OPEN ACCESS | Published on : 26-Dec-2025 | Pages: 45-51 | Doi : 10.37446/edibook172024/45-51
Olfaction, also known as the sense of smell, is a chemosensory modality that is essential for taste, memory, emotion, and protective actions. It detects volatile chemicals in the environment. Olfactory epithelium is found in the roof of the nasal cavity and contains bipolar olfactory receptor neurons, supporting cells, and basal stem cells that can regenerate continuously. The olfactory epithelium is situated in such a location where the nervous system is directly connected with the external environment. Odorant molecules dissolves in the mucus layer and attach to certain receptors on olfactory neurons' cilia, start signal transduction through G-protein-mediated pathways that produce action potentials that are sent via the olfactory nerve. These inputs create synapses in the glomeruli of the olfactory bulb on mitral and tufted cells, whose axons travel to the piriform cortex, amygdala, and entorhinal cortex, among other key olfactory cortical areas, via the olfactory tract. Olfactory impulses, contrary to other sensory systems, do not require thalamic relay to reach the cortex, which facilitates quick emotional and memory-related reactions. Although sensitivity varies with stimulus parameters and exhibits rapid adaptation, humans are able to discriminate hundreds of odorants. Clinically, infections, age, trauma to the cribriform plate, neurodegeneration, or congenital abnormalities can cause olfactory dysfunctions such hyposmia and anosmia. To fully understand its functions in behavior, health, and illness, one must have an adequate knowledge of olfactory physiology.
Olfactory epithelium, Odorant receptors, Olfactory bulb, Signal transduction, Olfactory pathways Olfactory dysfunction (anosmia/hyposmia)
Amoore, J. E. (1970). Molecular basis of odor. Charles C. Thomas.
Bear, M. F., Connors, B. W., & Paradiso, M. A. (2015). Neuroscience: Exploring the Brain (4th ed.). Lippincott Williams & Wilkins.
Doty, R. L. (2015). The Neurology of Olfaction. Cambridge University Press.
Enokey. (n.d.). Anatomy of the olfactory system. Retrieved from https://entokey.com/anatomy-of-the-olfactory-system/
Ganong’s Review of Medical Physiology - Book 2 - Flip eBook Pages 1–50 | AnyFlip.
https://anyflip.com/rvtsv/oumi/basic
Kandel, E. R., Schwartz, J. H., & Jessell, T. M. (2000). Principles of Neural Science (4th ed.). McGraw-Hill.
Kondo, K., Kikuta, S., Ueha, R., Suzukawa, K., & Yamasoba, T. (2020). Age-related olfactory dysfunction: Epidemiology, pathophysiology, and clinical management. Frontiers in Aging Neuroscience.
Leffingwell, J. C. (2002). Olfaction: A review. Leffingwell Reports, 1(1), 1–24.
NIH. (n.d.). Sense of smell and taste. National Institute on Deafness and Other Communication Disorders. https://www.nidcd.nih.gov/
Pinel, J. P. J., & Barnes, S. J. (2018). Biopsychology (10th ed.). Pearson.
Purves, D., Augustine, G. J., Fitzpatrick, D., et al. (2018). Neuroscience (6th ed.). Oxford University Press.
Shipley, M. T., & Ennis, M. (1996). Functional organization of olfactory pathways. Journal of Neurobiology, 30(1), 123–176.
The New England Journal of Medicine. (n.d.). Structure of the olfactory epithelium [Figure]. Retrieved from https://www.nejm.org/doi/full/10.1056/NEJMoa022043.
