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Retronasal Olfaction
Published in Alan R. Hirsch, Nutrition and Sensation, 2023
Jason J. Gruss, Alan R. Hirsch
Olfaction is the process by which chemical stimulants are processed into the sensation of smell. In this, aerosolized chemical stimulants traverse the nose, move into the olfactory cleft, and eventually contact the olfactory sensory neurons. With a sufficient stimulus, the sensory signal of smell is triggered. This is considered a chemosensory process, as the stimulus is a chemical that binds to a receptor. Most of the other human senses use different stimuli. Vision uses light; hearing uses sound waves; touch uses pressure. All of those sources are not from a chemical stimulus. Using chemicals to stimulate a response is known as chemosensation. Olfaction shares chemosensation with the sense of taste. Smell and taste are strongly linked in this regard. In fact, 90% of taste, or flavor, is actually smell (Hirsch 1992a). Despite the close association, there are significant differences between smell and taste.
The Special Sense Organs and Their Disorders
Published in Walter F. Stanaszek, Mary J. Stanaszek, Robert J. Holt, Steven Strauss, Understanding Medical Terms, 2020
Walter F. Stanaszek, Mary J. Stanaszek, Robert J. Holt, Steven Strauss
The sense of smell is termed olfaction, osmesis, or osphresis. The olfactory receptor cells (neurons) are located high in the roof of the nasal cavity in the olfactory epithelium consisting of receptor cells, sustentacular or supporting cells, and basal cells. These neurons end in a bulbous olfactory vesicle or sac from which extend cilia that project through the fluid covering the surface epithelium. The olfactory bulbs connect olfactory nerve fibers to axons of neurons projecting into the olfactory area of the brain (Figure 13.1).
Chemosensation
Published in Emily Crews Splane, Neil E. Rowland, Anaya Mitra, Psychology of Eating, 2019
Emily Crews Splane, Neil E. Rowland, Anaya Mitra
Taste and smell are closely interrelated; when we talk about different tastes (strawberry, lemon, etc.), we often mean odors in combination with taste. This combination is called flavor and will be discussed in Chapter 6. Taste (without flavor) is vitally important for detection and recognition of the many food components that have little or no odor (e.g., salt). Unlike olfaction, for which there are hundreds of receptors, the number of receptor types involved in taste is far fewer and they are organized into discrete classes of sensation. Only some of the taste receptors belong to the GPCR superfamily; others are ion channels.
Analyses on the influence of normal nasal morphological variations on odorant transport to the olfactory cleft
Published in Inhalation Toxicology, 2022
Ryan M. Sicard, Reanna Shah, Dennis O. Frank-Ito
Olfaction is the sensation arising from the nasal cavity following stimulation of the olfactory receptors by odorant molecules. Olfactory dysfunction is characterized by reduced or absent sense of smell, ranging from hyposmia to anosmia (Guss et al. 2009). While olfactory perception is effective when the combination of sensorineural components and conductive factors function properly, the role of conductive factors (respiratory effort and nasal anatomical structure) in olfaction has been given less attention. The nasal cavity plays an essential role in odor perception, which consists of the transportation of volatile chemical molecules via airflow to the olfactory receptors (Zhao et al. 2004). In order to completely understand human olfaction, it is crucial to gain knowledge of the airflow patterns in the human nasal cavity and quantify the transport of odorant-laden air to the olfactory region.
Potential neurological manifestations of COVID-19: a narrative review
Published in Postgraduate Medicine, 2022
Joseph V. Pergolizzi, Robert B. Raffa, Giustino Varrassi, Peter Magnusson, Jo Ann LeQuang, Antonella Paladini, Robert Taylor, Charles Wollmuth, Frank Breve, Maninder Chopra, Rohit Nalamasu, Paul J. Christo
Neurological sequelae of SARS have been only sporadically reported. Acute olfactory neuropathy has been reported in a case study of a 27-year-old female SARS patient who was diagnosed with SARS in 2003, hospitalized, and recovered with combination therapy of antiviral therapy (ribivarin plus steroids) [43]. Fever persisted for about three weeks from onset of symptoms. She was discharged from the hospital at around the same time she reported the paroxysmal bilateral loss of her sense of smell. An otolaryngologic examination, biochemistry tests, and subsequent magnetic resonance imaging scans showed nothing unusual with no lesions that might account for her loss of olfaction. Now 2 years after her recovery from SARS, she still has not regained her sense of smell [43]. The common causes of anosmia include structural defects in the nasal cavity or sinuses, head injury, brain trauma, brain lesions, or drug-induced loss of olfaction, and in her case, these could all be ruled out. It was postulated that her anosmia was a coronavirus-induced form of olfactory neuropathy [43].
Loss of smell in patients with traumatic brain injury is associated with neuropsychiatric behavioral alterations
Published in Brain Injury, 2021
Cristobal Langdon, Sara Laxe, Eduardo Lehrer, Joan Berenguer, Isam Alobid, Llorenç Quintó, Franklin Mariño-Sánchez, Montserrat Bernabeu, Concepció Marin, Joaquim Mullol
In patients with a TBI and olfactory dysfunction, depression is one of the most common outcomes (33). This is because certain brain areas involved in olfactory perception also govern the etiology of depression; in trauma, olfactory input is altered in the olfactory areas of the brain via the amygdala and the limbic system, causing depression directly (33,34). In addition, a reduced quality of life due to smell loss indirectly results in depression (33). Depression has been found to occur more frequently with frontal and temporal lobe lesions and left anterior lesions (35). In agreement with these studies, our study detected an increased level of depressive symptom scores in patients with a TBI and OD compared to patients with NOD. An increased level of depression can have several serious side effects including sleep disturbances and often insomnia, fatigue, general irritability and apathy, a disinterest in life activities, and even suicidal attempts. Furthermore, our results show that olfactory dysfunction appears to correlate with an enhanced level of anxiety similar to findings in previous studies (36). This may be explained by the fact that olfaction serves as a warning signal for imminent dangers such as a gas leakage, fire, poisonous fumes, spoiled food, etc., and a patient with smell loss would suffer from increased anxiety over the inability to protect themselves and their family from such hazards (8).