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
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