Term
| examples of adaption to avoid desensitization |
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Definition
alternating drug delivery to every other day
pulsatile release of hormones like how the hypothalmus does - it releases hormones in pulses very 20 mins
these are self regulatory processes |
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Term
| why would a cell have spare receptors |
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Definition
to allow for an alternate signal transduction. one signal will be carried out at low agonist conc and a diff will be carried out at high. like insulin: low conc stim glucose uptake, high works as a growth factor
also, it can make a target cell more sensitive to the hormone |
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Term
| what kind of agonists act on PM surface receptors? |
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Definition
water soluble agonists and proteins
small lipid solubles like prostalandins |
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Term
what kind of agonists act on cytosol and nuclear receptors?
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Definition
| lipid soluble molecules, steroids, thyroxin, retinoids |
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Term
| what are the differences in receptor affinities for agonists for hormone receptors and neurotrasmitter receptors? |
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Definition
hormone receptors usually have a very high affinity for their agonists that that they can take place in long activations of their pathways.
neurotransmitters require more agonist and therefore have a lower affinity. this is necessary to maintain quick on/off activiation capabilities |
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Term
what happens when you lower receptor saturation?
raise saturation? |
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Definition
the receptors become more sensitive to any agonist present and the result is upregulation of activity. this is also true if there is competitive inhibition since the true saturation of meaningful agonist is low
raise the saturation and tolerance begins to occur. down-regulation of activity takes place |
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Term
| what pathology can happen to the nicotinic ach receptor? |
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Definition
| curare, a snake toxin and bind to it and block acetylecholine binding. this wont allow the ion channel to open and since it is is a postganglion neuron at the neuromuscular junctions, paralysis can insue |
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Term
| describe a cAMP-using pathway |
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Definition
GTP bound alpha sub activates adenyl cyclase, AC converts ATP to cAMP, cAMP activates PKA, which can phosphorylate or activate any number of kinases
i.e. CREB -> CREB-P which when activated can go to the nucleus and stimulate transcription
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Term
| what can cholera toxin do |
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Definition
| cause ADP ribosylation which abolishes GTPase activity leaving the G-protein constitutively on |
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Term
| common large g-protein second messengers |
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Definition
cyclic nucleotides, cAMP, cGMP
intracellular Ca2+
membrane phospholipid breaddown products like IP3 and DAG, arachidonic acid, and aicosanoids |
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Term
| calcium as a second messenger |
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Definition
cannot be created or destroyed, just moved around.
at a higher conc outside the cell
it can work with calmodulin (a Ca binding protein like toponin C). calmodulin may be present on the surface of an enzyme and Ca binding to it may activate, or it may be free floating and when they bind together they make a complete agonist. Calmoudin has 4 binding sites |
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Term
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Definition
a phospholipase (such as phospholipase C) that has been activated by the alpha subunit of a large G protein can cleave PIP2 which is connected to the PM. DAG will stay membrane bound. DAG is then capable of activating PKC, which phosphorylates and alters many others
meanwhile, IP3 binds to receptors on ER and releases CA2+ stores. Ca2+ can increase the activity of PKC. |
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Term
| uses of arachadonic acid as a second messenger |
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Definition
a phospholipid tail which can be cleaved by phospholipase A2. it can now serve as a signalling molecule, or a parent molecule for other future messengers, or diffuse out of the cell and have profound paracrine effects on neighboring cells
it can also be metabolized into compounds called eicosanoids. |
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Term
| what is something that the beta-gamma G-protein subunits can activate? |
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Definition
K+ ion channels in the heart.
and Ach receptor in the vagus nerve |
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Term
| what does aspirin inhibit? |
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Definition
| both isoforms of COX (1 and 2) |
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