8 Taste & Smell Flashcards
What is the purpose of the chemosensory system?
Chemosensation is th eperception of chemicals. We detect chemicals through three different systems: taste, olfaction, and somatosensory. tase refers to the sensation arising from taste receptors and is used to evaluate the nutritious content of food and avoid ingestion of toxic substances. Smell is the detections of volatile odorants through olfactory and somatosensory systems. Olfaction is the perception of odorants through activation of odorant receptors, and is mediated by cranial nerve I. Smell is important for social interactions and memory. Trigeminal somatosensory fibers of CN V detect thermal, mechanical, and chemical stimuli in the head and neck, and initiate protective respiratory reflexes for noxious chemicals.
What are the consequences of taste or smell dysfunction?
What are the consequences of taste or smell dysfunction?
Chemosensation is an integral aspect of how we interact with the environment and guides our behavior. Loss of these senses can lead to hazardous situations, such as food poisoning and the inability to detect fire or gas. The disruption of appetitive cues can lead to weight changes and nutritional deficiencies. People without taste often lose the desire to eat and may require medical intervention to restore their appetite.
What is the impact of taste or smell dysfunction on quality of life?
What is the impact of taste or smell dysfunction on quality of life?
There is a well-established relationship between olfaction, emotion, and memory, in which odorants can strongly evoke emotions related to the previous experiences associated with that odor. Odor-associated memories are long-lasting and salient. The loss of chemosensation impairs the ability to feel motivated and engage in pleasurable activities, and is correlated with lower perception of quality of life, changes in mood, and depression.
Social chemical cues play a role in determining our social behavior. It has been shown that odorants are reported to influence mate selection and cause females to synchronize their menstrual cycle, indicating a biological importance for olfactory cues. Smell dysfunction can lead to impaired social interactions and social isolation.
What is the relationship between taste, smell, and flavor?
What is the relationship between taste, smell, and flavor?
The flavor of our food is the combination of taste, smell, and the somatosensory-mediated sensations of temperature, texture, and pungency. Thus, patients presenting with taste complaints may often really suffer from olfactory dysfunction.
Describe the trigeminal (CN V) contribution to smell.
The trigeminal system mediates the perception of touch, pressure, temperature, and nociception (pain or irritation), and displays a limited spectrum of sensations compared to olfaction. The ophthalmic and maxillary branches of the trigeminal nerve innervate the nasal cavity. Most odorants can activate the trigeminal system, and individuals with impaired olfaction (CN I) may still be able to detect odors (often strong irritating odors such as gasoline or ammonia) through trigeminal sensations.
Describe the trigeminal (CN V) contribution to smell.
The trigeminal system mediates the perception of touch, pressure, temperature, and nociception (pain or irritation), and displays a limited spectrum of sensations compared to olfaction. The ophthalmic and maxillary branches of the trigeminal nerve innervate the nasal cavity. Most odorants can activate the trigeminal system, and individuals with impaired olfaction (CN I) may still be able to detect odors (often strong irritating odors such as gasoline or ammonia) through trigeminal sensations.
What are the five basic tastes?
What are the five basic tastes?
Taste is limited to a spectrum of five tastes: salty, sour, sweet, bitter, and umami. Umami is the detection of L-amino acids and is also described as savory. Sweet is indicative of energy-rich foods. The detection of salt allows us to control proper dietary electrolytic balance. Sour and bitter are used to warn against noxious/poisonous compounds.
Where are taste receptors located?
Where are taste receptors located?
Taste receptors are located on taste receptor cells. Taste buds are bundles of taste receptor cells. Taste receptors are also found on specialized chemosensory cells, ciliated cells, and smooth muscle cells in the airway and are thought to mediate the perception of irritants. Taste-sensing of food also occurs within the gastrointestinal tract as taste receptors are expressed by enteroendocrine cells.
Where are taste buds located?
Where are taste buds located?
