Information about Olfactory Tubercle
Olfaction (also known as olfactics) refers to the sense of smell. This sense is mediated by specialized sensory cells of the nasal cavity of vertbrates, and, by analogy, sensory cells of the antennae of invertebrates. For air-breathing animals, the olfactory system detects volatile or, in the case of the accessory olfactory system, fluid-phase chemicals. For water-dwelling organisms, e.g., fishes or crustaceans, the chemicals are present in the surrounding aqueous medium. Olfaction, along with taste, is a form of chemoreception. The chemicals themselves which activate the olfactory system, generally at very low concentrations, are called odors.
Each olfactory receptor neuron expresses only one functional odor receptor. Odor receptor nerve cells function like a key-lock system: If the airborne molecules of a certain chemical can fit into the lock, the nerve cell will respond. There are, at present, a number of competing theories regarding the mechanism of odor coding and perception. According to shape theory, each receptor detects a feature of the odor molecule. Weak-shape theory, known as odotope theory, suggests that different receptors detect only small pieces of molecules, and these minimal inputs are combined to form a larger olfactory perception (similar to the way visual perception is built up of smaller, information-poor sensations, combined and refined to create a detailed overall perception)[3]. An alternative theory, the vibration theory proposed by Luca Turin[4][5], posits that odor receptors detect the frequencies of vibrations of odor molecules in the infrared range by electron tunnelling. However, the behavioral predictions of this theory have been called into question.[6] As of yet, there is no theory that explains olfactory perception completely.
Molecules of odorants passing through the superior nasal concha of the nasal passages dissolve in the mucus lining the superior portion of the cavity and are detected by olfactory receptors on the dendrites of the olfactory sensory neurons. This may occur by diffusion or by the binding of the odorant to odorant binding proteins. The mucus overlying the epithelium contains mucopolysaccharides, salts, enzymes, and antibodies (these are highly important, as the olfactory neurons provide a direct passage for infection to pass to the brain).
Averaged activity of the receptor neuron to an odor can be measured by an electroolfactogram in vertebrates or an electroantenogram in insects.
The mitral cells leave the olfactory bulb in the lateral olfactory tract, which synapses on five major regions of the cerebrum: the anterior olfactory nucleus, the olfactory tubercle, the amygdala, the piriform cortex, and the entorhinal cortex. The anterior olfactory nucleus projects, via the anterior comissure, to the contralateral olfactory bulb, inhibiting it. The piriform cortex projects to the medial dorsal nucleus of the thalamus, which then projects to the orbitofrontal cortex. The orbitofrontal cortex mediates conscious perception of the odor. The 3-layered piriform cortex projects to a number of thalamic and hypothalamic nuclei, the hippocampus and amygdala and the orbitofrontal cortex but its function is largely unknown. The entorhinal cortex projects to the amygdala and is involved in emotional and autonomic responses to odor. It also projects to the hippocampus and is involved in motivation and memory. Odor information is easily stored in long-term memory and has strong connections to emotional memory. This is possibly due to the olfactory system's close anatomical ties to the limbic system and hippocampus, areas of the brain that have long been known to be involved in emotion and place memory, respectively.
Since any one receptor is responsive to various odorants, and there is a great deal of convergence at the level of the olfactory bulb, it seems strange that human beings are able to distinguish so many different odors. It seems that there must be a highly-complex form of processing occurring; however, as it can be shown that, while many neurons in the olfactory bulb (and even the pyriform cortex and amygdala) are responsive to many different odors, half the neurons in the orbitofrontal cortex are responsive only to one odor, and the rest to only a few. It has been shown through microelectrode studies that each individual odor gives a particular specific spatial map of excitation in the olfactory bulb. It is possible that, through spatial encoding, the brain is able to distinguish specific odors. However, temporal coding must be taken into account. Over time, the spatial maps change, even for one particular odor, and the brain must be able to process these details as well.
In insects smells are sensed by sensilla located on the antenna and first processed by the antennal lobe (analogous to the olfactory bulb), and next by the mushroom bodies.
