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9 Cards in this Set
- Front
- Back
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Olfactory receptors |
G protein coupled receptors Located on the olfactory cilia of the olfactory receptor cells |
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Mucus |
Contains immunoglobulin and cytochrome p450 enzymes to protect neurons Odorants must penetrate mucus to gain access to olfactory receptors |
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Sense of smell |
Starting conditions - olfactory receptors localised on olfactory knob and cilia - Olfactory neuron- specific trimeric G protein is associated with with Olfactory receptors - G Protein has GDP bound Initial steps - Odorant molecule bi do to Olfactory receptors - G Protein exchanges GDP for GTP - G Protein is now activated Amplification of signals - G protein alpha subunit binds to and active Adenyylate cyclase iii - Adenylate Cyclase iii coverts ATP to CYCLICAL - cAMP Binds to and activates a cyclic nucleotide gated na+/ca2+ - na+/ca2+ enter the cell causing Depolarisation of the membrane potential Final steps - Ca2+ binds to and activates a Ca2+ gated cl- channel - cl- exits the cell causing further Depolarisation of the membrane potential - passive conduction of Depolarisation to axon hillock -》 olfactory neurons fire action potential Adaptation - Ca2+/ Calmodulin (CaM) binds to and decreases sensitivity of AMP- GATED Channels - Extrusion of Ca2+ by Na+/Ca2+ exchange proteins - Ca2+ modulates phospodiesterase and increases co version of cAMP 》 AMP |
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Amplification of the olfactory signal |
G protein alpha subunit unit indicates and activates Adenylate Cyclase III Adenylate cyclase III converts ATP to cyclic AMP |
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Initial steps of olfactory pathway |
Starting conditions - olfactory receptors localised on olfactory knob and cilia - Olfactory neuron- specific trimeric G protein is associated with with Olfactory receptors - G Protein has GDP boundInitial steps - Odorant molecule bi do to Olfactory receptors - G Protein exchanges GDP for GTP - G Protein is now activated Amplification of signals - G protein alpha subunit binds to and active Adenyylate cyclase iii - Adenylate Cyclase iii coverts ATP to CYCLICAL- cAMP Binds to and activates a cyclic nucleotide gated na+/ca2+ - na+/ca2+ enter the cell causing Depolarisation of the membrane potential Final steps - Ca2+ binds to and activates a Ca2+ gated cl- channel - cl- exits the cell causing further Depolarisation of the membrane potential - passive conduction of Depolarisation to axon hillock -》 olfactory neurons fire action potential Adaptation - Ca2+/ Calmodulin (CaM) binds to and decreases sensitivity of AMP- GATED Channels - Extrusion of Ca2+ by Na+/Ca2+ exchange proteins - Ca2+ modulates phospodiesterase and increases co version of cAMP 》 AMP |
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Number of olfactory receptors |
950 human olfactory response genes 400 functional Remainder pseudogones |
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5 fundamental tastes |
Salt - Na+ Sour - Acidic substances , H+ Sweet - Sugars, D-amino acids, artificial sweetners Umami - L amino acids (especially. L-glutamate in humans) Bitter - a wide range of bitter compounds Fats???? Ca2+, CO2, H20 |
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50-100 elongate taste cells 3 classes |
50-100 elongated taste cells 3 classes Renewing population basal cells Type 1 - Glial like cells, - Express epithelial Na+ channel, may be involved in transduction of salt taste Type 2 - Express the receptors responsible for sweet, umami and bitter taste - contact Afferent nerves, but don't form regular synapses with Vesicular NT release Type 3 - Express H+ sensitive channels - Transduce Sour taste - Form regular synapses with Vesicular release of NTs - ATP,noradrenaline, Seretonin |
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Sour taste transduction |
Type iii cell Initiated by proton enter through an apically located proton selective ion channels Weak acids may also activate sour cells - acidity cytosol Leads to closure of k+ channels, membrane Depolarisation Voltage gated ca2+ channels open -》 Vesicular NT release |
