the smell yet. The text also talks about the importance of the olfactory system and its importance on identifying different odors. It talked about the different types of experiments people have done to try and get people to remember different odors. Showing the importance of odor and our memory. One of the studies said we could ask our friend to bring out something and have us identify it by its smell, and a majority of people would be able to because they have been around that person long enough and been able to associate that smell with that person. It goes along with how my dad used to wear brute, I will still always think of him when I smell that but it has been years since he has used it. (thank the lord) This article talked about the importance of odor and different studies that have shown how its important and the text book was able to back up a lot of the information that the article was trying to summarize. Odor is something that is very important to us and it shows with the ways we are able to remember certain things.
2) The article starts off talking about the different types of smells a person smells. Saying its hard to gain a lot of information about smell because we are not able to rate its strength. Its important to understand that some smells are worse than others but its not like you are able to get out a yard stick and just measure the strength of a certain smell. The way a person smells is actually a chemical sense and the nose is always out trying to detect different odors. I have heard that our best link to memory is through our sense of smell, which I think is fascinating. Basically saying that the cologne Brute will always remind me of my dad from when I was little, even though he doesn't wear that same stuff today. Its important to understand how smell comes to us, the article says that warm air hits out olfactory receptors and nerves which sends a signal to our olfactory bulb and than to the brain. The odors are then picked out and we understand if it is a bad or good smell, and also judges the different intensity. The chart in the article talks about different smells that people are able to pick up, saying that there are primary odors, chemical, and familiar. For example the primary odor could be something floral which than would be the chemical smell of phenyl ethyl methyl ethyl carbinol which for our familiar substance is roses. It just shows the different ways people are able to describe the sense of smell and the different types of impacts it could have on us. R.W. Moncrieff was one of the first people to say that all peoples receptor cells are different and some cells represent a different odor. They use the example of a lock and key saying that a certain object releases a distinct odor, while later research has shown that there are seven different odors for this example. It just shows how much more research can be done to try and show the importance of smell, its something that many people take for granted.
1) My textbook starts off by saying humans often take their sense of smell for granted. Human’s often underestimate their olfactory receptors because they are not as sensitive as some animals. Dogs are 300 to 10,000 times more sensitive to odors than humans. Our nose and brain are remarkably good at distinguishing odors however, and then saving this as a memory to recall later if we should ever need to. Problems arise not in our identification of a scent, but in the retrieval of this memory. The human nose is very good at distinguishing the difference in odor intensity. Our average difference threshold is around 19%. Our sense of smell might work in our interpersonal relationships as well. The study done with males wearing t-shirts and females rating attractiveness based on the smell of the sweat is an example of this. My textbook also discusses that the syncing of females who live in close quarters or are around each other often may also be an example. I thought this was interesting because scent often times does play a role in our relationships. We often times remember someone based on their perfume or cologne or associate particular smells with someone. For example, friends who consistently wear the same type of perfume “become” that perfume. No one else wears it because everyone associates that odor with a particular person. Another example is that scents becoming comforting based on their associations with a person. I know many girlfriends are comforted by the scent of their boyfriend, and that is part of the appeal of wearing their boyfriend’s sweatshirts etc. One part I thought was interesting in my textbook is that we have trouble classifying odors. My textbook gives the example that if we were asked to smell B-ionone we would say it smells like violets. However, when given real violets and this chemical we would say they smell different. Our sense of smell generalizes odors. One such way that odors are categorized is using Henning’s odor prism. Henning’s prism includes the following qualities: putrid, ethereal, resinous, spicy, fragrant, and burned. Odors will fall somewhere between these qualities. For example, the scent of a lemon has both ethereal and resinous properties but resides closer to the ethereal corner.
