Which is the normal pacemaker of the heart?

Which is the normal pacemaker of the heart?
 
  A) SA node
  B) AV node
  C) AV junction
  D) Ventricle

Question 2

Which of the following is NOT a part of the normal cardiac conduction system?
 
  A) Coronary sinus
  B) AV node
  C) Purkinje Fibers
  D) Internodal pathways

Question 3

What is the term for the fail-safe mechanism that allows a lower pacemaker to take over when a higher site fails?
 
  A) Polarization
  B) Irritability
  C) AV conduction
  D) Escape

Question 4

Which of the following does NOT happen when the sympathetic branch is stimulated?
 
  A) Heart rate increases.
  B) The heart becomes more irritable.
  C) Impulses go faster through the AV node.
  D) Ventricular conduction slows down.