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Encyclopedia > Olfaction

Olfaction (also known as olfactics) refers to the sense of smell. This sense is mediated by specialized sensory cells of the nasal cavity of vertebrates, 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. Senses are the physiological methods of perception. ... The Accessory olfactory system (AOS) is one of the two olfactory systems commonly found in vertebrates. ... Taste is one of the traditional five senses and refers to the ability to detect the flavor of foodstuffs and other substances (e. ... A Chemosensor, also known as chemoreceptor, is a cell or group of cells that transduce a chemical signal into an action potential. ... “Aroma” redirects here. ...

Neuroscience Portal

Contents

Image File history File links No higher resolution available. ...

History

As described by the Roman philosopher 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] samantha is one freakin hottie and this site is stuuuuuuuupid =] Linda B. Buck, Ph. ... 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. ... The Nobel Prizes (Swedish: ), as designated in Alfred Nobels will in 1895, are awarded for physics, chemistry, physiology or medicine, literature, and peace. ... Orders Subclass Monotremata Monotremata Subclass Marsupialia Didelphimorphia Paucituberculata Microbiotheria Dasyuromorphia Peramelemorphia Notoryctemorphia Diprotodontia Subclass Placentalia Xenarthra Dermoptera Desmostylia Scandentia Primates Rodentia Lagomorpha Insectivora Chiroptera Pholidota Carnivora Perissodactyla Artiodactyla Cetacea Afrosoricida Macroscelidea Tubulidentata Hyracoidea Proboscidea Sirenia The mammals are the class of vertebrate animals primarily characterized by the presence of mammary... For other uses, see Gene (disambiguation). ... Olfactory receptors are a type of G protein-coupled receptor in olfactory receptor neurons. ... For other uses, see Gene (disambiguation). ...


Each olfactory receptor neuron expresses only one functional odor receptor.[citation needed] 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. Bold text == Headline text == minni hi. ... 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 a receptor site in the nose. ... 3D (left and center) and 2D (right) representations of the terpenoid molecule atisane. ... Odotope Theory, also known as Weak-Shape Theory, is a leading neurophysiological theory of how the sense of smell functions. ... According to this theory the sensation of smell arises from the noses sensing of the rate of electron tunneling into the scent molecule. ... Luca Turin (1953 - ) is a biophysicist with a long-standing interest in scent, fragrance and the perfume industry. ... Quantum tunneling is the quantum-mechanical effect of transitioning through a classically-forbidden energy state. ...


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. This article does not cite any references or sources. ... An olfactory receptor neuron, also called an olfactory sensory neuron, is the primary transduction cell for olfaction in the olfactory system. ... The olfactory epithelium is a specialized epithelial tissue inside the nasal cavity that is involved in smell. ... This article is about the epithelium as it relates to animal anatomy. ...


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). The back part of the medial surface of the labyrinth of ethmoid is subdivided by a narrow oblique fissure, the superior meatus of the nose, bounded above by a thin, curved plate, the superior nasal concha. ... Mucus is a slippery secretion of the lining of the mucous membranes in the body. ... Olfactory receptors are a type of G protein-coupled receptor in olfactory receptor neurons. ... In biology, a dendrite is a slender, typically branched projection of a nerve cell, or neuron, which conducts the electrical stimulation received from other cells to the body or soma of the cell from which it projects. ... Odorant binding proteins are abundant small soluble proteins secreted in the nasal mucus of many animal species and in the sensillar lymph of chemosensory sensilla of insects. ... Glycosaminoglycans (GAGs) are long unbranched polysaccharides, made up of repeating disaccharides that may be sulphated (e. ... Neuraminidase ribbon diagram An enzyme (in Greek en = in and zyme = blend) is a protein, or protein complex, that catalyzes a chemical reaction and also controls the 3D orientation of the catalyzed substrates. ... Wikipedia does not yet have an article with this exact name. ... The human brain In animals, the brain (enkephalos) (Greek for in the skull), is the control center of the central nervous system, responsible for behavior. ...