Taste buds are located on a large portion of the tongue dorsum within small protrusions of epithelium called papillae. Taste buds are also found on the soft palate, larynx, pharynx, and epiglottis, and these taste buds are innervated by the vagus nerve (CN X).
Describe the four types of papillae.
Describe the four types of papillae.
The anterior two-thirds of the tongue contains fungiform papillae. Fungiform papillae contain 1 to 15 taste buds each and are innervated by the chorda tympani branch of the facial nerve (CN VII). There are approximately 750 fungiform papillae.
The posterior aspects of the tongue contain circumvallate and foliatepapillae and are innervated by the glossopharyngeal nerve (CN IX). Humans have 8 to 12 circumvallate papillae arranged in a V-shape on the dorsal tongue and a few foliate papillae on the lateral sides, each housing dozens of taste buds.
Filiform papillae are distributed throughout the tongue dorsum. They contribute to the mechanical distribution of chemicals on the tongue, and do not contain taste buds.
Describe the central processing of taste.
Describe the central processing of taste.
Taste receptor cells transmit taste information to neural fibers within the taste bud, which project from neurons located in the sensory ganglia of cranial nerves VII, IX, and X. The cranial nerves enter the central nervous system at the brainstem and converge to form the solitary tract. Afferent information enters the thalamus and proceeds to the gustatory cortex.
Where is olfactory epithelium found?
Where is olfactory epithelium found?
The olfactory epithelium is located in the superior and posterior aspect of the nasal cavity, including the nasal septum and superior and middle turbinates. The precise location of the olfactory epithelium varies between individuals.
Describe the cellular composition of the olfactory epithelium.
Describe the cellular composition of the olfactory epithelium.
The olfactory epithelium is a pseudostratified columnar epithelial tissue comprised of several cell types. Bipolar sensory neurons extend an apical dendrite to the epithelial surface from which cilia extend to detect odors. The basal pole extends into an axon, which crosses the cribriform plate and enters the olfactory bulb. The axons of the sensory neurons are ensheathed by olfactory ensheathing cells, which have received clinical interest for their ability to support axon growth.Basal cells produce new olfactory sensory neurons as the old neurons die or are damaged. Supporting or sustentacular cells regulate and maintain the mucus layer into which odorants dissolve. Flask-shapedmicrovillar cells have no known role, but can respond to odorants and may play a role in reception.
Where are olfactory receptors located?
Where are olfactory receptors located?
We are able to distinguish over 1,000 odorants through a large multigene family of receptors that detect specific chemical structures within odorant molecules. Olfactory receptors are located on the cilia of bipolar sensory neurons within the olfactory epithelium. Each sensory neuron expresses only one type of receptor.
Describe the central processing of olfactory stimuli.
Describe the central processing of olfactory stimuli.
Odorant molecules that enter the nasal cavity and diffuse through the mucus layer bind to specific odorant receptors depending on their chemical structure. Odor-evoked responses are conducted through the sensory neuron axons, which converge with axons expressing the same receptor type into circular structures called glomeruli in the olfactory bulb. Information about the odorant is encoded by the pattern of sensory neurons and the glomeruli they activate forming a chemotopic map. Second-order neurons (mitral and tufted cells) transmit the response through the olfactory tract to regions in the frontal lobe and dorsomedial temporal lobe. There is a structural overlap of olfactory-responsive regions and those related to emotion, memory, and motivation. These regions include the amygdala, entorhinal cortex, orbital cortex, striatum, hypothalamus, and hippocampus. The structural overlap is thought to contribute to the salience of olfactory memories and emotional responses.
What are the terms used to describe olfactory dysfunction?
What are the terms used to describe olfactory dysfunction?
Anosmia is the absence of olfactory function. Hyposmia describes reduced olfactory function. Dysosmias are changes in odor quality, including parosmia (altered perception of an odor) and phantosmia(perception of an odor when that odor is not present).
