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77 Cards in this Set
- Front
- Back
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What are the five types of chemical senses?
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1. Olfaction
2. GUstation 3. Visceral chemosensation 4. CO2 and O2 detection 5. Pheromone detection |
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What is the relationship between papillae and taste buds?
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Many taste buds are packed together to form taste papillae
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What are taste buds made of?
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Taste receptor cells
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Where are foliate, vallate, and fugiform papillae?
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Vallate are at the back of the tongue; foliate are at the back sides of the tongue; fugiform are at the front of the tongue
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What types of ions activate salt channes?
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Na+
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What types of ions activate sour channels?
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H+ (acidic)
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Describe the nerve path stimulated by the entrance of ions in salt and sour cells
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Ion flow depolarizes the sensory cell, because membrane depolarization leads to the entrance of Ca2+ leading to release of transmitter onto the gustatory fibers, which project to the gustatory ganglia, and then to the brain.
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Which is a PDK2 channel, salt or sour?
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Sour
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What type of taste receptors uses GPCRs?
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Bitter, sweet, and umami
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How do bitter, sweet, and umami tastes work?
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Bind to GPCRs, which activate Phosphlipase C, whcih converts PIP2 to IP3(the second messegner), which release Ca2+ stores, which lead to the influx of Na2+, which leads to the influx of Ca2+ (because it'svolotage-gated), which leads to the release of neurotransmitter
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What are the two group sof GPCRs?
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T1Rs and T2Rs, which are both expressed in taste cells and specifically present in taste cells
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Do taste cells express T1Rs and T2Rs?
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o, many express either or; some express neither; none express both
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How many T1Rs are there?
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#1-3
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How many T2Rs are there?
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#1-40
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How did they test the hypothesis that one class of GPCRs are for bitter tastes and others are for sweet tastes?
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Insert candidate taste reeptors into non-neurla cells that already have G proteins and second messenger systems. Present cells with taste receptor ligands and measure Ca2+ increase; for ex: when t2R5 was inserted, Ca2+ increased when CYX, which tastes bitter was presented, which suggests T2R5 is a cycloheximide receptor
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What are T2R receptors for?
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Bitter tastes
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What evidence suggested that T2R receptors are for bitter tastes?
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T2R5 responded to CYX; T2R10 responded to strychnine; T2R39 responded to phenylthiourea (PTU); T2R44 responded to detanonium; all of these taste receptor ligands are bitter
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What are T1R receptors for?
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Sweet and umami tastes
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What did the following respond to:
T1R1 T1R2 T1R3 |
Nothing
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What T1Rs responded to sweet?
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T1R2 + T1R3
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Do taste cells express T1Rs and T2Rs?
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o, many express either or; some express neither; none express both
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What T1Rs responded to umami?
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T1R1 + T1R3
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How many T1Rs are there?
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#1-3
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What are 3 components of "knockout" experiments?
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1. Homologous recombination
2. Embryonic stem cells 3. Germ-line chimerism |
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How many T2Rs are there?
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#1-40
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How does homologous recombination work?
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Targeting vector contains a mutated version of hte gene to be "knocked out;" insert into cell; in a small fraction of cases, vector will recombine with the native gene homolgously, replacing the active gene with the inactive gene; Capecchi and Smithies devised methods to select and detect the rare homologous recomibnatns
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How did they test the hypothesis that one class of GPCRs are for bitter tastes and others are for sweet tastes?
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Insert candidate taste reeptors into non-neurla cells that already have G proteins and second messenger systems. Present cells with taste receptor ligands and measure Ca2+ increase; for ex: when t2R5 was inserted, Ca2+ increased when CYX, which tastes bitter was presented, which suggests T2R5 is a cycloheximide receptor
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What did Capecchi and Smithies do?
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Devised methods to select and detect the rare homologous recombinants of homologous recombination
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What are T2R receptors for?
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Bitter tastes
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What are two properties of embryonic stem cells?
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1. They can divide to form more stem cell s(self-renewal)
2. They can differentiate into specialized cells |
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What evidence suggested that T2R receptors are for bitter tastes?
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T2R5 responded to CYX; T2R10 responded to strychnine; T2R39 responded to phenylthiourea (PTU); T2R44 responded to detanonium; all of these taste receptor ligands are bitter
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What are the cells inside of the blastocyst called?
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Inner cell mass (pluripotent cells)
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What are T1R receptors for?
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Sweet and umami tastes
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What did the following respond to:
T1R1 T1R2 T1R3 |
Nothing
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What T1Rs responded to sweet?
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T1R2 + T1R3
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What T1Rs responded to umami?
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T1R1 + T1R3
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What are 3 components of "knockout" experiments?
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1. Homologous recombination
2. Embryonic stem cells 3. Germ-line chimerism |
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How does homologous recombination work?
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Targeting vector contains a mutated version of hte gene to be "knocked out;" insert into cell; in a small fraction of cases, vector will recombine with the native gene homolgously, replacing the active gene with the inactive gene; Capecchi and Smithies devised methods to select and detect the rare homologous recomibnatns
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What did Capecchi and Smithies do?
