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12 Cards in this Set
- Front
- Back
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Olfactory system |
Olfaction (smell), is intimately linked with taste. Heavily linked to memory and recognition, Allows us to develop associations between objects in the world and expected smells. Allows us to distinguish food that may have gone bad. |
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Neural coding of olfactory signals |
Smell receptors reside in the olfactory mucosa, covered by mucus. Chemical odorants attach to cilia of olfactory receptors (hair cells). Each olfactory receptor is sensitive to only a narrow range of odorants. 350 different types of olfactory receptors in humans, each receptor responds to a different group of odorants. |
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Activating olfactory receptor neurons |
Human olfactory mucosa contains approx 350 different kinds of receptor neurons. about 10,000 of each type. each type synapses with a specific glomerulus. |
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Spatial coding of odors in glomeruli |
Different chemical odorant groups activate glomeruli on different parts of the olfactory bulb. Spatial place coding: evidence for an 'olfactotropic map'?. The layout of glomeruli is very similar within members of a species. |
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The olfactory pathway |
Olfactory bulb projects directly to pyriform cortex and the amygdala. Primary olfactory cortex. Affective component. Also projects to orbitofrontal cortex via the medial dorsal (MD) nucleus. |
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Anosmia |
The inability to identify smells following shearing of the olfactory bulbs or orbitofrontal cortex. |
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The Gustatory (taste) system |
The functions of taste are similar to that of olfaction, allows us to distinguish between foods that are good and bad, strong ties to memory, can be altered with experience. Certain tastes are indicative of nutritional value or potential danger. The presence of sugars are important for signalling caloric value. Salty tastes usually indicate sodium which is important for electrolytes. Bitterness can be an indicator of poison. |
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5 main qualities of taste |
Bitterness, sourness, sweetness, saltiness, and unami (savory, MSG). |
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Neural coding of taste |
Each taste bus contains 50-100 taste cells, about 10,000 taste buds. Transduction occurs when chemicals in our saliva contact receptor sites located on the taste cells. Action potentials are sent from the axons of taste cells to three different cranial nerves. |
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The taste pathway |
APs from taste cells are transmitted via cranial nerves 7,9, and 10. Facial (7), Glossopharyngeal (9), and Vagus (10). Taste information arrives in the ventral posterior medial (VPM) nucleus of the thalamus. Signal is sent to both primary (S1) and secondary (S2) sensory association cortices, insular cortex (taste centre), Orbitofrontal cortex. |
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Ageusia |
Inability to recognize common tastes. Can occur following ear injury (cranial nerve 7 runs through the middle ear). |
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Physiology of flavour perception |
The OFC receives inputs from multiple sensory systems and contains many different kinds of bimodal neurons. OFC may help us link a particular flavor with a specific object so we learn which foods are good to eat. Neurons in the OFC will respond to specific foods when hungry, but the same neurons stop firing when we are satiated. |