2) The article begins by discussing how keen our nose is at distinguishing different odors. We can tell the difference between a skunk and a rose instantly. The article discusses the elementary properties of odorous materials which include: soluble in water, stimulation olfactory nerve endings, and solubility in lipids. Strong odors, according to the article, are often times associated with chains of 4 to 8 carbon atoms. By changing the chemical makeup of an odor, it can become pungent or putrid to the nose. The article discusses the smell of peppermint which is easily recognizable to most, and how changing the makeup of the molecules changes the smell to our olfactory receptors. Ammore found there were 7 primary odors, and corresponding receptor sites in our olfactory senses. The seven main odors include: camphoraceous, musky, floral, peppermint, ethereal, pungent, and putrid
1.) My book starts talking about the sense of smell through an example of the dog sniffing the ground to pick up scents. The author talks about the amazing sense of smell the dog has and why that causes people, mostly criminals, to fear dogs so. The author then begins to talk about the human’s sense of smell and how that signals something for us to understand. An example would be if a human smells a terrible smell, they automatically think of where the source could be, like the leftovers in the trash can from supper three nights ago. Smells signal humans to a series of memories or previous episodes to help us locate and understand smells. He also says that our understanding of certain smell is highly correlated to our emotions. For example, if we smell cinnamon, our memories may take us back to when grandma was still alive and made us cinnamon cookies and therefore we have a happy emotion tied to the scent of cinnamon. Another interesting point the author talks about is how humans can develop a “continued taste aversion” to certain foods that we smell. If we have a bad experience with that food, we avoid the smell (and food) all together. A process that goes into our ability to smell is odorants. Odorants are molecules in the items that allow it to be able to be smelled. One main theory the author talks about in this section is called the Lock-and-Key Theory. The Lock-and-Key Theory is when specific proteins in the cell walls of the cilia form reverse chemical bonds with specific parts of particular odorant molecule. Anosmia is when a person has“odor blindness” to certain substances.
2.) The article talks about how the nose is always on the “lookout” for possible smells. The constant air drawn from the nostrils is filtered as it passes three baffle-shaped bones in the upper part of the nose. The tissue in our noses has embedded nerve fibers that detect the odors. Our nose is very good at detecting different smells. A big point in the article talks about how the nose detects strong odors compared to small ones. After the nose detects a “strong” smell it is then associated with four to eight carbon atoms. Compared to animals, humans have a harder time detecting the strength of a smell just by scent. They may smell the smell, but to understand the harshness of the smell they struggle. One example that really stood out to be that the author of the article uses is the sense of smell when smelling onion soup. The strength of the onions is an ongoing smell therefore the nose continues to smell is over and over and that smell can be overpowering which may cause us to tear up when we smell onions. This may also be why so many people dislike onions. The smell of the onion causes us to tear up and therefore we develop a “continued taste aversion” to the onions.
My text starts off by stating that our sense of smell enables us to detect extremely low concentrations of some odorants. The detection threshold for odors is the lowest concentration an odorant can be detected. Our sense of smell is much less sensitive than many animals. Rats are 8-50 times more sensitive to odors than humans and dogs are 300-10,000 times sensitive depending on the odorant. The concentration of an odorant has to be increased by as much as factor of 3 above the threshold concentration before the person can recognize the odors quality (called recognition threshold).
An interesting fact the book stated is that even though we can discriminate between as many as 100,000 different odors, we often find it difficult to accurately identify specific odors. I had to keep reading to see what was so interesting about this obvious fact. When people are presented with different odors (bananas, coffee, motor oil) they can easily tell the difference between them. When asked to identify the substance associated with the odor, they are successful only about half of the time.
Our nose is constantly sensing odors. Odors have different strengths of smell, so we can obviously tell the difference between a skunk and a rose odor.
However we are not able to describe and/or explain this difference. There is no way to measure the smell, so the research behind odor is very limited. There are basic properties of odorus materials: It must be volatile and must be soluble in water. Beyond the elementary properties, it becomes vague and confusing.
A few general principles were discovered by chemists: One was found that adding a branch to a straight chain of carbon atoms in a perfume molecule increased the potency of the perfume. Another is that when shifting the position of a small 6 carbon atom ring it can drastically change the odor of the compound; on a ring of 14-19 atoms, they can be rearranged in any order without altering the odor much.
