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18 Cards in this Set
- Front
- Back
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the distinct mechanisms that cause ion channel dysfunction
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To understand how the malfunction in one or more of the basic properties of an ion channel in neurons or skeletal muscle fibers can explain pathologies of the neuromuscular system.
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To correlate, using a few better studied neurological disorders, the basic relationships between channel dysfunction, action potential alteration, synaptic transmission, and a given patient syndrome.
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To understand the inherent difficulties in extrapolating the behavior of an ion channel in an in vitrosystem to a nerve cell in the middle of a complex network of neurons.
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Ion Channel Diseases.
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A) Gene mutation: defective channel protein and/or accessory protein not properly expressed;
B) Autoimunediseases: |
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Thus, so far alterations in gating mechanismsare likely to cause disorders or diseases. These alterations canbe:
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Myotonia
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It is defined as a series of involuntary contractions of skeletal muscle following one or more voluntary contractions. This is a clear indication that repetitive action potentials (APs) are being automatically generated after a train of voluntaryAPs(hyperexcitability). Only Cland/or Na channels were so far been found involved in myotonia. Considering their seminal role in AP generation, it is surprising that K channels mutations have so far not been found in myotonia.
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Myotoniasrelated to Cl-channel mutations. Human dominant myotoniacongenita(DMC, Thomsen’s disease), recessive myotoniacongenita. Low membrane gCl(CLC 1 channels).
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Why can’t the Clchannel deliver the Cl-current necessary to stabilize the resting membrane potential?
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Channelopaties affect the permeation of the channel not the gating.
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Myotoniasrelated to Na+channel mutations:
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Ca channels
Skeletal muscle malignant Hyperthermia (MH) |
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Skeletal muscle
hypokaelemic periodic paralysis. |
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Lambert-Eaton Syndrome.
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Familial Hemiplegic Migraine (FHM) and Episodic Ataxia Type-2 (EP-2).
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K channels.
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Many distinct types: voltage-gated, activated by intracellular Ca, outward rectifiers, inward rectifiers, ligandactivated;
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Ligand(neurotransmitter)-activated channels.
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