Title: BV4 / Modul 2 / Lukt/Smak

Q: HOw are the tastebuds distributed on the tongue?
A: The tastebuds are distributed over the tongue in some quite arranged manners

Q: Which 3 types of papillae are there?
A: - Circumvallate
- Foliate
- Fungiform

Q: Which reception fo circumvallate have?
A: Bitter

Q: Which reception does foliate have?
A: Sour

Q: Which reception does fungiform have?
A: Sweet and salty

Q: How bit a part of the tastebuds does circumvallate represent?
A: 48%

Q: How bit a part of the tastebuds does foliate represent?
A: 28%

Q: How bit a part of the tastebuds does fungiform represent?
A: 24%

Q: What are circumvallate innervated by?
A: n. glossopharyngeus

Q: What are foliate innervated by?
A: n. Glossopharyngeus

Q: What are fungiform innervated by?
A: n. facialis

Q: What is the transduction mechanism of salt and acids?
A: Ion channels - Salt and acids are channels that are sensitive to ions

Q: What is the transduction mechanism for salt?
A: Amiloride-sensitive Na+ channel - Na+ goes in

Q: What is the transduction mechanism for acids?
A: H+-sensitive TRP channel (PKD variant) - H+ goes in

Q: What can be said about teh transduction mechanisms for salt and sour?
A: These mechanisms are very rapid

Q: What is the general transduction mechanism of sweet, amino acids (Umami) and bitter?
A: In contrast sweet, amino acids and bitter are GPCR and thus there is an intracellular cascade that makes the perception of these a bit slower than those for sour and salt

Q: Which receptors are involved in the perception of sweetness?
A: Sweet is involving T1R2 and T1R3 receptors coupled to g-proteins,  and it also involves PLC-beta2, inositol3-phosphate and TRPM5-channels

Q: Which receptors are involved in the perception of umami?
A: - In umami we have 2 T1R1-receptor coupled to T1R3, g-coupled proteins that are stimulating PLC and then the cascade will open the TRPM5 -channels

Q: Which receptors are involved in the perception of bitter?
A: For bitter its the T2R receptor, and we have the same intracellular cascade as in umami

Q: What do mutations in the TRPM-channels affect?
A: So mutations in the TRPM- channels affect bitter, sweet and umami in the same way

Q: What is the receptor difference between umami and bitter perception?
A: The difference with umami amino acids and bitter is the first receptor with which  this is propagated, this info will propagate even tho the intracellular cascade is the same

Q: What does the TRPM5 channel let throught?
A: Ca2+ ions

Q: Which models were discussed
A: - Labelled-line model
- Across-fibre models (2 types)

Q: How does the labelled-line model work?
A: We have a mixture of different cells where each of them convey a single taste information which propagates towards the CNS

Q: How does the across-fibre models work?
A: 1. If one cell could present different types of receptors and then this would be sent towards the brain
2. Another model in which every cell would have one information for 1 taste, but then that mixture will happen at the level of the neurons

Q: What was agreed about the different neural coding in the taste system?
A: It was agreed that none of the across-fiber models were responsible for that and that taste cells responde to a single-taste stimulus based on the receptor that they are expressing and that the underlying nerve fibers also transmit that specific repsonse

Q: What do taste cells respond to?
A: Taste cells respond to a single taste stimulus based on the receptor present in the cell
The nerve fibers transmit this specific respons to the brain

Q: What can be said about teh taste connections in the central nervous system?
A: There are a number of taste connections in the central nervous system and here we see that from the tongue we have projections towards the nucleus of the solitary tract then we reach the thalamus and then insular and frontal taste cortices

Q: To where do we have projections from the tongue about taste perception?
A: From the tongue we have projections towards the nucleus of the solitary tract, then we reach the thalamus and then insular and frontal taste cortices

Q: Why are there connections with the hypothalamus and the amygdala when it comes to food?
A: There are connections with the hypothalamus and the amygdala bc there there is a subcontious perception of the taste whether its a good or bad one - emotions are being conveyed here - the thalamus is also providing a distinction of different taste experiences

Q: What is the gustatory nucleus associated with?
A: The gustatory nucleus is associated with the sense of taste and has two sections, the rostral and lateral regions