In women, the sense of olfaction is strongest around the time of ovulation, significantly stronger than during other phases of the menstrual cycle and also stronger than the sense in males.[7]
The MHC genes (known as HLA in humans) are a group of genes present in many animals and important for the immune system; in general, offspring from parents with differing MHC genes have a stronger immune system. Fish, mice and female humans are able to smell some aspect of the MHC genes of potential sex partners and prefer partners with MHC genes different from their own.[8][9]
Many air management districts in the USA have numerical standards of acceptability for the intensity of odor that is allowed to cross into a residential property. For example, the Bay Area Air Quality Management District has applied its standard in regulating numerous industries, landfills, and sewage treatment plants. Example applications this district has engaged are the San Mateo, California wastewater treatment plant; the Shoreline Amphitheatre in Mountain View, California; and the IT Corporation waste ponds, Martinez, California.
Dogs in general have a nose approximately a hundred thousand to a million times more sensitive than a human's. Scenthounds as a group can smell one to ten million times more acutely than a human, and Bloodhounds, which have the keenest sense of smell of any dogs, have noses ten to a hundred million times more sensitive than a human's. They were bred for the specific purpose of tracking humans, and can detect a scent trail a few days old. The second-most-sensitive nose is possessed by the Basset Hound, which was bred to track and hunt rabbits and other small animals.
The sense of smell is less-developed in the catarrhine primates (Catarrhini), and nonexistent in cetaceans, which compensate with a well-developed sense of taste. In some prosimians, such as the Red-bellied Lemur, scent glands occur atop the head. In many species, olfaction is highly tuned to pheromones; a male silkworm moth, for example, can sense a single molecule of bombykol.
Fish too have a well-developed sense of smell, even though they inhabit an aquatic environment. Salmon utiize their sense of smell to identify and return to their home stream waters. Catfish use their sense of smell to identify other individual catfish and to maintain a social heirarchy. Many fishes use the sense of smell to indentify mating partners or to alert to the presence of food.
Insects primarily use their antennae for olfaction. Sensory neurons in the antenna generate odor-specific electrical signals called spikes in response to odor. They process these signals from the sensory neurons in the antennal lobe followed by the mushroom bodies and lateral horn of the brain. The antennae have the sensory neurons in the sensilla and they have their axons terminating in the antennal lobes where they synapse with other neurons there in semidelineated (with membrane boundaries) called glomeruli. These antennal lobes have two kinds of neurons, projection neurons (excitatory) and local neurons (inhibitory). The projection neurons send their axon terminals to mushroom body and lateral horn (both of which are part of the protocerebrum of the insects), and local neurons have no axons. Recordings from projection neurons show in some insects strong specialization and discrimination for the odors presented (especially for the projection neurons of the macroglomeruli, a specialized complex of glomeruli responsible for the pheromones detection). Processing beyond this level is not exactly known though some preliminary results are available.
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Mucus is a slippery secretion of the lining of the mucous membranes in the body.
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Dendrites (from Greek dendron, “tree”) are the branched projections of a neuron that act to conduct the electrical stimulation received from other neural cells to the cell body, or
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History
As described by the Roman philopsher Lucretius (1st Century BCE), different odors are attributed to different shapes and sizes of odor molecules that stimulate the olfactory organ. The modern counterpart to that theory was the discovery of odorant receptor molecules by Linda B. Buck and Richard Axel (who were awarded the Nobel Prize in 2004). Each odor receptor molecule recognizes only a particular molecular feature or class of odor molecules. Mammals have about a thousand genes expressing for odor reception.[1] Of these genes, only a portion are functional odor receptors. Humans have far fewer active odor receptor genes than other mammals and primates[2]Each olfactory receptor neuron expresses only one functional odor receptor. Odor receptor nerve cells function like a key-lock system: If the airborne molecules of a certain chemical can fit into the lock, the nerve cell will respond. There are, at present, a number of competing theories regarding the mechanism of odor coding and perception. According to shape theory, each receptor detects a feature of the odor molecule. Weak-shape theory, known as odotope theory, suggests that different receptors detect only small pieces of molecules, and these minimal inputs are combined to form a larger olfactory perception (similar to the way visual perception is built up of smaller, information-poor sensations, combined and refined to create a detailed overall perception)[3]. An alternative theory, the vibration theory proposed by Luca Turin[4][5], posits that odor receptors detect the frequencies of vibrations of odor molecules in the infrared range by electron tunnelling. However, the behavioral predictions of this theory have been called into question.[6] As of yet, there is no theory that explains olfactory perception completely.
