when the ventricular walls contract then what happen?

Answer 1

When the ventricular walls contract this raises the pressure inside the ventricles (because the volume shrinks dramatically) and this pressure exceeds the opening pressure of the valve (aortic valve or pulmonary valve - ie. exceeding the diastolic pressure in the corresponding artery) and blood flows out of the ventricle into the artery (aorta or pulmonary artery). This is systole


Then there is ventricular relaxation and repolarization of the muscle fibres as the ventricle fills from venous return. (ie Diastole)

Then at the end of diastole the atria fire (p-wave of the ECG) which gives the ventricles one last bit of loading of blood and then the ventricles contract (with the QRS of the ECG).

Answer 2

You get a pulse. If the ventricles in the brain contract then you have a real problem - jk. Is there something specific you want to know?