In insects smells are sensed by olfactory sensory neurons in the chemosensory sensilla, which are present in insect antenna, palps and tarsa, but also on other parts of the insect body. Odorants penetrate into the cuticle pores of chemosensory sensilla and get in contact with insect Odorant binding proteins (OBPs) or Chemosensory proteins (CSPs), before activating the sensory neurons. Orders Subclass Apterygota Symphypleona - globular springtails Subclass Archaeognatha (jumping bristletails) Subclass Dicondylia Monura - extinct Thysanura (common bristletails) Subclass Pterygota Diaphanopteroidea - extinct Palaeodictyoptera - extinct Megasecoptera - extinct Archodonata - extinct Ephemeroptera (mayflies) Odonata (dragonflies and damselflies) Infraclass Neoptera Blattodea (cockroaches) Mantodea (mantids) Isoptera (termites) Zoraptera Grylloblattodea Dermaptera (earwigs) Plecoptera (stoneflies) Orthoptera (grasshoppers, crickets... An olfactory receptor neuron, also called an olfactory sensory neuron, is the primary transduction cell for olfaction in the olfactory system. ... Sensilla (sg. ... Odorant binding proteins are abundant small soluble proteins secreted in the nasal mucus of many animal species and in the sensillar lymph of chemosensory sensilla of insects. ... Chemosensory proteins are a class of small (10-15 kDa), soluble proteins characterised for the first time by Angeli et al. ...


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. In chemistry, a ligand is an atom, ion, or molecule (see also: functional group) that generally donates one or more of its electrons through a coordinate covalent bond to, or shares its electrons through a covalent bond with, one or more central atoms or ions (these ligands act as a... A. A schematic view of an idealized action potential illustrates its various phases as the action potential passes a point on a cell membrane. ... In biology, second messengers are low-weight diffusible molecules that are used in signal transduction to relay signals within a cell. ... Epinephrine binds its receptor, that associates with an heterotrimeric G protein. ... Structure of cAMP cAMP represented in three ways, the left with sticks-representation, the middle with structure formula, and the right with space filled representation. ... G-proteins, short for guanine nucleotide binding proteins, are a family of proteins involved in second messenger cascades. ... A Cyclic nucleotide-gated ion channel is any ion channel that opens in the presence of cyclic nucleotides. ... A cation is an ion with positive charge. ... For other uses, see Calcium (disambiguation). ... For sodium in the diet, see Edible salt. ... Ion channels are present in the membranes that surround all biological cells. ... General Name, symbol, number chlorine, Cl, 17 Chemical series halogens Group, period, block 17, 3, p Appearance yellowish green Standard atomic weight 35. ... A. A schematic view of an idealized action potential illustrates its various phases as the action potential passes a point on a cell membrane. ... The sodium-calcium exchanger (often denoted Na+/Ca2+ exchanger or exchange protein) is an antiporter ion pump membrane protein which removes calcium from cells. ... oommen sir is a fool. ... Ion channels are pore-forming proteins that help to establish and control the small voltage gradient that exists across the plasma membrane of all living cells (see cell potential) by allowing the flow of ions down their electrochemical gradient. ... In cell biology, cAMP-dependent protein kinase (cAPK), also known as protein kinase A (PKA)(EC 2. ... A photoreceptor, or photoreceptor cell, is a specialized type of neuron found in the eyes retina that is capable of phototransduction. ... Cyclic guanosine monophosphate (cGMP) is a second messenger derived from GTP. Cyclic guanosine monophosphate (cGMP) is a cyclic nucleotide derived from guanosine triphosphate (GTP). ... simply; your nose receives messages from the environment sending them to the olfactory centre which is present in the cerebrum the largest part of brain: then you either smell a good smell or a bad smell stink with parts of seconds. ...


Averaged activity of the receptor neuron to an odor can be measured by an electroolfactogram in vertebrates or an electroantenogram in insects. Electroantennogram or EAG is a technique by which we measure the average output of the antenna to the brain for a given odor. ...


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. An axon or nerve fiber, is a long, slender projection of a nerve cell, or neuron, that conducts electrical impulses away from the neurons cell body or soma. ... The olfactory nerve is the first of twelve cranial nerves. ... Cranial nerves are nerves which start directly from the brainstem instead of the spinal cord. ... The olfactory bulb is a structure of the vertebrate forebrain involved in olfaction, the perception of odors. ... The cribriform plate of the ethmoid bone (horizontal lamina) [Fig. ... The olfactory system is the sensory system used for olfaction. ... Olfactory receptors are a type of G protein-coupled receptor in olfactory receptor neurons. ... The olfactory bulb is a structure of the vertebrate forebrain involved in olfaction, the perception of odors. ... Glomerulus refers to two unrelated structures in the body, both named for their globular form. ... Mitral cells are neurons that make up a part of the olfactory system. ... “Aroma” redirects here. ... Drawing of Purkinje cells (A) and granule cells (B) from pigeon cerebellum by Santiago Ramón y Cajal, 1899. ... simply; your nose receives messages from the environment sending them to the olfactory centre which is present in the cerebrum the largest part of brain: then you either smell a good smell or a bad smell stink with parts of seconds. ...