Olfactory System
Olfactory epithelium
In vertebrates smells are sensed by olfactory sensory neurons in the olfactory epithelium. The proportion of olfactory epithelium compared to respiratory epithelium (not innervated) gives an indication of the animal's olfactory sensitivity. Humans have about sixteen cm2 of olfactory epithelium, whereas some dogs have 150 cm2. A dog's olfactory epithelium is also considerably more densely innervated, with a hundred times more receptors per square centimetre.Molecules of odorants passing through the superior nasal concha of the nasal passages dissolve in the mucus lining the superior portion of the cavity and are detected by olfactory receptors on the dendrites of the olfactory sensory neurons. This may occur by diffusion or by the binding of the odorant to odorant binding proteins. The mucus overlying the epithelium contains mucopolysaccharides, salts, enzymes, and antibodies (these are highly important, as the olfactory neurons provide a direct passage for infection to pass to the brain).
Receptor neuron
The process of how the binding of the ligand (odor molecule or odorant) to the receptor leads to an action potential in the receptor neuron is via a second messenger pathway depending on the organism. In mammals the odorants stimulate adenylate cyclase to synthesize cAMP via a G protein called Golf. cAMP, which is the second messenger here, opens a cyclic nucleotide-gated ion channel (CNG) producing an influx of cations (largely Ca2+ with some Na+) into the cell, slightly depolarising it. The Ca2+ in turn opens a Ca2+-activated chloride channel, leading to efflux of Cl-, further depolarising the cell and triggering an action potential. Ca2+ is then extruded through a sodium-calcium exchanger. A calcium-calmodulin complex also acts to inhibit the binding of cAMP to the cAMP-dependent channel, thus contributing to olfactory adaptation.''' This mechanism of transduction is somewhat unique, in that cAMP works by directly binding to the ion channel rather than through activation of protein kinase A. It is similar to the transduction mechanism for photoreceptors, in which the second messenger cGMP works by directly binding to ion channels, suggesting that maybe one of these receptors was evolutionarily adapted into the other. There are also considerable similarities in the immediate processing of stimuli by lateral inhibition.Averaged activity of the receptor neuron to an odor can be measured by an electroolfactogram in vertebrates or an electroantenogram in insects.
Olfactory Bulb Projections
Olfactory sensory neurons project axons to the brain within the olfactory nerve, (cranial nerve I). These axons pass to the olfactory bulb through the cribriform plate, which in-turn projects olfactory information to the olfactory cortex and other areas. The axons from the olfactory receptors converge in the olfactory bulb within small (~50 micrometers in diameter) structures called glomeruli. Mitral cells in the olfactory bulb form synapses with the axons within glomeruli and send the information about the odor to multiple other parts of the olfactory system in the brain, where multiple signals may be processed to form a synthesized olfactory perception. There is a large degree of convergence here, with twenty-five thousand axons synapsing on one hundred or so mitral cells, and with each of these mitral cells projecting to multiple glomeruli. Mitral cells also project to periglomerular cells and granular cells that inhibit the mitral cells surrounding it (lateral inhibition). Granular cells also mediate inhibition and excitation of mitral cells through pathways from centrifugal fibres and the anterior olfactory nuclei.The mitral cells leave the olfactory bulb in the lateral olfactory tract, which synapses on five major regions of the cerebrum: the anterior olfactory nucleus, the olfactory tubercle, the amygdala, the piriform cortex, and the entorhinal cortex. The anterior olfactory nucleus projects, via the anterior comissure, to the contralateral olfactory bulb, inhibiting it. The piriform cortex projects to the medial dorsal nucleus of the thalamus, which then projects to the orbitofrontal cortex. The orbitofrontal cortex mediates conscious perception of the odor. The 3-layered piriform cortex projects to a number of thalamic and hypothalamic nuclei, the hippocampus and amygdala and the orbitofrontal cortex but its function is largely unknown. The entorhinal cortex projects to the amygdala and is involved in emotional and autonomic responses to odor. It also projects to the hippocampus and is involved in motivation and memory. Odor information is easily stored in long-term memory and has strong connections to emotional memory. This is possibly due to the olfactory system's close anatomical ties to the limbic system and hippocampus, areas of the brain that have long been known to be involved in emotion and place memory, respectively.
