Question

Beginning with all chambers of the heart in the "relaxed" phase, describe the cardiac cycle in mammals, with systole and diastole of the atria and ventricles. For each time point in the cycle you select, state the following:

Whether the atria and ventricles are contracting or relaxing

Whether the AV valves and semilunar valves are closed or open

Whether the pressure in the atria and ventricles is high or low

Answer 1

cardiac cycle is the sequence of event of blood flow of the body or the circulation of one beat (0.8 SECONDS)  and electric signalling occurs which causes relaxation and contraction of the heart.

cardiac cycle is performed in a sequential manner and the organs and vessel which do take in cardiac cycle is a lungs and heart and some vessels that are pulmonary vessel aortic vessel and vena cava's that contribute to this.

1 Always the right atrium receives the deoxygenated blood from the bpdy through superior and inferior vena cava and and at this time the atrium filling occurs due to diastole and both av valve and semilunar valve gets closed and atrium which is right gets filled with dexygenated blood and this phase is the first phase known as isovolumetric relaxation during which both types of valves are closed and ventricles are relaxed and which low pressure and atrial pressure use to increasing when filling starts with vena cava's.

2 Now ventricular filling starts and AV valve gets opened and still ventricles stays in the diastole condition and atrium gets emtpied giving the blood to ventricles this occurs in three steps

rapid ventricular filling in which relaxed empty ventricles fills slowly and volumes increases rapidly

now fillings gets more slow as ventricles are somewhat filled called diastasis and

3 third is the phase of atrial systole (P WAVE) of ECG or contraction of the atrium forcing remaining blood into ventricles .

4 Now there is a phase of ventricular contraction or ventricular systole begins as the action potential from AV node enters ventricles as this phase shows the QRS complex of the ecg

now at this stage both av closed and semilunar valves are closed and first heart sound LUB is produced due to closure of both the valves and artrium gets relaxed and venrticles starts contracting pressure starts bulding and this is systole for ventricles and this shutting of AV valves called ISOVOLUMETRIC CONTRACTION.

Nows as pressures increeases more in ventricles forces semilunar valve to open and blood starts doing out and ends a contraction and relaxation starts in ventricles and semilunar valves closes again and that shows bit increase in blood pressure,

and this phase shows the second heart sound.

and along with this process of the right side of heart same on the whole the blood comes in right ventricles goes in the lungs via pulmonary trunk and here it got oxygenated and oxygenated blood via pulmonary veins in the left atrium where it then goes into left ventricle and then via aorta supplies to whole body.

5 when the semilunar valves are closed and then tricuspid and bicuspid valves are opened when pressure falls in ventricles and blood flows from atrium to ventricles and this time no contraction occurs due to low presure gravitational flow.

Atrium and ventricles use to contracts due to systole and relaxes due to diastole and pressure gets increases when valves are closed and contraction incereases.