Olfaction

olfactorysmellsense of smellodorlessaccessory olfactory systemsmellingolfactory senseolfactory lobescentsmells
Olfaction is a chemoreception that forms the sense of smell.wikipedia
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Sense

sensesfive sensessensory
Olfaction is a chemoreception that forms the sense of smell.
Sight (vision, visual sense), hearing (audition, auditory sense), taste (gustation, gustatory sense), smell (olfaction, olfactory sense), and touch (somatosensation, somatosensory sense) are the five traditionally recognized senses.

Flavor

flavoringflavourflavouring
It integrates with other senses to form the sense of flavor.
Flavor (American English) or flavour (British English; see spelling differences) is the sensory impression of food or other substances, and is determined primarily by the chemical senses of taste and smell.

Aroma compound

fragrancefragrancesodorant
Olfaction occurs when odorants bind to specific sites on olfactory receptors located in the nasal cavity.
Flavors affect both the sense of taste and smell, whereas fragrances affect only smell.

Olfactory bulb

olfactory bulbsolfactory lobesolfactory lobe
Glomeruli aggregate signals from these receptors and transmit them to the olfactory bulb, where the sensory input will start to interact with parts of the brain responsible for smell identification, memory, and emotion. These nerve fibers, lacking myelin sheaths, pass to the olfactory bulb of the brain through perforations in the cribriform plate, which in turn projects olfactory information to the olfactory cortex and other areas.
The olfactory bulb (Latin: bulbus olfactorius) is a neural structure of the vertebrate forebrain involved in olfaction, the sense of smell.

Retronasal smell

Often, land organisms will have separate olfaction systems for smell and taste (orthonasal smell and retronasal smell), but water-dwelling organisms usually have only one system.
Retronasal smell, retronasal olfaction, or mouth smell, is the ability to perceive flavor dimensions of foods and drinks.

Stimulus modality

sensory modalitiesmodalitysensory modality
Early scientific study of olfaction includes the extensive doctoral dissertation of Eleanor Gamble, published in 1898, which compared olfactory to other stimulus modalities, and implied that smell had a lower intensity discrimination.
Some sensory modalities include: light, sound, temperature, taste, pressure, and smell.

Olfactory receptor

olfactory receptorsodorant receptorodorant receptors
Olfaction occurs when odorants bind to specific sites on olfactory receptors located in the nasal cavity.
Olfactory receptors (ORs), also known as odorant receptors, are expressed in the cell membranes of olfactory receptor neurons and are responsible for the detection of odorants (i.e., compounds that have an odor) which give rise to the sense of smell.

Olfactory epithelium

dendritic knobepitheliumolfactory neuroepithelium
In vertebrates, smells are sensed by olfactory sensory neurons in the olfactory epithelium.
The olfactory epithelium is a specialized epithellial tissue inside the nasal cavity that is involved in smell.

Cyclic nucleotide–gated ion channel

Cyclic nucleotide-gated ion channelCNGCyclic nucleotide-gated channels
cAMP, which is the second messenger here, opens a cyclic nucleotide-gated ion channel (CNG), producing an influx of cations (largely Ca 2+ with some Na + ) into the cell, slightly depolarising it.
CNG channels are significant in the function of various sensory pathways including vision and olfaction, as well as in other key cellular functions such as hormone release and chemotaxis.

Olfactory nerve

olfactory nervesCN IOlfactory
Olfactory sensory neurons project axons to the brain within the olfactory nerve, (cranial nerveI).
The olfactory nerve is typically considered the first cranial nerve, or simply CN I, that contains sensory nerve fibers relating to smell.

Lateral inhibition

inhibitorynearby are depressed
There are also considerable similarities in the immediate processing of stimuli by lateral inhibition.
It is also referred to as lateral antagonism and occurs primarily in visual processes, but also in tactile, auditory, and even olfactory processing.