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Devised methods to select and detect the rare homologous recombinants of homologous recombination
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What are two properties of embryonic stem cells?
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1. They can divide to form more stem cell s(self-renewal)
2. They can differentiate into specialized cells |
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What are the cells inside of the blastocyst called?
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Inner cell mass (pluripotent cells)
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Which cells are isolated for stem cell research?
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Those form inside the blastocyst
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Describe germ-line chimerism.
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Targeted ES cells are injeted into blastocysts where they mix and form a mosaic with the cells of the original inner cell mass; the injected balastocysts are implanted into a surrogate mother where they develop; mosaic mice are born; the mosaic mice mate with normal mice to produce both gene targeted and normal offspring; gene targeted mice are called "knockout mice"
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Describe the behavioral analysis of TR knockout mice.
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"Lick-ometer;' in T1R1 or T1R3 mutants, there was no response to umami tastses; responses to other tastes were fine; response to umami was also fine in T1R2 knockouts
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What did the lick-ometer prove?
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That T1Rs are not only sufficient for umami detection, they are necessary
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What type of mice have genes removed?
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Knock-out mice
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What type of mice have genes replaced?
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Knock-in mice
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What type of mice have genes added?
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Transgenic mice
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What is it called when the mRNA is copied into DNA?
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cDNA
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What do the regulatory sequences tell when it precedes DNA?
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Where and when a gene is expressed
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What happens if the regulatory sequence is AChR and the subsequent cDNA is AChR?
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Extra AChR in muscle
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What happens in AChR and the subsequent cDNA is Opsin?
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Opsin in muscle
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What happens if Opsin is the regulatory sequence and the subsequent cDNA is AChR?
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ACHr in photoreceptors
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How are transgenic mice formed?
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Foreign DNA is injected into one of the pronuclei (in the fertilized mouse egg); transfer injected eggs to foster mother; about 10 to 30% f the offspring contain injected foreign DNA, which is present in equal amounts in all tissue; mice expressing foreign DNA are bred to continue DNA in germ line
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Give 3 examples of transgenic mice sequences.
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- Ubiquitous as regulator + GFP as subsequent sequence makes entire mouse glow
- Cortex as regulator + GFP as subsequent sequences makes cortex glow - Neurons as regulator + XFP as subsequent sequence makes neurons glow |
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What are 3 interspecies difference between mice and humans regarding taste?
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1. Humans taste aspartame (Nutrasweet) but mice don't
2. Human taste several compounds as bitter that mice don't 3. Mice taste many amino acids, but humans primarily taste glutamate |
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What is an interspecies difference between cats and humans?
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Cats are insensitive to sweet tastes
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Give an example of the way interspecies differences were used to test the effect of human T1R2 cells.
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Mouse T1R2 was used as the regulatory sequence and human T1R2 cDNA followed, rendering mice sensitive to asartame
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What happened when the regulatory sequence was mouse T2R19 (bitter cells) and the cDNA was human T2R16.
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Human T2R16 is a GP receptor in "bitter' cells, so mice did not like it
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What happened when the regulatory sequence was mouse T1R2 (sweet cells) and the cDNA was human T2R16?
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The sweet receptor makes them like it
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What did the test show, in which bitter receptors were placed in a bitter cell, versus bitter receptor being placed in a sweet cell.
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It showed that the receptor only accept the chemical; the cell (not the chemical) determined what was rendered attractive or aversive.
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What do taste receptors mediate?
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Sensation of taste
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What does the taste you sense depend on?
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The neuron in which the receptor is expressed (as a result of the type of cell)
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What are 7 senses humans have?
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1. Vision
2. Audition 3. Gustation 4. Olfaction 5. Somatosensory (touch, thermoception, nocioception (pain)) 6. Balance (vestibular) 7. Proprioception |
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What is nocioception?
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Pain
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What is the vestibular sense?
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Balance
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What is proprioception?
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Movement of the body/body position
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What is a sense that birds have?
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Magnetoception
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What is a sense that bats have?
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Sonar
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What is a sense that some fish have?
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Electroception
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What is a sense that mice have?
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Pheromone reception
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What is a sense that snakes have?
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INfrared sense
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What senses depend on GPCRs?
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1. Vision (4 receptors)
2. Olfaction (300-1000 receptors) 3. Gustation: sweet, bitter, umami (40 receptors) |
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What sense are gated channels?
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1. Gustation: salt, sour
2. Hearing 3. Somatosensation 4. Thermoreception 5. Vestibular sense 6. Ptroprioception |
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WHat are the 4 attributes of a sensation?
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1. Modality
2. Locaiton 3. Intensity 4. Time course |
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Describe the 3 types of cells involved in modality?
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1. Meissner's corpuscle for light touch
2. Merkel cells for pressure 3. Pacinian corpuscles for vibration |
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What 3 phenomenons cause us not to experience the world as it really is?
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1. Selective attention (magnification factor/homunculus)
2. Contrast detection (Thunberg's thermla grill causes the illusion of painful heat from alternating warm and cool bars) 3. Adaptation |
