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Lecture 12

BGYB30H3 Lecture 12 Notes Sensory 3-Oct 20

Biological Sciences
Course Code
Ingrid L.Stefanovic

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BGYB30H3 Lecture 12 Notes
-olfaction is the system underlying how we sense and perceive odor
-the olfactory epithelium contains olfactory receptors/primary olfactory neurons
-primary olfactory neurons have free nerve endings and are found in the mucus membrane of
the nose
-primary olfactory neurons move through the olfactory tract to the olfactory bulb where they
synapse unto secondary olfactory neurons
-all sensory systems have support cells
-stem cells (basal cells) are located in the olfactory epithelium and replace dead olfactory
-olfactory bulb processes and integrates info from the primary olfactory neurons in the nose
-secondary olfactory neurons terminate in the olfactory cortex, which sends info to the
amygdala and the hippocampus (triggers emotional response and memory of the odor)
-odorant molecules dissolve and penetrate the mucus to bind to certain odorant receptors that
are sensitive to these molecules
-odorant receptors are GPC receptors that are linked to G-olfaction protein (increases cAMP)
-each olfactory cell contains different odorant receptors
-olfactory bulb integrates and decodes info about dominant smells from the primary olfactory
-the five main taste receptors of the gustatory (taste) system are salty (activated by the
presence of sodium ions), sour (activated by presence of hydrogen ions), bitter (seen as
potentially toxic), sweet (seen as nutritious), and umami (food containing glutamate)
-salty and sour receptors are linked to changes in homeostasis in the body
-sweet receptors are found at the tip of the tongue, salty receptors found behind, then sour
receptors, and bitter receptors near the end of the tongue
-taste receptors are found in taste buds found in clusters in on the tongue
-taste cells are non-neuronal polarized epithelial cells that move through the oral cavity of the
taste pore
-microvilli at the tip of taste cells increase surface area of the cell in contact with the
-when taste ligands bind to taste receptors, action potential is generated and conducted on the
primary gustatory sensory neuron
-each taste cell receives info about one particular taste
-taste cells for sour and salty molecules synapse with primary gustatory sensory neuron
through releasing serotonin
-taste cells for sweet, bitter, and umami release ATP to activate the primary gustatory sensory
neuron (non-traditional synapse)
-bitter, sweet, and umami receptors are GPCR and use G-gustducin protein
-sodium or hydrogen ions activate taste cell and intracellular activation of signaling pathways
-sweet, umami, and bitter receptors increase calcium in the receptor until ATP is released unto
the primary sensory neuron
-serotonin is released from salt and sour receptors onto primary sensory neurons
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