My text emphasized how astounding our sense of smell is. We are actually able to detect up to 10,000 different odors and we use these for a variety of different tasks, such as deciding who not to sit next to on a bus, which clothes are dirty, what food is alright to eat, or just to enjoy the different aromas present in our lives. When we smell, the air goes up through our nose and up to the olfactory epithelium, which is a little sheet of tissue about the size of a postage stamp. Each receptor has a little pocket that is just the right shape to hold either a molecule or a group of similar molecules. When these molecules fit into this pocket, an electrical signal is sent to the olfactory bulb in the brain which converts this signal into an odor. Many people experience smell loss, usually either because of age or illness. Although this is not as devastating as the loss of some other senses, like sight or hearing, it still can be detrimental to a person’s quality of life. Total smell loss is called Anosmia, and it affects about 1-2% of the population. As people age, their sense of smell usually tends to worsen, but does not usually result in complete Anosmia. People who have any sort of smell impairments often have problems with safety, eating, or insecurity because they cannot detect their own body odors. A common view on why we have different preferences toward smell is that our preference is learned. Smell is based largely on memory, and we often like or dislike certain odors based on our emotional responses that we make when we encounter them. These associations can start developing very early on in life and often vary from culture to culture.
This article starts out discussing the difficulty that we have in describing smells, except to describe them as something that they smell similar to. Thousands of years ago, a poet named Lucretius described smell as being the identification of molecules of different shapes and sizes that fit into different pores. Although it is now described a little differently, that is basically how the stereochemical theory works. Stereochemistry is the study of atoms and molecules and how they are arranged. Inside your nose there are little patches of tissue that contain nerve fibers. These fibers detect odor and send these signals to other parts of the olfactory system which in turn send these messages to the brain. For us to smell things, certain characteristics must be present. First, the smell must be volatile and create vapors that are released into the air for your nose to smell. An odor from a substance must also be water soluble. An odor can vary in potency, and by adding, taking away from, or rearranging the molecules that make up a scent, potency as well as odor can be changed. Chemists have found that there are seven primary odors, which all smells are made of, similar to how there are primary colors that then make up all the different colors. These seven odors are camphoraceous, musky, floral, pepperminty, ethereal, pungent, and putrid. Each primary odor has a uniquely shaped olfactory receptor. Sometimes molecules can fit into more than one receptor, depending on which way they go in, and these odors result in a compound smell. This theory is able to identify odors without using the olfactory system, but just by examining the shape of its molecules and has been tested and retested with accurate, consistent results not only with humans, but also with bees.
Online I found some additional facts about our sense of smell (http://www.senseofsmell.org/)
- Everyone has their own unique odor-identity or “smell fingerprint”
- No two people smell the same odor the same way
- A woman’s sense of smell is keener than a man’s
-People recall smells with a 65% accuracy after a year, but visual recall of photos is only about 50% after 3 months
- A dog has about a million cells that detect odor per nostril, and these cells are 100 times larger than humans
According to the text by Goldstein (2007) it states that the sense of Smell is also called the Olfactory system is one of the gatekeeper of the body. It identifies the identify of what we are going to consume and identify when things are bad so we reject it. Smell can also cue memories that were either good or bad. If the smell is damaging the body regenerates the damage receptors and that is called neurogenesis. As human we have the keen of smell that is called microsmatic which is not critical to survival. If we loss the sense of smell or damage the olfactory system do to injury or infection it is called anosmia. the fact that the sense of smell plays a major role to our survival is something that we fall to notice in everyday life, but it is do to detection threshold which we can detect do to low contractions of a smell, if it is a strong smell it is irritating to the receptors, which can make us throw-up or make our eyes tear up. in other cases the smells that he know are known as the recognition threshold such as we use with Hennings prism to detect putrid, etheral,resinous, spicy, fragrant, and burned are located. which send a signal to the glomeruil cells that then send a signal to primary olfactory cortex located under the temporal lobe, and then to the secondary olfactory cortex located in the frontal lobe, near the eyes.