Since any one receptor is responsive to various odorants, and there is a great deal of convergence at the level of the olfactory bulb, it seems strange that human beings are able to distinguish so many different odors. It seems that there must be a highly-complex form of processing occurring; however, as it can be shown that, while many neurons in the olfactory bulb (and even the pyriform cortex and amygdala) are responsive to many different odors, half the neurons in the orbitofrontal cortex are responsive only to one odor, and the rest to only a few. It has been shown through microelectrode studies that each individual odor gives a particular specific spatial map of excitation in the olfactory bulb. It is possible that, through spatial encoding, the brain is able to distinguish specific odors. However, temporal coding must be taken into account. Over time, the spatial maps change, even for one particular odor, and the brain must be able to process these details as well.
In insects smells are sensed by sensilla located on the antenna and first processed by the antennal lobe (analogous to the olfactory bulb), and next by the mushroom bodies.
Pheromonal olfaction
Many animals, including most mammals and reptiles, have two distinct and segregated olfactory systems: a main olfactory system, which detects volatile stimuli, and an accessory olfactory system, which detects fluid-phase stimuli. Behavioral evidence suggests that these fluid-phase stimuli often function as pheromones, although pheromones can also be detected by the main olfactory system. In the accessory olfactory system, stimuli are detected by the vomeronasal organ, located in the vomer, between the nose and the mouth. Snakes use it to smell prey, sticking their tongue out and touching it to the organ. Some mammals make a face called flehmen to direct air to this organ.In women, the sense of olfaction is strongest around the time of ovulation, significantly stronger than during other phases of the menstrual cycle and also stronger than the sense in males.[7]
The MHC genes (known as HLA in humans) are a group of genes present in many animals and important for the immune system; in general, offspring from parents with differing MHC genes have a stronger immune system. Fish, mice and female humans are able to smell some aspect of the MHC genes of potential sex partners and prefer partners with MHC genes different from their own.[8][9]
Olfaction and taste
Olfaction, taste and trigeminal receptors together contribute to flavor. The human tongue can distinguish only among five distinct qualities of taste, while the nose can distinguish among hundreds of substances, even in minute quantities. Olfaction amplifies the sense of taste, as can be proven by a simple "kitchen" experiment. If peeled pieces of apple are placed in one bowl, and peeled pieces of potato in another, and then the nostrils are held completely closed while a piece from one bowl is sampled, the taste of apple and potato are indistinguishable.Disorders of olfaction
The following are disorders of olfaction:[10]- Anosmia - lack of ability to smell
- Hyposmia - decreased ability to smell
- Phantosmia - "hallucinated smell", often unpleasant in nature
- Dysosmia - things smell differently than they should
- Hyperosmia - an abnormally acute sense of smell
Quantifying Olfaction in Industry
Scientists have devised methods for quantifying the intensity of odors, particularly for the purpose of analyzing unpleasant or objectionable odors released by an industrial source into a community. Since the 1800s, industrial countries have encountered incidents where proximity of an industrial source or landfill produced adverse reactions to nearby residents regarding airborne odor. The basic theory of odor analysis is to measure what extent of dilution with "pure" air is required before the sample in question is rendered indistinguishable from the "pure" or reference standard. Since each person perceives odor differently, an "odor panel" composed of several different people is assembled, each sniffing the same sample of diluted specimen air.Many air management districts in the USA have numerical standards of acceptability for the intensity of odor that is allowed to cross into a residential property. For example, the Bay Area Air Quality Management District has applied its standard in regulating numerous industries, landfills, and sewage treatment plants. Example applications this district has engaged are the San Mateo, California wastewater treatment plant; the Shoreline Amphitheatre in Mountain View, California; and the IT Corporation waste ponds, Martinez, California.
Olfaction in non-human animals
The importance and sensitivity of smell varies among different organisms; most mammals have a good sense of smell, whereas most birds do not, except the tubenoses (e.g., petrels and albatrosses), and the kiwis. Among mammals, it is well-developed in the carnivores and ungulates, who must always be aware of each other, and in those, such as the moles, that smell for their food.Dogs in general have a nose approximately a hundred thousand to a million times more sensitive than a human's. Scenthounds as a group can smell one to ten million times more acutely than a human, and Bloodhounds, which have the keenest sense of smell of any dogs, have noses ten to a hundred million times more sensitive than a human's. They were bred for the specific purpose of tracking humans, and can detect a scent trail a few days old. The second-most-sensitive nose is possessed by the Basset Hound, which was bred to track and hunt rabbits and other small animals.