Q: What is the VPM of the thalamus?
A: Ventral posteromedial nucleus

Q: Where is the gustatory cortex?
A: Postcentral gyrus

Q: WHat happens in the thalamus connected to taste?
A: Thalamus: distinction of different taste experiences

Q: WHat happens in the insula connected to taste?
A: Insula: provides a concious perception and discrimination of taste stimuli

Q: How is stimuli transmitted from tongue to CNS?
A: Taste buds (n. IX, X, XI) -> nucleus of solitary tract (gustatory nucleus(?)) -> VPM of thalamus (but also amygdala and hippocampus) -> Insular and frontal taste cortices

Q: What is the structure in the nasal cavity of the olfactory organ?
A: In the nasal cavity we have olfactory receptor cells that are in the mucosa, that is secreted by those bowman's glands, we also have a number of dividing stem cells bc the olfactory epithelium regenerates these cells in a regular manner

Q: To where do olfactory cells have projections?
A: The olfactory receptor cells have projections towards the olfactory bulb

Q: What are glomeruli?
A: Glomeruli are bundles of axons and dendrites

Q: What are periglomerular cells?
A: Periglomerular cells are involved in lateral inhibition

Q: What are mitral cells?
A: Mitral cells are the principal neurons on the olfactory bulb

Q: What are granule cells?
A: Granule cells are inhibitory interneurons

Q: To where do olfactory receptor cells project?
A: Those olfactory receptor cells project towards the glomerulus which is a big bundel of axons and dendrites - this is the first centre that capture the info

Q: What can mitral cells be called and what is their role?
A: The intermediate cells are called mitral cells and these are the ones that are the principal ones in the olfactory bulb

Q: What is the role of the granule cells?
A: Here in addition we have the granule cells which also are inhibitory interneuorns, so similar to the retina we have a numer of cells that will hepl making a refinement in the resolution in the perception of the odors

Q: Where are the receptors of olfactory receptor cells?
A: - The cell, the olfactory receptor cell, have the cilia present in the mucosa, this is where the receptors are located and not among the cellbodies of the cells

Q: How does the transduction mechanism work at cellular level?
A: The odorant molecules will activate the odorant receptor protein which is also G-coupled, but here instead we have a mechanism involving adenylyl cyclase -ATP -> cAMP which then will activate sodium and calcium channels and will cause a depolarisation of the membrane

Q: What are most odours composed of?
A: Most odours are composed of multiple odorant molecules

Q: What does each odor molecule activate?
A: Each odorand molecule activates several odorant receptors

Q: What does the fact that each odorant molecule activates several odorant receptors lead to?
A: This leads to a combinatorial code forming an "odorant pattern"
- This is why we can recognize 5000-1000+ different odours

Q: What does one olfactory receptor encode for?
A: One olfactory receptor cell encodes for one receptor

Q: What hepls us capture the complexity of teh different odours?
A: What hepls us capture the complexity of the different odors is how unspecific those odorant molecules are over those receptors - for instance if u take the ex. of #c, #c will bind to the receptor called 1 for 5, 7, 10 and 11, while the molecule E which is slightly differnet will also bind to number 8 and this will make a slighlt differnet perception over these odors

Q: What are most odors composed of?
A: So most odors are composed of multiple odorant molecules, each molecule activates several of those receptors, this causes a combination of code that we call th odorant pattern and this is why we can recognize 5000-10000 differnt odors

Q: How does infromation about smell reach the CNS?
A: In the central connects, a little bit similar to the taste we also have the involvmevent of the thalamus, hypothalamus as well as the amygdala, all of these connections are related to the olfactory bulb that then project for a more global perception - so we have the involvement of memory in the process which hepls u remeer that one odor is not good and another one is asscoiated with plesantness

Q: What else do we have involvement of in the process of smell perception coding?
A: We have the involvement of memory in the process which hepls u remeer that one odor is not good and another one is asscoiated with plesentness

Q: What happens concerning central smell connections in the orbitofrontal cortex?
A: Medveten diskriminering (trevlig vs obehaglig?

Q: What happens concerning central smell connections in the hypothalamus?
A: Minne

Q: What happens concerning central smell connections in the hippocampal formation?
A: Minnesåterkallelse

Q: Vad sker i entorhinal cortex?
A: Minneslagring