The book (Wolfe) begins the chapter on olfaction by indicating that odors are chemical compounds, however, not every chemical can be smelled. The oderant must be able to float through the air (volatile), be small, and also be repellent to water (hydrophobic). Olfaction is actually somewhat a secondary function of the nose, which is primarily intended to filter, warm, and humidify the air we breath. The nose has a structure called the olfactory epithelium, which is a mucus membrane containing cells that help detect odor. Among these cells are the olfctory sensory neurons (ONS) which contain the receptor sites for odorant molecules. Sadly, some people have smell blindness, or anosmia, and are unable detect any smells at all (a disorder or malfunction of the ONS). Interestingly, the book indicates that the absolute threshold for a human to detect odor is one drop of perfume in three rooms.
The article details how we as humans are able to sense different odors in our environment and how we are able to distinguish one smell from another. In order to experience a smell, we inhale air which then passes through three bones in the upper nose. If odor is detected, the air is sniffed further upwards into the smelling organs; two yellowish patches of tissue containing fibers that act as receptors, detecting odor molecules. Once an odor is detected by the receptors, information is sent by the olfactory nerve endings to the olfactory bulb which then sends further information to the brain for interpretation. In order for a smell to be perceived by humans it must be volatile, meaning it gives off ample vapors which contain the odor molecules needed to detect a smell. The molecules must then also be water-soluble, otherwise they cannot pass through a watery layer covering the olfactory nerves. Amoore (1952) found that humans have receptors for detecting seven different basic smells. Amoore's stereochemical theory of odor holds that each odor molecule has an atypical size and shape relative to its source. This means that the vapor coming from an apple contain very differently shaped molecules than those of a can of bleach. These molecules essentially act as 'keys' into our receptors; each key unlocks a different odor for our brain to interpret. Interestingly, this theory of olfaction was originally formulated two thousand years ago by a poet named Lucretius. Continuing, Amoore found seven basic odors that humans are able to detect; camphoraceous, musky, pepperminty, floral, ethereal, pungent, and putrid. Every smell that we interpret is the result of these or a combination of these basic odor molecules. Scientists are even able to synthesize a smell in the laboratory by mimicking the number and shape of atoms of certain smells found in nature.
The book (Goldstein)explains that the sense of smell has 2 functions; it help identify things that should be consumed because our body needs them for survival, and to detect things that should be rejected because they would be bad for our body. For humans however, having a less keen sense of smell is not crucial for their survival in comparison to other species. The abilities of our sense of smell usually go unnoticed so some important facts to know are that our olfactory receptors can be excited by the action of just one molecule of odorant and we can detect small differences of 5 to 10 percent in odor intensity. Humans also can recognize other people based on their odors and with training, identify almost 100 percent of common substances. Unfortunately, the ability to smell can be lost due to injury or infection and the name of this condition is called anosmia. The olfactory system starts on the olfactory mucosa which is a dime-sized region made up of olfactory receptor neurons (ORN) located in the nostrils. These neurons have protruding cilia where the olfactory receptors are located, and when these receptors are stimulated by odorants the process of olfaction begins. The stimulation triggers a series of reactions that cause an electrical signal in the cilium and later is transmitted to the rest of the ORNs, where it gets send to the olfactory bulb of the brain. In regards out ability to recognize smells, the book explains that odor molecules are linked to a neural code rather than molecular structure because it has been difficult to determine a relationship between the odors we perceive and their physical and chemical properties. Current research has found that some ORNs respond specifically to odorants that share a chemical feature called an odotope, so odorants are generally represented by that specific pattern of response that is activated in the olfactory bulb. In other words, each chemical causes a different pattern of activation of ORNs that can be mapped in the olfactory bulb in the frontal cortex of the brain.
