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24 Cards in this Set
- Front
- Back
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What is a primary messenger?
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Signal that functions to disseminate information to cells
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What are the various types of receptors?
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Ligand-gated ion channels
G-protein coupled Enzyme Receptors Nuclear Receptors |
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What is a transducer?
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Usually a transmembrane protein that is activated by the receptro and relays the signal of the primary messenger
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What is an effector
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Serves to amplicfy the signal given by the transducer;
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What is a second messenger?
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Generated by an activated effector; a key component of the amplification process
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what type of receptors are nicotinic receptors?
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They are acetylcholine ion channel receptors. Because they are channels and not enzymes they act rapidly
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How many Ach molecules does it require to activate Nn or Nm receptors?
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Both require two Ach molecules
Nn - being neuronal made of heteropentamer of 2 alphas and 3 betas or a homopentamer of 5 alpha subunits Nm being Neuromuscular Junction receptors of a pentamer being 2 alpha, 1 beta, 1 gamma, and 1 delta |
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How many known muscarinic receptors are there and how many are clinically significant and what type of receptors are they?
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There are 5 known with 3 clinically significant
THey are G-protein coupled receptors that bind Ach. Because they are G-protein their responses are slower |
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The G-protein coupled receptor is made of?
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trimeric proteinalpha, beta, and gama subunits
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What are the characteristics of an M1 receptor?
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It is a Gq coupled receptor. Gq referring to the alpha subunit isoform. The effector is PLC which causs and increase in intracellular Ca2+. Along with PLC activation the product DAG also causes PKC activation.
M1 is involved in the depolarization of ANS and CNS, and the production of Acid |
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What are the characteristics of M2 receptors?
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They are coupled to Gi proteins causing a down regulation of Adenylate cyclase inhibiting intracellular cAMP. Ultimately this decreases intracellular Ca2+ decreasing cardiac muscle contractility. It may also be coupled to a potassium ion channel leading to hyperpolarization inhibiting the heart depolarization. Ach also causes NO production to relax muscls
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What are the characteristics of M3 receptors?
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Gq coupled like M1. SLUD effects.
Salivation, Lacrimation, Urination, Defecation Generation of IP3 and increased Ca2+ causing Bronchial, sweat, and salivary secretions Acts on endothelium where it increases NO causing relaxation of vasculature. |
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Where is the alpha 2 receptor located at the postsynaptic neuron junction?
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On the presynaptic membrane as a feedback inhibitor of NE release
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Adrenergic receptors are what type of receptors?
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G protein coupled
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What are the characteristics of the alpha 1 receptor?
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Alpha 1a, 1b, and 1d are subtypes.
It is a Gq protein that similar to other Gqs (M1 and M3) will activate PLC causing IP3 and DAG production ultimately leading to an increased in Ca2+ |
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Characterize the Alpha 2 receptor.
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Subtypes Alpha2a, Alpha2b, alpha2c.
A presynaptic Gi/o inhibitor receptor. Utilizes NE. It is aka autoreceptor (transformers... more than meets the eye) Inhibits AC which decreases cAMP levels. |
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What effects does binding the Alpha 2 receptor have?
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Decreases insulin secretion, causes aggregation of platelets, causes presynaptic inhibition of NE, and relaxes inestinal smooth muscle. It is also coupled to a potassium channel which causes hyperpolarization
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All the Beta receptors are what type?
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Gs protein receptors. meaning that they activate Adenylate Cyclase and increase cAMP levels.
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Characterize the Beta 1 receptor
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Positive ionotrophic and chronotropic effects on the heart; speeds conduction across the AV node.
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What regulates heart contractility?
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The balance between Gs and Gi stimulation. Both together have effects on Ca2+ levels leading to modification of the contractile responses in the heart. Beta 1 vs M2
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Characterize the Beta 2 receptors.
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located on vasculature. Increases blood flow to skeletal muscles.causes a relaxation of vascular, bronchial, gastrointestinal and genitourinary smooth muscle, stimulate the uptake of potassium into skeletal muscles, stimulates glycogenolysis and gluconeogenesis in the liver
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Explain how it is that Beta 1 can cause cardiac contraction while Beta 2 causes smooth muscle relaxation both being Gs protein receptors?
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Gs activation leads to increase AC and increased cAMP. Increase in cAMP in smooth muscle ctivates PKA causing phosphorylation of MLCK. Phosphorylated MLCK is inactive preventing binding to Ca2+ thereby preventing contraction.
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What is the paradoxical effects on vaculature with regards to beta and alpha receptors?
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Alpha 1 and Beta receptors are both located on the vasculature. At low concentrations Beta 2 receptors have a higher affinity to Epi causing a vasodilation, but as concentrations get larger the increase in alpha 1 stimulation overrides the beta 2 stimulation causing vasoconstriction
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Characterize the Beta 3 receptors
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Adipose tissue: lipolysis important source of energy from fat metabolism.
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