EVERYDAY SCIENCE

Detailed explanation-1: -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. The sinus node generates an electrical stimulus regularly, 60 to 100 times per minute under normal conditions.

Detailed explanation-2: -The SA node starts the sequence by causing the atrial muscles to contract. That’s why doctors sometimes call it the anatomical pacemaker. Next, the signal travels to the AV node, through the bundle of HIS, down the bundle branches, and through the Purkinje fibers, causing the ventricles to contract.

Detailed explanation-3: -It is located at the junction of the crista terminalis in the upper wall of the right atrium and the opening of the superior vena cava. These cells have the ability to spontaneous generate an electrical impulse. It is the integrated activity of these so-called pacemaker cells that form the SA node.

Detailed explanation-4: -The blood from the atria empties into the ventricles before the ventricles contract. After passing through the AV node, the electrical current then continues down the conduction pathway, through a pathway called the bundle of His, and into the ventricles.

Detailed explanation-5: -The impulse leaves the sinus node and travels a set path through the upper chambers, the atria, causing them to contract and squeeze blood into the lower chambers. The electrical signal then reaches the atrioventricular (AV) node. The AV node is in the middle of the heart, between the atrium and the ventricle.