Olfactory system

olfactory cortexolfactorymain olfactory system
These nerve fibers, lacking myelin sheaths, pass to the olfactory bulb of the brain through perforations in the cribriform plate, which in turn projects olfactory information to the olfactory cortex and other areas.
The olfactory system, or sense of smell, is the sensory system used for smelling (olfaction).

Pheromone

pheromonespheromonalalarm pheromone
Olfaction has many purposes, such as the detection of hazards, pheromones, and food.
In reptiles, amphibia and non-primate mammals pheromones are detected by regular olfactory membranes, and also by the vomeronasal organ (VNO), or Jacobson's organ, which lies at the base of the nasal septum between the nose and mouth and is the first stage of the accessory olfactory system.

Nasal cavity

nasal cavitiesnasal passagenasal
Olfaction occurs when odorants bind to specific sites on olfactory receptors located in the nasal cavity.
Innervation of the nasal cavity responsible for the sense of smell is via the olfactory nerve, which sends microscopic fibers from the olfactory bulb through the cribriform plate to reach the top of the nasal cavity.

Odor

aromascentodour
Mitral cells, located in the inner layer of the olfactory bulb, form synapses with the axons of the sensory neurons within glomeruli and send the information about the odor to other parts of the olfactory system, where multiple signals may be processed to form a synthesized olfactory perception.
An odor, or odour, is caused by one or more volatilized chemical compounds that are generally found in low concentrations that humans and animals can perceive by their sense of smell.

Emotion

emotionsemotionalemotional state
Glomeruli aggregate signals from these receptors and transmit them to the olfactory bulb, where the sensory input will start to interact with parts of the brain responsible for smell identification, memory, and emotion.
With the arrival of night-active mammals, smell replaced vision as the dominant sense, and a different way of responding arose from the olfactory sense, which is proposed to have developed into mammalian emotion and emotional memory.

Brain

brain functionmammalian braincerebral
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).

Action potential

action potentialsnerve impulsenerve impulses
The binding of the ligand (odor molecule or odorant) to the receptor leads to an action potential in the receptor neuron, via a second messenger pathway, depending on the organism.
Some examples in humans include the olfactory receptor neuron and Meissner's corpuscle, which are critical for the sense of smell and touch, respectively.

Electro-olfactography

electro-olfactogramElectroolfactography
In vertebrates, responses to an odor can be measured by an electro-olfactogram or through calcium imaging of receptor neuron terminals in the olfactory bulb.
Electro-olfactography or electroolfactography (EOG) is a type of electrography (electrophysiologic test) that aids the study of olfaction (the sense of smell).

Piriform cortex

pyriform cortexolfactory cortexpiriform
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 function of the piriform cortex relates to the sense of smell.

Vomeronasal organ

Jacobson's organvomeronasalVomeronasal system
In the accessory olfactory system, stimuli are detected by the vomeronasal organ, located in the vomer, between the nose and the mouth.
The vomeronasal organ (VNO), or Jacobson's organ, is the paired auxiliary olfactory (smell) sense organ located in the soft tissue of the nasal septum, in the nasal cavity just above the roof of the mouth (the hard palate).

Limbic system

limbiclimbic structureslimbic region
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.
It supports a variety of functions including emotion, behavior, motivation, long-term memory, and olfaction.

Chemoreceptor

chemoreceptorschemoreceptionchemosensory
Olfaction is a chemoreception that forms the sense of smell.

Docking theory of olfaction

Shape theory of olfactionshape theory
According to the shape theory, each receptor detects a feature of the odor molecule.
While Turin comments that Block used "cells in a dish rather than within whole organisms" and that "expressing an olfactory receptor in human embryonic kidney cells doesn't adequately reconstitute the complex nature of olfaction..."

Electroantennography

electroantennogram
In insects, one can perform electroantennography or calcium imaging within the olfactory bulb.
It is commonly used in electrophysiology while studying the function of the olfactory pathway in insects.