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. The anterior olfactory nucleus is a cranial nucleus for the olfactory nerve. ... Young boy smelling a flower Olfaction, the sense of smell, is the detection of chemicals dissolved in air. ... Look up Amygdala in Wiktionary, the free dictionary. ... In anatomy of animals, the piriform cortex, or pyriform cortex is a region in the brain. ... The entorhinal cortex (EC) is an important memory center in the brain. ... The Anterior Commissure (precommissure) is a bundle of white fibers, connecting the two cerebral hemispheres across the middle line, and placed in front of the columns of the fornix. ... The medial dorsal nucleus is a a large nucleus in the thalamus. ... Look up Amygdala in Wiktionary, the free dictionary. ... Long-term memory (LTM) is memory, stored as meaning, that can last as little as 30 seconds or as long as decades. ... Emotional memory is an element of the Stanislavski System, an approach to acting. ... The limbic system (Latin limbus: border or edge) includes the structures in the human brain involved in emotion, motivation, and emotional association with memory. ... The hippocampus is structurally located inside the medial temporal lobe of the brain. ...


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. Orders Subclass Apterygota Archaeognatha (bristletails) Thysanura (silverfish) Subclass Pterygota Infraclass Paleoptera (Probably paraphyletic) Ephemeroptera (mayflies) Odonata (dragonflies and damselflies) Infraclass Neoptera Superorder Exopterygota Grylloblattodea (ice-crawlers) Mantophasmatodea (gladiators) Plecoptera (stoneflies) Embioptera (webspinners) Zoraptera (angel insects) Dermaptera (earwigs) Orthoptera (grasshoppers, etc) Phasmatodea (stick insects) Blattodea (cockroaches) Isoptera (termites) Mantodea (mantids) Psocoptera... Antennal Lobe is the deutocerebral neuropil of the insect which receive the input from the sensory neurons on the antenna. ... The olfactory bulb is a structure of the vertebrate forebrain involved in olfaction, the perception of odors. ...


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. The Accessory olfactory system (AOS) is one of the two olfactory systems commonly found in vertebrates. ... Fanning honeybee exposes Nasonov gland (white-at tip of abdomen) releasing pheromone to entice swarm into an empty hive A pheromone is a chemical that triggers an innate behavioural response in another member of the same species. ... The Accessory olfactory system (AOS) is one of the two olfactory systems commonly found in vertebrates. ... The vomeronasal organ (VNO) or Jacobsons organ is an auxiliary olfactory sense organ in some tetrapods. ... The Flehmen response is a particular type of curling of the lips in ungulates, felids, and many other mammals, which facilitates the transfer of chemicals into the vomeronasal 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] Ovulation is the process in the menstrual cycle by which a mature ovarian follicle ruptures and discharges an ovum (also known as an oocyte, female gamete, or casually, an egg) that participates in reproduction. ... Menstrual cycle The menstrual cycle is a recurring cycle of physiologic changes that occurs in the females of several mammals, including human beings and other apes. ...


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] Protein images comparing the MHC I (1hsa) and MHC II (1dlh) molecules. ... HLA region of Chromosome 6 The human leukocyte antigen system (HLA) is the name of the human major histocompatibility complex (MHC). ... A scanning electron microscope image of a single neutrophil (yellow), engulfing anthrax bacteria (orange). ...


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.[citation needed] Taste is one of the traditional five senses and refers to the ability to detect the flavor of foodstuffs and other substances (e. ... The trigeminal nerve is the fifth (V) cranial nerve, and carries sensory information from most of the face, as well as motor supply to the muscles of mastication (the muscles enabling chewing), tensor tympani (in the middle ear), and other muscles in the floor of the mouth, such as the... This article is about flavor as a sensory impression. ... This article includes a list of works cited or a list of external links, but its sources remain unclear because it lacks in-text citations. ... Taste is one of the traditional five senses and refers to the ability to detect the flavor of foodstuffs and other substances (e. ...


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

Anosmia is the lack of olfaction, or a loss of the ability to smell. ... Hyposmia is a reduced ability to smell and to detect odors. ... Phantosmia is the phenomenon of smelling odors that arent really present. ... Hyperosmia is an abnormally heightened 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.-1... San Mateo is a city in San Mateo County, California, in the San Francisco Bay Area. ... Shoreline Amphitheatre as seen from ground level Aerial photograph of Shoreline Amphitheatre, with the parking lots and the neighbouring golf course Shoreline Amphitheatre is an outdoor amphitheater in Mountain View, California, USA, in the San Francisco Bay Area. ... Mountain View is a city in Santa Clara County, in the U.S. state of California. ... IT Corporation is an United States industrial company whose principal business is the disposal of industrial hazardous waste. ... John Muirs home. ...