This article talks about the description of odor and describes the stereochemical theory which is one of many theories that attempts to explain the olfactory process. The general idea of this theory seems to be accurate since it coincides in many aspects with current research. According to this theory, the geometric shape of the molecules and their electric change are the main determinants of odor. Furthermore, there are 3 basic properties that a material must have to be able to be smelled; it has to be volatile, should be soluble in water, and also soluble in lipids. The process of odor recognition starts as described above, but here the difference is that each ORN represent a 1 of the 7 primary odors so a reaction will occur when a primary odor fits into the corresponding receptor. The 7 primary odors are: camphoraceous which have a spherical shape, musky which have a disk shape, floral have a disk shape with an attached tail, pepperminty have a wedge shape, and ethereal have rod shape. The other 2 odors differ on their electric charge not their shape; pungent have a positive charge and putrid, a negative. Other odors are composed of several of these primaries combines in different proportions so in this case, the smell that predominates is the one that fits the better in its matching site.
the Article by Amoore,Johnston, & Rubin(1964)states that the smell is a chemical sense that is proverbial. Chemist analyze the chemical compound that create smells such as camphor (odor of camphoraseous=moth repellent), pentadecanolactone (odor of musky scent= angelica root oil), Phenylethyl methyl ethyl carbinol (odor of floral scent= roses), menthone (peppermint=mint candy), ethylene dichloride (odor of ethereal= dry cleaning fluid), Formic acid (odor of pungent=vinegar), & Bytyl mercaptian (odor of putrid=bad eggs) each chemical compound fit in as a lock in key factor that connects to the receptor sites based of the chemical compound shape, such as kite shape, wedge shape, rod shape. the anatomy of the olfactory system the inner nose contains olfactory hairs covered by mucus so no foreign pathogens will enter the body. trigeminal ending that contains supporting cells and olfactory cells as the olfactory nerve fibers that connect to olfacotry bulb, that contains within the trigeminal nerve.
1.)My text states that olfaction is extremely important in the lives of any species because it is often their primary window to the environment. One important contrast between humans and other species is that many animals are macrosmatic, which means having a keen sense of smell that is important to their survial. Humans are microsmatic, which means having a less keen sense of smell that is not crucial to their survival. The powers of the human olfactory system have often been underrated, espeically when human olfactory capabilities are compared to the olfactory powers of other animals. The book states some interesting facts that put human olfactory systems sinto perspective.
Fact #1: Although humans are less sensitive than many other animals to odors, humans olfactory receptors are exquisitely sensitive. A human's receptors can be excited by the action of just one molecule of odorant.
Fact #2: Humans are capable of detecting small differences in odor intensity. The ability to detect differences in intensity is indicated by the difference threshold, which is the smallest difference in intensity between two stimuli that can just be detected.
Fact #3: Although it is often difficult to recognize some odors, the ability to do this improves with training. Humans can tell the difference between at least 10,000 different odors.
Fact #4: Human olfaction has the potential to provide information about other people.
The text also states that the olfactory receptor neuron is where transduction (the transformation from chemicals into electric signals) occurs. The site of the transformation is the olfactory receptor. Olfactory receptors are found on cilia located at the end of the neurons. The olfactory receptor is a protein molecule consisting of srings of amino acids that cross the membrane of the receptor neuron seven times. Using new genetic techniques, researchers have recently been able to show that there are 1,000 different kinds of olfactory receptors, each of which responds to the same group of oderants.
2.)The article states that although it is easy for our nose to smell the difference between a skunk and a rose, we know little about the sense of smell. We have no tool for measuring the strength of odors, and there is no theory to explain how the brain and nose identify, detect or recognnize an odor. There have been over 30 different theories suggested by researchers but none of then have worked. The article also states that the sense of smell is a chemical sense and it is very sensitive. There are two types of nerve fibers where the endings receive and detect odorous molecules. The main type is represented by the fibers of the olfactory nerve, and at the end of these fibers there is an olfactory cell that has a cluster of hairlike filaments that act as receptors. The other type of fiber ends at the the trigeminal nerve and is sensitive to certain kinds of molecules. When stimulated by odorous molecules, the olfactory nerve endings send signals to the olfactory bulb and then to the higher brain centers where the signals interpret the character and intensity of the odor. The article talks about seven primary odors: camphoraceous, musky, floral, pepperminty, ethereal, pungent, and putrid.
