1. Physiology of the Heart Daniel Hodyc Department of Physiology UK 2.LF

2. 1. Action potential in myocardium 2. Prapagation of AP, arrythmias 3. Excitation - contraction coupling Physiology of the Heart

3. Action potential in myocardium significantly differs from AP in skeletal muscle or nerve Skeletal muscle,nerve Myocardium

4. The origin of different shape of AP curve is in voltage gated L-type calcium channels

5. Ca ions influx strongly influences the strenght and duration of myocardial contraction Katecholamines - beta-receptor on the cardiomyocyte membrane - adenylalcyclace, cAMP - activation of L-type Ca channels Acetylcholine - muscarine receptors - adenylatcyclase inhibition Plasmatic concentration of Ca

6. Ca channels action potential duration force of contraction treatement of congestive heart failure ??? Effect of Ca-channel blockers (Verapamil, nifedipin)

7. Longer AP prevents the tetanic contraction in myocardium

8. The length of plato phase in influenced by K+ channels and differs in various parts of myocardium

9. Greater activity of K+ channels in atrium causes shorter plato phase Atrial myocardiumVentricular myocardium

10. Hypercalemia causes higher excitability and leads to arrythmias

11. AP differs in normal myocardium and conductive sytem Ventricular myocardiumConductive system - SAN

12. AP in SAN is caused by different channels Na - „funny channels“ Ca - channels K+ channels

13. Effect of acetylcholine on heart frequncy Slower depolarization Hyperpolarization

14. Spreading of the AP in the heart Reentry mechanism

15. Excitation-contration coupling - initiation fo the contraction Special components of cardiomyocytes - T-tubuls, gap junctions a SR Ce infulx from the extracellular space is necessary fo initiation of the contraction, by the contraction requires much more ions

16. Excitation-contraction coupling - Ca release from SR Calcium induced Ca release from SR Contraction force is dependent on the concentration of Ca in SR

17. Excitation-contraction coupling - relaxation Energy demanding process Secondary active transport Effect of cardiac glykosides

18. Relationship between force and frequency Bowdich (Treppe) effect Higher frequency Intracellular Na Shorter diastole Less Ca expelled form the cell

19. Effect of catecholamines Ca channel phosphorylation Faster contraction Phospholamban Faster relaxation

20. Thank you for your attention Pictures and schemes – Berne, Levy - Physiology; 6th - Arronson, Ward - The CV System at a Glance - Guyton, Hall - Textbook of Medical Physiology, 11th