b455 chemosenses

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b455 chemosenses
2013-03-04 11:15:41

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  1. 1. What are receptor organs for taste?
    2. What is mechanism for these receptor organs?
    3. Types of receptors? (3) What is different about them? Do they detect different tastes? If not, why are they different?
    4. Why does each taste bud only have receptors for one taste?
    • 1. Taste buds on tongue
    • 2. Taste chemicals enter bud through pore and have access to cells w/ receptors on them. When they reach generator potential, will release NT that projects from spinal cord to thalamus.

    • 3. Fungiform, foliate, and circumvallate - different morphologies, not for taste, but for different ways of accessing chemicals freed in foods in mouth.
    • 4. It doesn't! Each papillae has all different classes of taste buds in different proportions?
  2. 1. What kind of receptors detect sour? What is specifically detected?

    2. What kind detect salty? What is the ligand? (3) When ligand bind, what happens to channel? What does most salt sensation come from?

    3. What kind of receptor do all of the other tastes use? What messenger does it use? What are teh two families? How does it determine what taste will be detected?
    1. Ion channels detecting H+. H+ ions block K+ causing direct depolarization.

    - Graded and will be proportional to amount of sour: more H+ --> more blocking of K+ ions --> increased depolarization

    2. ion channels (Na, K, Ca). Channel depolarizes. Na+

    3. Metabotropic - G-linked protein. T1R and T2R. Combo of different receptors and homo/heterodimers will determine how tastes are detected
  3. Which taste receptor has graded effect?
  4. What are the receptors for:
    1. Sweet
    2. Bitter (how many different types of bitter receptor? Why do we have this number? What are we limited by?)
    3. Umami (2)
    1. T1R, T1R2, T1R3 -  different genes combine in heterodimer to make one receptor; T1R2 mutated in cats

    2. All T2R - 30 different types to have large range of detecting bitter to detect poisons. but we can't discriminate between bitter tastes

    3. (1) Metabotropic glutamate receptor - MSG causes excitoxicity of these receptors in brain - remember, other glutamate receptor are ionotropic (NMDA, AMPA) overstimulates tongue and brain - migraines.

    3. Heterodimer: T1R1 and T1R3 - broader range of sensitivities - can respond to most amino acisd.

  5. What type of processing does taste use?

    Draw organization of taste (4)
    • Parallel (labeled lines) from tongue to cortex - even kept separate in cortex!
    • - When you taste flavor, population of receptors are activated - combo of sweet and bitter will taste different (population coding).

    Tongue ---< Brain stem ---< Thalamus ---< cortex (somatosensory aka gustatory)
  6. 1. What system detects smells?
    2. Describe pathway of smell in main olfactory system. How is this different from other sense?
    3. What cells are found in main olfactory system? 3
    • 1. Main olfactory
    • 2. Olfactory epithelium --<olfactory bulb ---< cortex (NO PROJECTION THROUGH THALAMUS)
    • 3. Receptor, supporting, basal
  7. Describe receptors for main olfactory system and accessory olfactory system

    Which uses labeled lines?
    Main: Each receptor cell expresses one single olfactory receptor (G-protein linked); four subfamilies (Golf). Labeled lines

    Accessory: V1, V2, G-protein linked, no labeled lines since porjections are more about comparing inputs rather than discriminating precise info.
  8. 1. Which olfactory system is used to identify specific females? A female?

    2. How many functional genes do humans have for olfactory receptors? How do we preserve info about smells and smell more smells than we have genes? (1-2, 1)
    1. Main; accessory

    2.~350. Using population/pattern coding (1) single receptor cell for each receptor - each can detect a range of odor cues and respond differently (2) Odorants bind to receptors with different efficacies - different generator potentials produced).

    And labeled lines.
  9. What is projection pathway of main olfactory system? 4 final pathways
    • Olfactory epithelium on receptors ---< olfactory bulb¬† ----<
    • 1. Primary olfactory (prepyriform) cortex - sensation of smell
    • 2. Entorhinal cortex - learning & memory by projecting to hippocampus
    • 3. Amygdala (emotion)
    • 4. Hypothalamus - hormones and motivated behavior
  10. 1. What is stereoolfaction?
    2. How can rats determine stereo-olfaction? (2) Probably by comparing what?
    3. Experiment?
    4. What part of main olfactory system can detect location - what types of location exactly? What can't? Why and why not?
    • 1. Location of source of scent
    • 2. By comparing timing and intensity of stimulus in each nares (onset/offset of stimulus and firing rate)
    • 3. Rats sniffed air and if smell came from left, that's where water is and vice versa. Could accurately detect 80% of time - but when one nostril was stitched touch - could only detect 50% of the time - basically based on chance.
    • 4. Prepyriform cortex (NOT MAIN OLFACTORY BULB) because prepyriform is bilateral and MOB is unilateral.

    Prepyriform cortex can detect locations coming from unilateral (detecting from same side of animal's body), bilateral (from two sites) and contralateral (across).
  11. 1. What are three characteristics of accessory olfactory system?
    1.5 - what type of organ is important for accessory olfactory system? Who doesn't have it?
    2. What types of cells does it have? (3)
    3. What is it not designed to detect?
    4. What part of using accessory olfactory system is behavioral? example?
    • 1. Specialized, few receptors, part of communication system
    • 1.5. Vomernasal organ - humans (if we do, receptors have been mutated) and birds.
    • 2. Like MOS, AOS has receptor, supporting and basal cells
    • 3. Airborne chemicals
    • 4. B/c of above, allowing access of chemicals into is a behaviorally active process. Cats scrunching their noses.
  12. 1. What does vomernasal organ respond to?
    2. Define the substance VN organ responds to from above
    3. What is the response? (2)
    4. Are these signals usually species-specific or not?
    5. What can signals lead to?
    6. How does AOS differ from MOS in terms of receptors?
    • 1. Pheromones
    • 2. Pheromones - chemical communication signals that one organism produces for the sole purpose of eliciting a response in the receiver who detects hormone.
    • 3. Behavioral or hormonal (usually hormonal)
    • 4. Yes, species-specific
    • 5. Signals can lead to aggression, sexual, changes in arousal.
    • 6. AOS has way fewer receptors - not a generalist system like MOS
  13. What do MOS and AOS have in common? 3

    Differ? 7
    1. Start with olfactory epithelium, similar structures, G-protein-linked receptors,

    • 2.
    • - Olfactory epithelium located in different anatomical locations
    • - MOS has more receptors, can smell, generalist system
    • - MOS has emphasized access to cortex while AOS has emphasized access to amygdala and hypothalamus
    • - MOS has labeled lines, AOS doesn't
    • - Some say that AOS doesn't exist in humans bc genes aren't expressed due to mutations
    • - MOS distinguishes which female, while AOS distinguishes male vs. female
  14. What are receptors for AOS vs. MOS?
    AOS - V1 and V2 - info from these receptors is kept separated at this bulb.

    MOS - Golf (4 subfamilies)

    These receptors are evolutionarily distant from each other!
  15. 1. Preti et al study?
    2. Women and synced menstrual periods? 2
    3. Does Martha McClintock think we have vomernasal organs?
    1. Extracted pheromones from males decrease latency of LH surge triggering earlier ovulation

    2. Depends on if donor is in follicular phase (shortens time to ovulation) or post-menstruation (lengthens time to ovulation for receiver)

    3. Yes - might be in MOB and info is shared with amygdala and hypothalamus.