The sense of smell is less-developed in the catarrhine primates (Catarrhini), and nonexistent in cetaceans, which compensate with a well-developed sense of taste. In some prosimians, such as the Red-bellied Lemur, scent glands occur atop the head. In many species, olfaction is highly tuned to pheromones; a male silkworm moth, for example, can sense a single molecule of bombykol.
Fish too have a well-developed sense of smell, even though they inhabit an aquatic environment. Salmon utiize their sense of smell to identify and return to their home stream waters. Catfish use their sense of smell to identify other individual catfish and to maintain a social heirarchy. Many fishes use the sense of smell to indentify mating partners or to alert to the presence of food.
Insects primarily use their antennae for olfaction. Sensory neurons in the antenna generate odor-specific electrical signals called spikes in response to odor. They process these signals from the sensory neurons in the antennal lobe followed by the mushroom bodies and lateral horn of the brain. The antennae have the sensory neurons in the sensilla and they have their axons terminating in the antennal lobes where they synapse with other neurons there in semidelineated (with membrane boundaries) called glomeruli. These antennal lobes have two kinds of neurons, projection neurons (excitatory) and local neurons (inhibitory). The projection neurons send their axon terminals to mushroom body and lateral horn (both of which are part of the protocerebrum of the insects), and local neurons have no axons. Recordings from projection neurons show in some insects strong specialization and discrimination for the odors presented (especially for the projection neurons of the macroglomeruli, a specialized complex of glomeruli responsible for the pheromones detection). Processing beyond this level is not exactly known though some preliminary results are available.
References
1. ^ Buck, Linda and Richard Axel. (1991). A Novel Multigene Family May Encode Odorant Receptors: A Molecular Basis for Odor Recognition. Cell 65:175-183.
2. ^ Gilad Y, Man O, Pääbo S, Lancet D (2003) Human specific loss of olfactory receptor genes. Proc Natl Acad Sci U S A 100:3324–3327.
3. ^ need citation!
4. ^ Turin, Luca. (1996). A spectroscopic mechanism for primary olfactory reception. Chemical Senses, 21, 773-791.
5. ^ Turin, Luca. (2002). A method for the calculation of odor character from molecular structure. Journal of Theoretical Biology, 216, 367-385.
6. ^ Keller, A and Vosshall, LB. (2004). A psychophysical test of the vibration theory of olfaction. Nature Neuroscience 7:337-338. See also the editorial on p. 315.
7. ^ Navarrete-Palacios E, Hudson R, Reyes-Guerrero G, Guevara-Guzman R. "Lower olfactory threshold during the ovulatory phase of the menstrual cycle." Biol Psychol. 2003 Jul;63(3):269-79. PMID 12853171
8. ^ Boehm T, Zufall F. "MHC peptides and the sensory evaluation of genotype." Trends Neurosci. 2006 Feb;29(2):100-7. PMID 16337283
9. ^ Santos PS, Schinemann JA, Gabardo J, Bicalho Mda G. "New evidence that the MHC influences odor perception in humans: a study with 58 Southern Brazilian students." Horm Behav. 2005 Apr;47(4):384-8.
10. ^ Hirsch, Alan R. (2003) Life's a Smelling Success
2. ^ Gilad Y, Man O, Pääbo S, Lancet D (2003) Human specific loss of olfactory receptor genes. Proc Natl Acad Sci U S A 100:3324–3327.
3. ^ need citation!
4. ^ Turin, Luca. (1996). A spectroscopic mechanism for primary olfactory reception. Chemical Senses, 21, 773-791.
5. ^ Turin, Luca. (2002). A method for the calculation of odor character from molecular structure. Journal of Theoretical Biology, 216, 367-385.
6. ^ Keller, A and Vosshall, LB. (2004). A psychophysical test of the vibration theory of olfaction. Nature Neuroscience 7:337-338. See also the editorial on p. 315.