The sense of smell is also known as the olfaction sense. The book talks about the odor threshold, or at what point the nose begins to pick up smells from the environment. Humans tend to have a very strong olfaction sense, it can lead us to often pick up ques from our environment. Animals often have even better olfcation senses than humans, being able to pick up more than 1000+ smells.
It is said that the olfaction sense is in a field that has not been delved into thoroughly. Not alot of research is present on how our nose picks up odors and sends them to process in the brain. The book goes on to explain this process and how it is aided by special sensory cells in the nasal cavities.
Amore goes on to elaborate on this in his experiments. Amore builds off of the previous work of Lucretius, who originally hypothesized that the nose has specially shaped receptors for chemical smells that have special shape. Also, he shares alot of knowledge with Moncrieff, who proposess that we have primary odors. Moncrieff also agrees with Lucretius' "Lock and Key" type hypothesis.
Amore states that there must be requirements for something to be an odorant. Oderants must be soluble in lipids, soluble in water, and give off molecules for the nose to pick up. Amore also posits his Stereochemical Theory of Odor. This states that by use of Xray equipment, scientists can map out the chemical structures of certain smells. Molecules with the same relative chemical structure should then smell almost alike. Passages in the nose can be measured via microelectrode to see if they are stimulated. Like Moncrieff, Amore hypothesizes there are seven main odor receptor sites. These seven main smells can be mixed together to create almost any smell.
This article shows it importance by building a strong foundation for a theory that seems to hold up well to testing and scrutiny. Amore's work is a pillar in a field that is but recently undiscovered.
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The text I have is quite detailed on the process of how we smell. beginning with the discussion of how knowing where exactly the brain processes smell is a more recent advance in the feild. because smells are often associated with emotions and memories there was a problem differentiating which areas of the brain were simply processing the smells and nothing more. Science of course cought up with this conundrum, and has brought researchers to be able to correctly identify the olfactory cortex and the orbitofrontal cortex. most every object we come in contact with is smellable... or in a more scientific sort of description, these objects are constantly emitting molecules which can be snufed up into the nose and absorbed into the mucus layer surrounding the olfactory receptors. we humans have around 10 million of these handy things, where as dogs (who are known for their keen sense of smell) have around 1 billion. the part i find interesting about this is not that a dog has so many more, but essentially there isn't that big of a difference between dog and human olfactory receptors. each receptor can only recognize one of these scent molecules at a time so the only advantage a dog has over a human in this sense is that the dog can process more at one time than a human making them indeed more sensitive to smells. this gives my receptors quite a self esteem boost. the human olfactory system is still quite amazing even if it is not as sensitive as an animals. there is the fact that humans are very sensitive to changes in intensity, and are quite good at identifying different smells. the text quotes a study done where participants were asked to identify smells and were very accurate. humans are also sensitive on a more biological level to the smells of other humans... we can look to research done on menstrual synchrony to help provide evidence for this. also, from research i participated in a few years back. the tv show "the Doctors" ran a program on the scent of attraction where they discussed research on why some people are attracted to oneanother based on their scent, and why. they theorised that we are attracted to a genetically compatible mate who will produce healthy offspring. those with a susceptibility to certain diseases would be attracted by scent to someone who may be genetically protected. this is why we find those who we are related to to smell unpleasant when they are au natural, and those who we find attractive smelling may prove to be a good choice to procreate with. men in the study wore shirts for 24 hours with no cologne or deoderant, and us women who were in relationships with them had to sniff out our mate. my two brothers also participated, and i found thier shirts out of the 25 quite easily. my husband was dissapointed because i was debating between two shirts as his... and stragely the wife of the other shirt had the same problem. i however was quite proud of my nose that day.
anyhow, back to the text. the text is older so i don't know if more work has been done, but there is research started to find the nerological coding for smells. to try and figure out what is being sent on from these molecules to the brain. the text describes briefly the sterochemical theory of odor, briefly explaining how certain molecular shapes or electrical charges correlate with certain smells.
and that brings us to the article:
the first part of the article gives a description of the awesome abilities of our olfactory system. we in milliseconds can process and identify complex compounds that would take a chemist months to decipher. yeah me! to be smelled a substance must have certian attributes, mainly to be water and lipid soluable. this article describes the theory that there are seven primary smells, and much like the three primary colors, every smell is composed of various levels of these seven primary scents. the first five (camphoraceous, musky, floral, pepperminty, and ethereal) are shape specific where as the last two (pungent and putrid) have specific electrical charges associated with them. the article describes the various tests done that support the theory and seem to provide pretty solid eveidence that our olfactory systems work in just that way, by identifying molecules of these seven primary smells through shape specific receptors. neat stuff.
