Question

In the human heart, how and why the diastole of 4 chambers occur? *Elaborate diastole of heart*

Could you explain in details cardiac cycle and specifically in the pressure difference between chambers?

Answer 1

Cardiac cycle:-

To begin with all the four chamber of heart are in a relaxed stage. They are in joint diastole. As the tricuspid and bicuspid valve are open blood from pulmonary veins and venacava flows into the left and right ventricle respectively through the left and right atria. The semilumas valve are closed at this stage . The SAN node now generate action potential which stimulates both the atria to undergo simultaneous contractions called the atria systole. This increases the flow of blood into the ventricle up to 30%.

- The action potential is conducted to the ventricular side by the AVN and AV bundle and from there it is transmitted to the whole ventricle by bundle of hiss. This causes the ventricular muscles to contract , the atria undergo diastole , coinciding with ventricular systole.

- Ventricular systole increases the ventricular pressure causing closure of tricuspid and bicuspid valve due to attempted back flow of blood into the atria.

- As the ventricular pressure increases further , the semilunar valve guarding the pulmonary artery and the Aorya open, allowing the blood in the ventricle to flow through these vessels into the circulatory pathway.

- The ventricle now relax and the ventricular pressure falls causing the closure of semilunar valve which prevent the back flow of blood into the ventricle.

- As the ventricular pressure decline further , the tricuspid and bicuspid valves are pushed open by the pressure in the atria caused by blood which was being emptied into them by the veins.

- the blood now once again moves freely to the ventricle . The venyrvent and atria are in a joint diastole stage. Soon SAN generate action potential and the events described above continue.

Hope this helps thanks