7. ^ Navarrete-Palacios E, Hudson R, Reyes-Guerrero G, Guevara-Guzman R. "Lower olfactory threshold during the ovulatory phase of the menstrual cycle." Biol Psychol. 2003 Jul;63(3):269-79. PMID 12853171
8. ^ Boehm T, Zufall F. "MHC peptides and the sensory evaluation of genotype." Trends Neurosci. 2006 Feb;29(2):100-7. PMID 16337283
9. ^ Santos PS, Schinemann JA, Gabardo J, Bicalho Mda G. "New evidence that the MHC influences odor perception in humans: a study with 58 Southern Brazilian students." Horm Behav. 2005 Apr;47(4):384-8.
10. ^ Hirsch, Alan R. (2003) Life's a Smelling Success
See also
External links
- Smells and Odours - How Smell Works at thenakedscientists.com
- Olfaction at cf.ac.uk
- The importance of smell, and pheromones, to Humans and other Animals at thenakedscientists.com
- Structure-odor relations: a modern perspective at flexitral.com (PDF)
- Olfactory network dynamics and the coding of multidimensional signals at caltech.edu (PDF)
- Olfaction at leffingwell.com
- Chirality & Odour Perception at leffingwell.com
- ScienceDaily Artille 08/03/2006, Quick -- What's That Smell? Time Needed To Identify Odors Reveals Much About Olfaction at sciencedaily.com
- Scents and Emotions Linked by Learning, Brown Study Shows at brown.edu.com
- Sense of Smell Institute at senseofsmell.org. Research arm of international fragrance industry's The Fragrance Foundation
Senses are the physiological methods of perception. The senses and their operation, classification, and theory are overlapping topics studied by a variety of fields, most notably neuroscience, cognitive psychology (or cognitive science), and philosophy of perception.
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The Accessory olfactory system (AOS) is one of the two olfactory systems commonly found in vertebrates. Like the main olfactory system, the accessory olfactory system is a chemosensory system, which tranduces chemicals into neural activity.
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Taste (or more formally, gustation) is a form of direct chemoreception and is one of the traditional five senses. It refers to the ability to detect the flavor of substances such as food and poisons.
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A chemosensor, also known as chemoreceptor, is a cell or group of cells that transduce a chemical signal into an action potential. Or, more generally, a chemosensor detects certain chemical stimuli in the environment.
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odor or odour (see spelling differences) is a volatilized chemical compound, generally at a very low concentration, which humans and other animals perceive by the sense of olfaction. Odors are also called smells, which can refer to both pleasant and unpleasant odors.
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Linda B. Buck, Ph.D., (born January 29, 1947) is an American biologist best known for her work on the olfactory system. She and Richard Axel won the 2004 Nobel Prize in Physiology or Medicine for their work on olfactory receptors.
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Richard Axel, M.D. (born July 2, 1946, New York City) is an American scientist whose work on the olfactory system won him and Linda B. Buck, a former post-doctoral scientist in his research group, the Nobel Prize in Physiology or Medicine in 2004.
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This page is currently protected from editing until disputes have been resolved.
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Mammalia
Linnaeus, 1758
Subclasses & Infraclasses
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Linnaeus, 1758
Subclasses & Infraclasses
- Subclass †Allotheria*
- Subclass Prototheria
- Subclass Theria
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For a non-technical introduction to the topic, see .
A gene is a locatable region of genomic sequence, corresponding to a unit of inheritance, which is associated with regulatory regions, transcribed regions and/or other functional sequence regions...... Click the link for more information.
Olfactory receptors are class A G protein-coupled receptor which play a role in signal transduction to olfactory receptor neurons.
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Expression
In vertebrates, the olfactory receptors are located in the cilia of the olfactory sensory neurons...... Click the link for more information.
For a non-technical introduction to the topic, see .
A gene is a locatable region of genomic sequence, corresponding to a unit of inheritance, which is associated with regulatory regions, transcribed regions and/or other functional sequence regions...... Click the link for more information.
Location olfactory epithelium in the nose
Function Detect traces of chemicals in inhaled air (sense of smell)
Neurotransmitter Glutamate
Morphology Bipolar sensory receptor
Presynaptic connections None
Postsynaptic connections
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Function Detect traces of chemicals in inhaled air (sense of smell)
Neurotransmitter Glutamate
Morphology Bipolar sensory receptor
Presynaptic connections None
Postsynaptic connections
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The Shape theory of smell states that the sensation of smell is due to a 'lock and key' mechanism by which a scent molecule fits into olfactory receptors in the nasal lamina of the nose.