In the text it states that although humans are less sensitive to odors than other animals, our olfactory receptors are exquisitely sensitive. The human sense of smell is less acute than that of many animals. But even though other animals can detect odors that humans are not aware of, the human's individual olfactory receptors are as sensitive as any animals'. Nothing can be more sensitive than one molecule per receptor, so the human's lower sensitivity to odors compared to that of other ani mals must be due to something else. That something else is the number of receptors: only about ten millions in humans compared to about one billion int he dog. Humans are surprisingly good at detecting differences in odor intensity. The abiliity to detect differences in intensity is indicated by teh difference threshold-the smallest difference in intensity between two stimuli that can just be detected. In past, olfaction has been reputed to have the largest difference threshold of all the senses, with typical values ranging from about 25 to 33 percent. That is, the concentration of an odorant must be increased by 25 to 33 percent before a person can detect an increase in odor intensity. The olfactory system is excellent at identifying odors. Early research on odor identification seemed to indicate that our ability to identify odors is poor, because when asked to identify odors people were typically successful only about half the time. However, later experiments have shown that, under the right conditions, our abiliity to identy odors is actually quite a bit better than that. Human olfaction has the potential to provide informationa bout other people. Many animals use their sense of smell to recognize other animals.
The article states that we can decipher between different smells however; we have little knowledge of how to detect how strong a smell is going to be. Our olfactory system is very complex and there is little research to represent how different people have different strengths of smell. This article also goes into great detail about the seven primary levels of scents. The seven primary levels of scents include: camphoraceous, musky, floral, pepperminty, ethereal, pungent and putrid. The camphoraceous odor is mainly spherically shaped. The musky odor is accounted for by molecules with the shape of a disk about ten angstroms in diameter. The floral odor is caused by molecules that have the shape of a disk with a flexible tail attached-a shape somewhat like a kite. The pepperminty odor is produced by molecules with a shape of a wedge, and with a electrically polarized group of atoms, capable of forming a hydrogen bond, near the point of the wedge. The ethereal odor is due to rod-shaped or other thin molecules. The pungent and putrid odors seem to be exceptions to the Lucretian scheme of a shape-matching. The molecules responsible for these odors are of different shapes and sizes; what matters in their case is the electrical charge of the molecule. The pundgent class of odors is produced by compounds whose molecules, because of a deficiency of electrons, have a positive charge and a strong affinity for electrons; they are called electrophilic. Putrid odors, on the other hand, are caused by molecules that have an excess of electrons, and are called nucleophillic, because they are strongly attracted by the nuclei of adjacent atoms.
1) My text says that the olfactory system is the way we determine what goes into our bodies through odor. Odor can elicit memories of past experiences in order for humans to survive. Being able to smell and remember things that make us sick or smells that are poison to us is a useful survival technique. The book also mentioned that humans ability to smell is not as advanced as animals and that humans take it for granted daily. Also odors are just chemical compounds and the intensity of the compound dictates how strong the smell is when smelled. Anosmia occurs when humans are unable to detect smells in anyway shape or form. The article begins by giving a scenario of how we smell smells. The process begins by breathing air through the nose and proceeding past three bones located in the nasal passageway. When odor is noticed the smell is then processed threw the nasal membrane. The olfactory nerve sends the information to the brain in order to be processed. Amoore discovered that humans can detect seven different types of smells. He concluded that each smell has its own size and shape. The size and shape determine what smell is being smelled. The seven odors humans can smell are: camphoraceous, musky, peppermintly, floral, ethereal, pungent and putrid.