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54 Cards in this Set
- Front
- Back
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What is pharmacomechanical coupling?
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Couples changes in extracellular concentrations of membrane receptor agonists to changes in contractile activity of smooth muscle cells
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What is agonist affinity?
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AGONIST AFFINITY= COFACTOR AFFINITY
Affinity of receptor for agonist |
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What is receptor density?
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RECEPTOR DENSITY= ENZYME CONCENTRATION
more receptors --> more signal transduction |
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What is receptor gain?
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RECEPTOR GAIN= CATALYTIC ACTIVITY
Efficiency of receptor |
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What is the characteristic function of G-proteins?
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Bind & hydrolyze GTP
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When is the alpha subunit active?
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When bound to GTP
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Most important step to regulate in G-protein activation is?
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Control rate of GTP hydrolysis
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What happens to Gs receptors in presence of cholera toxin?
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Cholera toxin turns on Gs receptors in gut & increased water permeability --> severe dehydration
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What is the action of Gs coupling receptors?
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Activate adenylate cyclase
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What is the intracellular response of Gi coupling?
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Inhibit adenylate cyclase
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How does pertussis toxin act on Gi coupling?
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Gi is inhibited by pertussis toxin
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What is the intracellular response of Gq coupling?
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Activates Phospholipase C (PLC) from PIP2
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Activation of PLC releases which 2 molecules?
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1. DAG
2. IP3 |
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What is the function of DAG?
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Activate Protein Kinase C --> phosphorylates proteins
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What is the function of IP3?
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Sitmulates sarcoplasmic reticulum to release Ca2+ --> muscle contraction
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What are small G proteins?
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Small monomers involved in diverse signaling pathways
RAS superfamily: Ras, Rho, Arf, Rab, Ran Important for growth & proliferation |
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What are RGS proteins?
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proteins that accelerate GTPase activity of alpha subunits --> accelerate activation cycle
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Nernst equation is a relationship between which 2 factors?
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Chemical & electrical gradients
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What does the Goldman equation describe?
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Takes into account all of the molecules that are permeable to the membrane in order to determine the equilibrium potential
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What is the main voltage-sensitive Ca channel?
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L-type
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What is a common target for Ca antagonists?
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L-type
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Where are voltage-senstive channels typically found?
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Excitable cells-- muscle cells & neurons
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What types channels allow Ca influx to activate a cell? (3)
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1. L-type (& other voltage senstive)
2. Ligand gated 3. Stretch/leak |
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How do Ca stretch/leak channels operate?
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Mediate steady basal Ca influx proportional to the extent of stretch
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K efflux has what effect on the cell?
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Hyperpolarizes membrane potential & "quiets" the cell
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What types of K+ efflux channels are there (4)
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1. Voltage sensitive
2. ATP-sensitive 3. Ca sensitive 4. Inward rectifier |
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How do voltage-sensitive K channels effect cell?
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K efflux is activated by depolarization --> allows hyperpolarization to return to RMP
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How do K+ ATP-sensitive channels work/
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Low ATP in cell allows K+ to exit cell & hyperpolarize membrane to RMP
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How do K Ca sensitive channels work/
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Activated by high Ca --> K exits cell --> hyperpolarizes membrane
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What is the role of Cl channels?
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Cell volume regulation
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Direction of Cl movement is dependent upon?
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Membrane potential & Cl gradient
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Where is the IP3 receptor located?
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Sarcoplasmic reticulum on Ca channel
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Why is IP3 receptor important?
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Target for phosphorylation which regulates Ca flow into/ out of SR
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Where is the P2X receptor located?
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Plasma membrane of nerve & smooth muscle cells
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How is P2X receptor activated?
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Extracellular ATP
(P=purine & ATP= a purine) |
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Function of P2X receptor on plasma membrane?
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Carries Ca into cell --> promote cell activation
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How is tyrosine kinase receptor activated?
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Binding of ligand to each part of the receptors pulls them together to form a dimer
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Once the dimer of tyrosine kinase receptor is formed, what happens next?
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Autophosphorylates tyrosine residues
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Phosphorylated (active) tyrosine kinase then does what?
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Phosphorylation regulates:
1. Metabolic enzymes--> metabolic pathways 2. Transcripiton factors --> gene activity |
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2 examples of agonists for tyrosine kinase receptors?
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1. Insulin
2. Growth factor |
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Natriuretic peptide receptors activate which enzyme?
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Guanylate cyclase
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What does guanylate cyclase do?
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Converts GTP --> cGMP
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What does cGMP activate?
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Protein kinase G --> leads to phosphorylation
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2 natriuretic peptide receptor agonists?
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1. Atrial natriuretic peptide (enhances Na excretion)
2. Brain natriuretic peptide (regulates fluid balance) |
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What is sequestration?
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Internalization of receptors to inactive them--> RAPID PROCESS
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3 types of receptor inactivation?
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1. Sequestration
2. Desensitization 3. Down-regulation |
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What happens when a receptor is down regulated?
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Continuous activation inhibits new receptor synthesis (gene regulation) &/or stimulates receptor degredation & turnover
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What occurs in receptor densensitazation?
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Receptor phosphorylation slows signal transduction(specific or non-specific kinases)
Phosphatases can reverse this process |
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4 important classes of smooth muscle receptor agonists?
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1. Amines
2. Amino acids 3. Peptides 4. Purines |
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Examples of amine agonists? (4)
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1. Catecholamines
2. Ach 3. Histamine 4. Serotonin |
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Examples of amino acid agonists? (3)
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1. Gly
2. Glu 3. GABA |
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Examples of peptide agonists? (7)
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1. Angiotensin
2. Calcitonin gene related peptide 3. Endothelin 4. Natriuretic peptides 5. Substance P 6. Vasoactive intestinal polypeptide 7. Vasopressin |
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How are many peptide agonists released?
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As cotransmitters from perivascular nerves
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Examples of purine agonists? (2)
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1. ATP
2. Adenosine |
