ANATOMY

Detailed explanation-1: -The SA (sinoatrial ) node generates an electrical signal that causes the upper heart chambers (atria) to contract. The signal then passes through the AV (atrioventricular) node to the lower heart chambers (ventricles), causing them to contract, or pump. The SA node is considered the pacemaker of the heart.

Detailed explanation-2: -Cardiovascular Function: Central Nervous System Control Heart rate is established by spontaneously depolarizing pacemaker cells in the sinoatrial node, and the rate of depolarization of these pacemaker cells is modulated by parasympathetic and sympathetic neural activity.

Detailed explanation-3: -An electrical stimulus is generated by the sinus node (also called the sinoatrial node, or SA node). This is a small mass of specialized tissue located in the right upper chamber (atria) of the heart.

Detailed explanation-4: -Both nodes are capable of producing their own impulses. Though under normal conditions, when both are functional, SAN leads and AVN follows. That is, SAN activity determines the rate of heart beat. Hence it can be referred to as pace setter for the heart.

Detailed explanation-5: -The SA node is normally the dominant, driving pacemaker because it has the highest intrinsic rate of spontaneous automaticity.