The pace setter in the heart is called as
A. AV node
B. SA node
C. Purkinje fibres
D. Papillary muscles

Hint:- Pace setter is the part which controls the pace of the action potential generated from the pacemaker of the heart. The initiation is done by the pacemaker but the conduction from the interatrial septum is mediated by the role of AV nodes which act as pace setters of the generated potential.

Complete step-by-step solution:-Heart is the organ involved in the circulation of blood to the whole human body. The heart beat production is due to cardiac muscles which are auto rhythmic in nature. Auto rhythmic fibres generate the action potential continuously that triggers the contraction of the heart.
The conduction of this action potential through the heart follows a sequential order:
The generation of action potential occurs in the SA node of heart a known sinoatrial node also known as pacemaker of heart). In SA nodes maximum numbers of action potential can be generated of order 70-75 per minute.
The generated potential passes through the atria and is passed on to AV nodes of the heart known as atrioventricular nodes also known as pace setters of heart.
On passing through the as atrioventricular node the potential reaches the atrioventricular bundles also known as Bundle of His. It is a point where divergence of potential can occur from atria to ventricles of the heart.
From Bundle of His the potential reaches to its terminal fibres known as Purkinje fibres. The extension of these terminal fibres is throughout the ventricles of the heart. It conducts the potential rapidly to the remaining myocardium of ventricles of the heart.
Thus the correct option is A.

Note:- For the complete heart cycle to occur the conduction of action potential from the sinoatrial node to the Purkinje fibre should occur. If in any case SA nodes do not work properly, the generation of potential will be done by AV nodes of the heart.