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Questions and Answers
What is the physiological process that begins when an odorant binds to a G-protein-coupled receptor in the olfactory epithelium?
What is the physiological process that begins when an odorant binds to a G-protein-coupled receptor in the olfactory epithelium?
Which of the following structures houses the first synapse in the olfactory pathway?
Which of the following structures houses the first synapse in the olfactory pathway?
What is the primary function of the olfactory glands located in the lamina propria?
What is the primary function of the olfactory glands located in the lamina propria?
Which of the following statements is TRUE regarding olfactory receptor neurons?
Which of the following statements is TRUE regarding olfactory receptor neurons?
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Which of the following brain regions is NOT involved in processing olfactory information?
Which of the following brain regions is NOT involved in processing olfactory information?
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What is the primary reason why dogs have a more acute sense of smell than humans?
What is the primary reason why dogs have a more acute sense of smell than humans?
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Which of the following structures are found on the surface of the tongue and contain taste buds?
Which of the following structures are found on the surface of the tongue and contain taste buds?
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How many different types of gustatory receptors (taste receptors) are there?
How many different types of gustatory receptors (taste receptors) are there?
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Which of the following statements is FALSE regarding olfactory and gustatory receptors?
Which of the following statements is FALSE regarding olfactory and gustatory receptors?
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What would be the most likely consequence of damage to the cribriform plate of the ethmoid bone?
What would be the most likely consequence of damage to the cribriform plate of the ethmoid bone?
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Study Notes
Special Senses: Olfaction
- Olfaction (smell) is a special sense involving olfactory receptors that respond to airborne chemical stimuli.
- Olfactory organs are located in the nasal cavity, on either side or the nasal septum, composed of two layers: olfactory epithelium and lamina propria.
- Olfactory epithelium contains olfactory sensory neurons, highly modified nerve cells that detect dissolved chemicals interacting with odorant-binding proteins. It also has supporting and basal epithelial cells (stem cells).
- Lamina propria contains areolar tissue, blood vessels, and nerves, as well as olfactory glands that secrete mucus.
- Olfactory reception involves odorant binding to G-protein-coupled receptors, creating a generator potential (depolarization).
- Afferent fibers from the olfactory epithelium collect into bundles, penetrate the cribriform plate of the ethmoid bone, and reach the olfactory bulbs of the cerebrum where the first synapse occurs.
- Axons leaving the olfactory bulb travel along the olfactory tract to the olfactory cortex (temporal lobe), hypothalamus, and limbic system. Olfactory information is the only type of sensory information that reaches the cerebral cortex directly, bypassing the thalamus.
- Humans can distinguish thousands of chemical stimuli. Dogs have significantly greater olfactory receptor surface area (72 times more) leading to a vastly superior sense of smell.
- Olfactory receptors are frequently replaced; however, total receptor numbers decline with age.
Special Senses: Gustation
- Gustation (taste) provides information about food and liquids consumed.
- Gustatory epithelial cells (taste receptors) are distributed on the superior surface of the tongue and portions of the pharynx and larynx, found within taste buds. Taste buds are associated with lingual papillae.
- There are four types of lingual papillae: filiform, fungiform, vallate (circumvallate), and foliate. Filiform papillae do not contain taste buds; fungiform contain approximately 5; vallate papillae can have as many as 100; and foliate contain taste buds, but all of them contain basal epithelial cells (stem cells).
- Gustatory epithelial cells extend microvilli through taste pores and are replaced every 10 days.
- They are innervated by cranial nerves that synapse, via the solitary nucleus of the medulla oblongata, to the thalamus and gustatory complex of the insula.
- There are four primary taste sensations: sweet, sour, salty, and bitter. Additional sensations might exist including umami (savory, glutamate), and water.
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Description
Dive into the intriguing world of olfaction, the sense of smell. Learn about the anatomy of olfactory organs, the function of olfactory epithelium, and the biochemical processes that enable our sense of smell. This quiz will test your knowledge on the structure and function of this essential special sense.
