MEDICAL PHYSIOLOGY
                   Electrophysiology Conference Quiz 2A
                             September 18, 2001

1. How does hyperthyroidism enhance susceptibility to insulin-induced
flaccid paralysis?

                    By increasing the number of sodium-potassium pumps in
cell membranes.

2. By what mechanism does hypokalemia produce flaccid paralysis?

                    Increased sodium channel inactivation due to
depolarization of the resting potential of skeletal muscle.

3. Why does hypokalemia widen the QRS complex?

          Slows conduction velocity of ventricular action potential due to
          reduction of rate of phase 0 depolarization.

4. What effect does hypokalemia have on the maximum diastolic potential of
SA-node cells?

          Causes maximum diastolic potential to be less negative.

5. How and by what mechanism does exercise affect the susceptibility to
hypokalemia-induced flaccid paralysis?

          Reduces susceptibility by shifting potassium out of the cell;
          increased potassium efflux associated with increased action
          potential firing.

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                            MEDICAL PHYSIOLOGY
                   Electrophysiology Conference Quiz 2B
                             September 20, 2001

1. How is the transmembrane flux of potassium affected by insulin?

          Increased potassium influx due to enhanced
          sodium-potassium pump activity

2. What role does membrane resting potential play in hypokalemia-induced
flaccid paralysis?

          Resting potential depolarization decreases excitability
          by increasing sodium channel inactivation; reduced
          number of resting sodium channels

3. Why does hypokalemia increase the QT interval?


          Decreased potassium conductance reduces delayed
          rectifier potassium current thereby increasing the
          duration of the ventricular action potential.

4. What effect does hypokalemia have on the rate of phase 4 depolarization
of SA-node cells?

          Speeds phase 4 depolarization

5. How and by what mechanism does inhibition of beta2-adrenergic receptors
affect the susceptibility of the hyperthyroid patient to attacks of flaccid
paralysis?

          Reduces susceptibility by reducing sodium-potassium pump
          activity.