Vandenberg_Lec7_2009 - Structure Function of Ion Channels...

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1 10/14/09 Structure & Function of Ion Channels Announcements: • Next Monday’s class will be a “Question & Answer” discussion session. Please email your questions ( [email protected] ). Also, Bring questions to class. • Midterm next Wednesday. You should bring a simple calculator (not graphing, not equation storage). • Sample exams from are posted on the class web site. Today: • Channelopathies—diseases caused by altered ion channels • Another way to study ion channels—patch clamp recording • Ion channel families & their structures • How do voltage-gated ion channels “sense” the voltage? What happens if there is an imbalance between Na conductance (favoring APs) and K or Cl conductances (favoring resting potential)? • Myotonia congenita (fainting goats): Absence of Cl channel causes less stable resting potential, multiple APs cause muscle tension • Hyperkalemic periodic paralysis (HyperPP) & paramyotonia congenita : A similar defect due to overactive Na channels • Long Q-T Syndrome: Overactive Na channels or block of HERG K channels can cause cardiac arrhythmia
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2 Failure of Na Channels to Inactivate Causes HyperPP Normal 2% Na Chan. not Inactivating: Myotonia 3% Na Channels not Inactivating: Myotonia, then paralysis Hyperkalemic Periodic Paralysis Diagnosis of HyperPP: Injection of solution containing potassium induces paralysis. Cardiac Long Q-T Syndrome Electrocardiogram (ECG) Is a record of the fluctuating potentials in the heart • QRS complex due to depolarization of ventricular myocytes • T wave due to repolarization of ventricular muscle • Q-T reflects length of ventricular action potential • Long Q-T interval can predispose individuals to arrhythmias and sudden cardiac death. Q-T interval
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Vandenberg_Lec7_2009 - Structure Function of Ion Channels...

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