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. Subclasses & Infraclasses Subclass †Allotheria* Subclass Prototheria Subclass Theria Infraclass †Trituberculata Infraclass Metatheria Infraclass Eutheria Mammals (class Mammalia) are warm-blooded, vertebrate animals characterized by the presence of sweat glands, including those that produce milk, and by the presence of: hair, three middle ear bones used in hearing, and a neocortex... For other uses, see Bird (disambiguation). ... Procellariiformes (from the Latin procella, a storm) is an order of birds formerly called Tubinares and still called tubenoses in English. ... The petrels are seabirds in the bird order Procellariiformes. ... This article is about the bird family. ... Species See text. ... Carnivorism redirects here. ... Orders & Clades Order Perissodactyla Eparctocyona Order Arctostylonia (extinct) Order Mesonychia (extinct) Cetartiodactyla Order Cetacea Order Artiodactyla Bulbulodentata (extinct) Family Hyopsodontidae Meridiungulata (extinct) Order Litopterna Notoungulata (extinct) Order Toxodontia Order Typotheria Ungulates (meaning roughly being hoofed or hoofed animal) are several groups of mammals most of which use the tips of... For other uses, see Mole. ...


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. Like most scent hounds, the Basset Hound has long ears, large nasal passages, and a sturdy body for endurance. ... For other uses, see Bloodhound (disambiguation). ... This article does not cite any references or sources. ...


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. Families 15, See classification A primate is any member of the biological order Primates, the group that contains all the species commonly related to the lemurs, monkeys, and apes, with the latter category including humans. ... Families Cercopithecidae Hylobatidae Hominidae Catarrhini is the unranked group of the Primates, one of the three major divisions of the suborder Haplorrhini. ... Suborders Mysticeti Odontoceti Archaeoceti (extinct) (see text for families) The order Cetacea (IPA: , L. cetus, whale) includes whales, dolphins and porpoises. ... Taste is one of the traditional five senses and refers to the ability to detect the flavor of foodstuffs and other substances (e. ... The Ring-tailed Lemur (Lemur catta) is a prosimian of the family Lemuridae. ... Binomial name Eulemur rubriventer (I. Geoffroy, 1850) The Red-bellied Lemur (Lemur rubriventer) is a medium sized prosimian with a luxuriant chestnut brown coat. ... Fanning honeybee exposes Nasonov gland (white-at tip of abdomen) releasing pheromone to entice swarm into an empty hive A pheromone is a chemical that triggers an innate behavioural response in another member of the same species. ... Binomial name Bombyx mori Linnaeus, 1758 For other senses of this word, see silkworm (disambiguation). ... Bombykol Many species use pheromone signals to direct essential behaviors such as mating, feeding, combat, flight, and nurturing the young. ...


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 hierarchy. 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. Insects display a wide variety of antennal shapes. ... Antennal Lobe is the deutocerebral neuropil of the insect which receive the input from the sensory neurons on the antenna. ... The mushroom bodies or corpora pedunculata are a pair of structures in the brain of insects and other arthropods. ... In the thoracic region, the postero-lateral part of the anterior column projects lateralward as a triangular field, which is named the lateral column (lateral cornu, lateral horn). ... An axon, or nerve fiber, is a long slender projection of a nerve cell, or neuron, which conducts electrical impulses away from the neurons cell body or soma. ...


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

See also

The Accessory olfactory system (AOS) is one of the two olfactory systems commonly found in vertebrates. ... Machine olfaction is the automated simulation of the sense of smell. ... Machine olfaction is the automated simulation of the sense of smell. ... It has been suggested that this article or section be merged with Anosmia. ... The limbic system (Latin limbus: border or edge) includes the structures in the human brain involved in emotion, motivation, and emotional association with memory. ...

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

  Results from FactBites:
 
Olfaction - SourceryForge (896 words)
Olfaction, the sense of smell, is the detection of chemicals dissolved in air (or, by animals that breathe water, in water).
As an exception among birds, olfaction is important in the tubenoses.
In many species olfaction is highly tuned to pheromones; a male silkworm moth, for example, can smell a single molecule of bombykol.
Olfaction - Wikipedia, the free encyclopedia (1574 words)
Olfaction (the sense of smell) is the detection of chemicals dissolved in air.
Olfaction is one of the five senses originally described by Aristotle.
In many species, olfaction is highly tuned to pheromones; a male silkworm moth, for example, can sense a single molecule of bombykol.
  More results at FactBites »

 
 

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