Mary Lynn, Kyle, Cameron, Jack, Andrew, Izzy Taste and Smell Mary Lynn, Kyle, Cameron, Jack, Andrew, Izzy
Objectives Discuss sensory processes including specific nature of energy transduction, relevant anatomical structures, and specialized pathways in the brain for taste and smell Explain common sensory disorders in relation to smell and taste Identify the four basic tastes Discuss the differences among the taste, smell, and flavor
Essential Questions How do smell and taste work? (Background info) What is the nature of energy transduction? What are some important anatomical structures involved in smell and taste? What causes loss of smell and taste? What are common smell and taste disorders? What are the four basic tastes? What are the differences between smell, taste, and flavor? What are the similarities between smell and taste?
How tasting works Taste sensory cells (found in taste buds): Odor and food molecules activate membrane receptors Taste signals go to the limbic system and cerebral cortex Patterns of nerve activity encode taste sensations Sensory processing allows us to interpret flavors Genes determine the kinds of taste receptors we have, and experiences shape our perceptions Taste disorders may be genetic, or may result from illness or injury Taste preference: infants have heightened taste sensitivity while elders have decreased ability to taste Sensory interaction: taste receptors easily damaged by alcohol, smoke, acids, or hot foods but gustatory receptors are frequently replaced Supertasters are those ppl with taste buds for bitter flavors, experiences sense of taste with far greater intensity. Nontasters: person unable to taste the chemical phenylthiocarbamide Sensations of flavor and aroma often work together, especially during eating
How SmeLL Works Smell: chemical sense detected by sensory cells called chemoreceptors. odorant stimulates chemoreceptors in the nose that detect smellthey pass on electrical impulses to the brainbrain interprets patterns in electrical activity as specific odors and olfactory sensation becomes perception -- something we can recognize as smell The olfactory bulb in the brain, which sorts sensation into perception, is part of the limbic system. This link to brain's emotional center links smell to memories, feelings, and emotions can bring on a flood of memories, influence people's moods and even affect their work performance. Used as a form of communication: chemical signals released by organisms to communicate with other members of their species (pheromones) Scent Marketing: sellers use scents to set a mood and sell their product. Similar to Aromatherapy, which is the use of selected fragrances in lotions and inhalants to affect mood and promote health
Sensory Processes (nature of energy transduction) (Energy transduction) Olfactory: Odors reach the receptor (Receptor in this case is the nose) Odor molecule reaches receptor proteins associated with specialized hairs in the nose. The nerves that are associated with smell send information about the stimulus to the brain’s olfactory bulbs. (Specialized pathways) The fact that olfaction is not relayed through the thalamus and instead goes directly to the olfactory bulbs suggests that the olfactory sense is more evolved that other sensations.
Important anatomical structures and specialized pathways in the brain (Taste) Taste sensory cells are found in taste buds Papillae: cluster of small mucous-membrane projections. All over their surfaces are taste buds: made up of taste sensory cells Taste buds are “taste pores”: where food and drink molecules come in fitting into membrane receptors located on small finger-like protrusions called microvilli at the tops of taste sensory cells Microvilli: tiny hair-like folds in the plasma membrane that extend from the surface of many absorptive or sensory cells. Increase surface area of the cells. Taste signals go to the limbic system and cerebral cortex Limbic System: hippocampus, hypothalamus and amygdala Emotional tastes (pleasant, nostalgic, etc.) and memory function Cerebral Cortex Identification of tastes
A taste sensory cell and the five types of taste receptors A taste sensory cell and the five types of taste receptors. Flavor molecules fit into receptors on the microvilli at the top of the cell, causing electrical changes that release transmitter onto the nerve ending at the bottom of the cell. The nerve carries taste messages to the brain.
Taste Signals in the Limbic system and cerebral cortex
Important anatomical structures and specialized pathways in the brain (Smell) Olfactory Epithileum: Mucus in the nose Stimuli are volatile chemical substances that can evaporate and be carried in the air, Mucus dissolves these stimuli Olfactory Cilia: Nose Hair Receptors for smell Hair like structures in the upper portions of the nasal passages, constantly being replaced Olfactory Bulb Neural impulses are routed through here and then sent to Olfactory Cortex Temporal Lobe Olfactory cortex is in the temporal lobe Smell is the only sensory input not routed through Thalamus
VISUAL AID
What Causes a loss of smell and taste? Age Genetics Tobacco smoking Respiratory infections, sinus cavities, etc.
Common sensory disorders Taste Phantom Taste Perception: Most common, it’s a lingering, often unpleasant taste even though you have nothing in your mouth. Hypogeusia: reduced ability to taste sweet, sour, bitter, salty, and umami Ageusia: inability to detect any tastes (rare) Dysgeusia: a foul, salty, rancid, or metallic taste sensation will persist in the mouth. Most often, people are experiencing a loss of smell as opposed to a loss of taste. Smell Hyposmia: reduced ability to detect odors. Anosmia: inability to detect odors at all. People who experience smell disorders either have a loss in their ability to smell or changes in the way they perceive odors.
Four Basic Tastes The sense of taste (gustation) have been isolated in laboratory experiments to show these four qualities Sweet Sour Bitter Salty Recently researchers have found a fifth taste quality called umami that is associated with monosodium glutamate.
Differences between taste, smell, and flavor Smell (olfaction) Chemical Olfactory receptor cells respond to odors and aromas Sense of taste depends upon sense of smell Taste (gustation) Interaction between our chemical senses Four (or five) flavors: sweet, sour, salt, bitter, umami Chemical, simply five pieces of information Flavor Flavor=taste+smell, combination of senses Taste identification is impaired without smell Mental construct that can’t doesn’t exist outside of our mind, infinite
Similarities/Connections between taste and smell The complicated process of smelling and tasting begins when molecules released by the substances around us stimulate special nerve cells in the nose, mouth, or throat. These cells transmit messages to the brain, where specific smells or tastes are identified. Both olfaction (smell) and gustation (taste) depend upon a dissolved sample of chemical compound fitting into a receptor cell, like a key fits into a lock. Many flavors are recognized through the sense of smell. Taste and smell cells are the only cells in the nervous system that are replaced when they become old or damaged.
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