Block voltage gated Na+ channels so no action potential.
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The effect of local anaesthetics
Interact with the alpha-subunit and physically 'plug' transmembrane pore. Binds in the ionised (hydrophilic) form. Binding area is located in the inner end of channel
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What are the 3 subunits of voltage gated ion channels?
alpha, beta 1 and beta 2
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the alpha-subunit =
a single polypeptide. Contains extracellular domains. 4 transmembrane domains each comprising of 6 alpha-helical regions
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The beta1-subunit =
subunits flank alpha subunits - not linked
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The beta2-subunit =
linked covalently to alpha
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When voltage varies what happens in voltage gated ion channels?
voltage sensors change their orientation - this determines the configuration of the entire domain and controls opening/closing of a pore
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Most anaesthetics are....
weak bases
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What does the general structure of local anaesthetics consist of?
Aromatic group, ester or amide group and amine group
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Local anaesthetics: what does the basic side chain ensure?
That the molecules are ionised at physiological pH
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Local anaesthetics: What does the aromatic domain ensure?
Lipid solubility
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Local anaesthetics: How is the action limited?
By the hydrolysis of ester/amide bond and by lipid solubility
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Local anaesthetics: Where does ionisation take place?
Inside the axon
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Local anaesthetics block conduction in ...... .......... fibres more effectively
small diameter
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How do we restrict the site of action of local anaesthetics and prolong the action?
Coadminister with adrenaline
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How do we accelerate the speed of onset of local anaesthetics?
Use slightly alkaline solution - assist n absorption into nerve tissue
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What are the side effects of local anaesthetics? CNS, CV
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