Pacemaker of Heart

Q.

What is considered to be the natural pacemaker of heart?

Q. Sinoatrial node is present in

1. right auricle
2. right ventricle
3. left auricle
4. interventricular septum

Q. The correct route through which pulse-making impulse travels in the heart is:

1. SA node → AV node → bundle of His →Purkinje fibres → heart muscles
2. AV node → SA node → Purkinje fibres →bundle of His → heart muscles
3. SA node → Purkinje fibres → bundle of His → AV node → heart muscles
4. AV node → bundle of His → SA node →Purkinje fibres → heart muscles