Physiology of smell and smell acuity
- Odor perception is mediated by the olfactory nerve.
- Olfactory receptor cells are neurons found in the olfactory epithelium.
- Odorous molecules bind to receptor proteins on cilia, initiating electric signals.
- Signals travel along olfactory nerves to the olfactory bulb in the brain.
- Olfactory information is processed in the olfactory cortex and forwarded to the central nervous system.
- Ability to identify odor varies among individuals and decreases with age.
- Women generally outperform men in odor discrimination, but studies show conflicting results.
- Pregnant women often have increased smell sensitivity.
- Sense of taste decreases with age as smell dominates.
- Chronic smell problems increase with age, particularly after 70 years old.
Smell acuity compared to other animals
- Humans have a good sense of smell despite having fewer olfactory receptor genes than mice.
- Smell can induce pleasure, warn of danger, locate mates, find food, and detect predators.
- Humans can distinguish approximately one trillion unique aromas.
- Flavorists and perfumers can identify discrete chemicals in complex mixtures using only smell.
- There has been an apparent evolutionary decline in the human sense of smell.
Habituation or adaptation
- Familiar odors, like body odor, are less noticeable due to habituation.
- Continuous odor exposure leads to fatigue, but the sense of smell recovers with stimulus removal.
- Odors can change depending on environmental conditions, such as cool dry air.
- Habituation affects the ability to distinguish odors and focuses on differences and changes.
- Mixing odorants can block the perception of habitual odorants and adjust sensitivity to differences.
Genetic component
- Thousands of olfactory receptor gene sequences are known.
- Olfactory receptors are seven-helix-turn transmembrane proteins.
- There is a conserved sequence in most olfactory receptors that serves as a metal-ion binding site.
- Copper is essential for the detection of certain odorants.
- The specific metal ion binding site in olfactory receptors is still under study.
Measuring techniques, concentration, perception, sampling, regulation, and control
- Sensory evaluation: Using human senses to detect and evaluate odor presence.
- Chemical analysis: Identifying and quantifying specific odor-causing compounds.
- Electronic noses: Instruments that mimic the human olfactory system to detect and analyze odors.
- Dynamic olfactometry: Measuring odor concentration by diluting the sample and determining the dilution ratio.
- Gas chromatography: Separating and analyzing odor compounds based on their chemical properties.
- Odor concentration refers to the pervasiveness of an odor.
- It can be measured using techniques like dilution and dynamic olfactometry.
- The concentration of odor-causing compounds determines the intensity of the odor.
- Different odor thresholds exist for various compounds, indicating the minimum concentration required for detection.
- High odor concentration can lead to annoyance, discomfort, and health issues.
- Odor perception varies among individuals due to genetic and environmental factors.
- The human nose can detect a wide range of odors, from pleasant to unpleasant.
- Odor perception can be influenced by factors like age, gender, and cultural background.
- The brain processes odor information in the olfactory cortex, contributing to the perception of smell.
- Perception of odor can trigger emotional and memory responses in individuals.
- Proper sampling techniques are crucial for accurate odor measurement.
- Sampling methods include grab sampling, passive sampling, and active sampling.
- Sample collection should consider factors like temperature, humidity, and airflow.
- Sampling locations should be representative of the odor source and its surrounding environment.
- Sampling frequency and duration depend on the variability and persistence of the odor.
- Odor regulations exist in many industries to minimize the impact of odors on the community.
- Regulatory agencies set odor standards and guidelines for different sectors.
- Odor control measures include source reduction, containment, and treatment.
- Technologies like biofilters, activated carbon filters, and chemical scrubbers are used for odor control.
- Continuous monitoring and periodic assessment help ensure compliance with odor regulations.
Odor Data Sources
Reference | URL |
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Glossary | https://www.alternix.com/blogs/glossary-of-terms/odor |
Wikipedia | http://en.wikipedia.org/wiki/Odor |
Wikidata | https://www.wikidata.org/wiki/Q485537 |
Knowledge Graph | https://www.google.com/search?kgmid=/m/01jqkv |