BION 3202

1. BION 3202 Lecture 5. Whole-heart Electrophysiology

2. Where does the first impulse come from and why?

6. Electrical Heterogeneity The concept of electrical heterogeneity is well established. Some heterogeneity in electrical function is important for normal synchronous cardiac function.The concept of electrical heterogeneity is well established. Some heterogeneity in electrical function is important for normal synchronous cardiac function.

7. You�re in the laboratory looking at a heart beating in ringer�s solution. Normally, the ringer�s solution has 12 mM Nai, 145 Nao, 155 Ki and 4 Ko. You raise the extracellular K to 30 mM. What happens to the ventricular rhythm and why? Using the goldman equation, you raise the resting membrane potential to -42 mV, which inactivates the sodium channels because it�s above -60mV the point for Na to activate. This means no INa is available for depolarization and the ventricles can�t initiate an action potential and therefore beat.Using the goldman equation, you raise the resting membrane potential to -42 mV, which inactivates the sodium channels because it�s above -60mV the point for Na to activate. This means no INa is available for depolarization and the ventricles can�t initiate an action potential and therefore beat.

8. Answer: BAnswer: B

9. Answer: BAnswer: B

10. Answer: DAnswer: D

11. Answer: AAnswer: A

12. Answer: B.Answer: B.

13. -98mV which means that increasing potassium permeability should bring resting membrane potential closer to potassium�s reversal potential.-98mV which means that increasing potassium permeability should bring resting membrane potential closer to potassium�s reversal potential.

14. In which graph is the K+ permeability during the pacemaker potential increased? A B Answer: BAnswer: B

15. AA

16. Student Presentations

17. Next Class: The ECG Chapter 14, pages 480-484 ECG, EKG Dipole