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36 Cards in this Set
- Front
- Back
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Where is the olfactory epithelium located?
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Dorsal posterior recess of nasal cavity, immediately below cribriform plate
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What is the pathway from 1st --> 2nd order neurons inthe olfactory tract?
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Axons of neurosensory cells --> fenestrations in cribiform plate --> synapse in glomeruli w/ second order neurons (mitral and tufted cells) in olfactory bulb
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What is the nature of synapse on second order neurons?
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Strongly convergent in glomerulus
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What is the pathway from 2nd order neurons --> brain?
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Mitral cell axons --> lateral olfactory tract --> neurons of olfactory cortex and amygdala
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Where is the lateral olfactory cortex?
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Ventromedial temporal lobe (pyriform cortex)
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What are the targets of secondary projections from the primary olfactory cortex?
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Thalamus, hypothalamus, and hippocampus
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What are two things lining the surface of olfactory receptor cells?
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1. Fine olfactory cilia on epithelial surface
2. Embedded in mucous film |
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What secretes mucous?
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Bowman's glands in epithelium
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What is odorant binding protein? What does it do?
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In mucous, binds wide range of odorant molecules
May present odorants to olfactory receptors |
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How are receptor cells different from other neurons in the olfactory epithelium?
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Contain basal cells (neuronal precursors) that allows epithelium to re-wire itself throughout life
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Where are olfactory receptor proteins located?
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In plasma membrane of receptor cells in the olfactory cilia
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Each olfactory neuron expresses...?
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One olfactory receptor protein
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Olfactory neuron axons expressing a single receptor type synapse on...?
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One glomerulus
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What is the pathway of olfactory signal transduction?
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Odorant binds GPCR on cilia --> G protein activated --> activates adenylate cyclase --> catalyzes synth of cAMP --> opens Ca channels --> influx of Ca opens Cl channels --> depolarizes cell
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How is the activation of the pathway controlled? (2)
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Ca binds to calmodulin --> complex binds Cl channel --> reduces affinity for cAMP
cAMP broken down by PDE |
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How is the cell adapted to sustained odorant stimulation?
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Ca extruded by the Na/Ca exchanger
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How are olfactory neurons expressing different receptor proteins arranged to maintain odorant specificity?
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Restricted to one of four zones in olfactory epithelium along turbinates
All the neurons of one type (expressing one type of receptor) synapse on a single glomerulus --> single mitral cell |
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How are glomeruli distributed to maintain specificity?
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Distribution of glomeruli for specific receptor types within olfactory bulb --> topographical map of each receptor type
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How is specificity of odor sensed?
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A discrete odor will stimulate all receptors --> spatial pattern of stimulated mitral cells --> brain interprets as a particular smell
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What are the 4 basic tastes?
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Sweet
Salty Sour Bitter |
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How does sensitivity for taste differ depending on the substance?
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Low sensitivity for flavors in normal foods (i.e. sweet, salty)
High sensitivity for potentially toxic substances |
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What are tastebuds?
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Cluster of neruosensory cells with small pore that is open to environment
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What are the 3 types of tastebuds and where are they located?
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1. Fungiform papillae (anterior tongue)
2. Foliate papillae (posterior tongue) 3. Circumvallate papillae (posterior tongue) |
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How is taste signal transduction similar to olfaction?
Different from olfaction? |
Similar: GPCR, rapid adaptation with continuous exposure
Different: multiple receptors on each neurosensory cell |
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What is the pathway of taste into the brain?
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Taste fibers from tastebuds --> CN 7,9,10 --> nucleus of solitary tract --> VPM thalamus
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What do branches of CN 7 sense? (2)
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1. Chorda Tympani = anterior 2/3 tongue
2. Greater superior petrosal branch = palate |
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What does CN 9 sense?
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Lingual branch = posterior 1/3 tongue
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What does CN 10 sense?
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Superior laryngeal branch = epiglottis, esophagus
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What is the structure/placement of the vomeronasal sensory organ?
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Cigar shaped with smooth muscular tube (pump?); lumen lined with chemosensitive neuroepithelium
Located in bony capsules at base of nasal septum |
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What is the VNO pathway in rodents?
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VNO sends axons --> accessory olfactory bulb --> projects to amygdala --> projects to hypothalamus
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What is the role of VNO in mammals?
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Receptor organ for pheromones
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What are pheromones?
What types of molecules do they include? |
Secreted substances that transmit information about gender, dominance, reproductive status
Low volatility molecules: steroids, prostaglandins, polypeptides, FAs |
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What is the Lee-Boot effect?
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Suppression of estrus can be reversed by prior removal of VNO in mice
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What is the Vandenbergh effect?
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Exposure of sexually immature female mouse to urine from a mature male speeds up uterine development and puberty
But effect is blocked if VNO removed |
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What is the Bruce effect?
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Fertilized mouse ova fails to implant if woman is exposed to strange male urine
Effect is blocked if VNO removed |
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What are 4 findings of cloned VNO pheromone receptors in mice?
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1. Distinct from sensory neurons in olfactory system
2. Different in males and females 3. Homologues demonstrated in humans, but mostly pseudogenes 4. Human males and females have differential hypothalamus activation patterns in response to estrogen or androgen |
