Cardiovascular physiology III

1. During sympathetic stimulation the depolarization phase of an impulse is faster. Name the intracellular second messenger that facilitates the opening of the L-channels.

cAMP

2. What is the effect of digitalis on SA node?

Depresses / inhibits the generation of impulse

3. What is the normal duration of AV nodal delay?

0.1 s

4. Why are atria and ventricles not simultaneously excited although they have a rapid conducting system?

Due to the AV-nodal delay

5. What is the conduction rate of the SA node?

0.05 m/s

6. What is the conduction rate of the AV node?

0.05 m/s

7. What is the advantage of the normal AV-nodal delay?

Helps in emptying of the atrial blood or complete filling of the ventricles

8. What is the conduction rate of the Bundle of His?

1 m/s

9. What is the conduction rate of the Purkinje fibres?

4 m/s

10. Which part of the conducting system in the heart has the highest velocity / speed of conduction?

Purkinje fibres

11. What is the algebraic sum of action potentials of the myocardium recorded extra-cellularly called?

Electrocardiogram

12. On what principle the ECG is recorded from the body surface using leads, though it is the record of potentials of the heart?

Body acts as a volume conductor

13. What type of recording is it called when the ECG is recorded using two active electrodes?

Bipolar recording

14. Name the triangle that is gormed using three standard limb leads in an ECG recording.

Einthoven’s triangle

15. Why is the atrrial repolarization wave generally not visible in a normal ECG?

It is submerged by the QRS complex

(Physiology; UMS 2008)