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Support
Dr. John E. Amoore came up with the shape theory in 1952 at Oxford University...... Click the link for more information.
molecule is defined as a sufficiently stable electrically neutral group of at least two atoms in a definite arrangement held together by strong chemical bonds.[1][2] In organic chemistry and biochemistry, the term molecule
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Odotope Theory, also known as Weak-Shape Theory, is a leading neurophysiological theory of how the sense of smell functions. The model is analogous to a molecular Braille: it is propsed that any number of the 347 different protein-based smell receptors in the nose binds to only
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The Vibration theory (or more precisely, hypothesis) of smell is that the quality of a particular odour arises from olfactory receptors' responding to frequencies of vibrations of odour molecules in the infrared range.
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Luca Turin (1953 - ) is a biophysicist with a long-standing interest in the sense of smell, the art of perfume, and the fragrance industry.
Since 1996 Turin has been the leading proponent of the vibration theory of olfaction, which proposes that the vibrational spectroscopic
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Since 1996 Turin has been the leading proponent of the vibration theory of olfaction, which proposes that the vibrational spectroscopic
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In quantum mechanics, quantum tunnelling is a micro and nanoscopic phenomenon in which a particle violates principles of classical mechanics by penetrating or passing through a potential barrier or impedance higher than the kinetic energy of the particle.
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Vertebrata
Cuvier, 1812
Classes and Clades
See below
Vertebrates are members of the subphylum Vertebrata (within the phylum Chordata), specifically, those chordates with backbones or spinal columns.
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Cuvier, 1812
Classes and Clades
See below
Vertebrates are members of the subphylum Vertebrata (within the phylum Chordata), specifically, those chordates with backbones or spinal columns.
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Location olfactory epithelium in the nose
Function Detect traces of chemicals in inhaled air (sense of smell)
Neurotransmitter Glutamate
Morphology Bipolar sensory receptor
Presynaptic connections None
Postsynaptic connections
..... Click the link for more information.
Function Detect traces of chemicals in inhaled air (sense of smell)
Neurotransmitter Glutamate
Morphology Bipolar sensory receptor
Presynaptic connections None
Postsynaptic connections
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The olfactory epithelium is a specialized epithelial tissue inside the nasal cavity that is involved in smell. In humans, it measures about 1 inch wide by 2 inches long (about 2 cm by 5 cm) and lies on the roof of the nasal cavity about 3 inches (about 7 cm) above and behind the
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epithelium is a tissue composed of a layer of cells. Epithelium lines both the outside (skin) and the inside cavities and lumen of bodies. The outermost layer of our skin is composed of dead stratified squamous, keratinized epithelial cells.
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superior nasal concha.
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See also
- Nasal concha
Additional images
Ethmoid bone from the right side.
Horizontal section of nasal and orbital cavities.
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highly specialized aspect of its associated subject.
Please help [ improve this article] by adding more general information.
Please help [ improve this article] by adding more general information.
Mucus is a slippery secretion of the lining of the mucous membranes in the body.
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Olfactory receptors are class A G protein-coupled receptor which play a role in signal transduction to olfactory receptor neurons.
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Expression
In vertebrates, the olfactory receptors are located in the cilia of the olfactory sensory neurons...... Click the link for more information.
For the dendritic crystal structure, see .
Dendrites (from Greek dendron, “tree”) are the branched projections of a neuron that act to conduct the electrical stimulation received from other neural cells to the cell body, or
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Odorant binding proteins are abundant small soluble proteins secreted in the nasal mucus of many animal species. These proteins were initially identified on the basis of their ability to bind with moderate affinity radioactively labeled odorants (Pelosi et al., 1982).
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Glycosaminoglycans (GAGs) or mucopolysaccharides are long unbranched polysaccharides consisting of a repeating disaccharide unit.
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Production
Protein cores made in the rough endoplasmic reticulum are posttranslationally modified by glycosyltransferases in the Golgi..... Click the link for more information.
Enzymes are proteins that catalyze (i.e. accelerate) chemical reactions.[1] In enzymatic reactions, the molecules at the beginning of the process are called substrates, and the enzyme converts them into different molecules, the products.
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Herod_Archelaus
