Question

The cardiac cycle in the heart refers to the repetitive pumping process that begins with the onset of cardiac muscle contraction and ends with the beginning of the next contraction. Predict the changes that occur in the following parts of the heart after the second heart sound and before the first heart sound of the next cycle: 1. aorta 2. left ventricle 3. left atrium

Answer 1

Second Heart sound is produce due to the closer of semilunar (aortic and pulmonary) valve. This sound indicates the end of ventricular systole and beginning of ventricular diastole.

First heart sound is produced due to the closer of mitral valve and tricuspid valve(AV valve) of the heart. This indicates the beginning of ventricular systole and the end of atrial systole.

Changes occur in the heart after second heart sound and before the first heart sound are as follows:

• Changes after second heart sound: After the second heart sound AV valve opens and blood rushes fast into the ventricle that is rapid filling phase of ventricle. This rush of blood in the ventricle produce third heart sound. After that ventricle fills with the blood and this is the ventricular diastole phase. Last phase of ventricular diastole overlaps with the atrial systole. During this ventricular filling phase aortic valve remain closed and don't pump any blood from the left ventricle.
• Changes before first heart sound: before the first heart sound atria of the heart contract and ventricular filling is completed. After the ventricular filling ventricular systole will start after the closer of AV valve and in ventricular systole phase semilunar valve will open and pump the blood through aorta and pulmonary artery. So before the first heart sound left ventricle fill fully with blood and left atrium will undergoes fully contraction phase for pumping of blood to the ventricle.

1. Aorta will remain close during the ventricular filling phase due to closer of aortic valve. aorta will open in the ventricular systole phase after opening of Aortic valve and pump the blood from left ventricle to the whole body

2. Left ventricle fills with the blood during ventricular filling phase after the second heart sound, the filling phase will finish and overlap with the atrial systole before the first sound will produce.

3. After the second heart sound produce left atrium is in the diastole phase. and before the first heart sound the left atrium will undergoes in contraction phase(atrial systole).