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A&P Lecture Test #4 (Olfaction and Gustation)
Terms in this set (31)
a) occurs through special senses (within head; also have special organ)
b) exteroceptors (sense stimuli from external environment)
c) chemoreceptors (sensitive to chemicals)
What are some things that characterize taste and smell detection?
-detection of odorants dissolved in the air
-provides information about food, people, danger
-we can distinguish 1000s of different odors
-volatile molecules (easily vaporized)
-dissolved in nasal mucus and are detected by chemoreceptors
1) mucus layer
-traps odor molecules
2) olfactory epithelium
-in nasal cavity
3) lammina propria
(then cribriform plate and olfactory bulb)
What are the 3 layers of the olfactory epithelium from bottom to top?
-sensory receptor organ
-located in superior region of nasa cavity
-surface of cribriform plate and nasal conchae of ethmoid
-has axon, cell body, and dendrite of OLFACTORY RECEPTOR CELL
-aerolar CT layer internal to olfactory epithelium
-houses blood vessels, servers, and olfactory glands
-olfactory glands = help form mucus covering the olfactory epithelium
Do the rejuvenation and sensitivity of receptors decline with aging?
1) olfactory receptor cells
2) supporting cells
3) basal cells
-like stem cells
-will replace the old olfactory cells every 40-60 days
what are the 3 olfactory epithelial cells and functions?
olfactory receptor cells
-primary neurons in sensory pathway for smell
-bipolar structure: a single dendrite sand unmyelinated axon
-olfactory hairs- cilia projecting from dendrites; house chemoreceptors for a specific odorant
-perceived smell depends on which cells ares stimulated
-about 400 receptors in nose
the combination of different olfactory receptors
-perceived smell depends on which cells are stimulated
What gives the perception of scent?
1) olfactory nerve
2) olfactory bulbs
3) olfactory tracts
What are the main components of the olfactory pathway?
olfactory nerves (CNI)
-bundles of olfactory axons
-project through skull' cribriform plate and enter the olfactory bulb
-relays sensory data to the brain and is responsible do the sense of smell
-ends of olfactory tracts located under the brain's frontal lobes
-this is where olfactory nerve fibers SYNAPSE with the secondary neurons
-axon bundles of secondary neurons on inferior frontal lobe surface
-project directly to primary olfactory cortex (in temporal lobe)
-sniff repeatedly or breathe deeply
-mucus contains OLFACTORY-BINDING PROTEINS
-olfactory sensations begin when odorant binds to proteins and protein stimulates receptor cells
-secondary neuron conducts signal to cerebral cortex
How does one detect smell?
-sense of taste
-detection of tastants (molecules and ions)
-the neuroepithelial chemoreceptors within taste buds
-on tongue and sold palate
-also have mechanoreceptors and thermoreceptors on tongue
a) gustatory microvillus
-forms dendritic ending
b) taste pore
-where the microvillus extends through; then extends to tongue surface
-dissolve in saliva and stimulate microvillus
What comprises gustatory cells?
-onion shaped organs that house taste receptors
-have gustatory cells
1) gustatory cells
-receptors cells that detect tastants
-live 7-9 days
2) supporting cells
-sustain gustatory cells
3) basal cells
-neural stem cells that replace gustatory cells
What are the 3 cells of taste buds?
what houses taste buds?
1) filiform papillae
2) fungiform papillae
3) foliate papillae
4) vallate (circumvallate) papillae
What are the 4 papillae of the tongue?
(1) filiform papillae
-helps with manipulation of food in the mouth
-NO TASTE BUDS
-on anterios 2/3rds of tongue
(2) fungiform papillae
-each contains a few taste buds
-on tip and sides of tongue
(3) foliate papillae
-not well-developed (don't work throughout life-time)
-houses taste buds in early childhood
-in lateral posterior or edges of tongue
(4) vallate (circumvallate) papillae
-largest and least numerous
-contains the MOST taste buds
-on posterior (backside) of tongue
-10-20 in a row
gustatory cells >> medulla >> thalamus >> gustatory cortex
what is the taste pathway (basic)?
1) primary neuron in cranial nerve brings signal to nucleus within the MEDULLA
-medullary activity triggers salivation and stomach secretions
-nauseating stimuli instead trigger gag or vomiting
2) signal is relayed to THALAMUS
3) it's then relied to PRIMARY GUSTATORY CORTEX in the cerebrum for conscious taste
-tate is integrated with temp, texture, and esp SMELL
-food has less taste if olfaction is blocked (i.e. having a cold)
What is the taste pathway (detailed)?
-produced by organic compounds
-sugar or artificial sweetner
-produced by metal ions
Na+ and K+
-associated with acids
-produced by alkaloids
-taste related to AAs produced by meaty flavor
What are the 5 tastes?
-for sweet, bitter, and unami = the tastants are MOLECULES
-tastant binds to specific cell membrane receptor...
....G protein is activated causing formation of 2nd messenger...
...results in cell depolarization
-for sale and sour = the tastants are IONS
-the tasting depolarizes the cell directly
What is the TRANSDUCTION in gustatory cells?
-Miraculin is a taste modifier, a glycoprotein extracted from the fruit of Synsepalum dulcificum
-the protein binds to the sweetness receptors. This causes normally-sour-tasting acidic foods, such as citrus to be perceived as sweet.
-The effect lasts up to about an hour
-binds the sweet receptor but does not activate (so there is no sweet
taste at first)
-but at a lower pH
(in sour or acidic environments),
the receptor changes its shape
so that miraculin can bind directly on the sweet
receptor site and elicits a sweet taste
what is miraculin and what is its mechanism?
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