Depolarisation and repolarisation actually initiate ___________ in different chambers of heart?

(1) contraction and relaxation

(2) relaxation and contraction

(3) thickening and thinning

(4) thinning and thickening

The action potential causes ______ and then the ______ to undergo ______ followed by ______.

(1) ventricles, atria, contraction, relaxation

(2) atria, ventricles, contraction, relaxation

(3) ventricles, atria, relaxation, contraction

(4) atria, ventricles, relaxation, contraction

A specialised nodal tissue embedded in the lower corner of the right atrium, close to atrio-ventricular septum, delays the spreading of impulses to heart apex for about 0.1 sec.

This delay allows -

1. blood to enter aorta.
2. the ventricles to empty completely.
3. blood to enter pulmonary arteries.
4. the atria to empty completely.

Atrial systole

1.  Increases the flow of blood into the ventricles by 70 percent

2.  Is due to the generation of the action potential in AVN

3.  Increases the flow of blood into the ventricles by 30 percent

4.  Coincides with ventricular systole

Which of the following is known as the natural pacemaker of the heart?

1.  Sino atrial node

2.  Atrioventricular node

3.  Bundle of His

4.  Purkinje fibers