Cardiac cycle

Question 1

Atrio - ventricular valves

Answer 1

> after systole the ventricular walls relax
pressure in ventricles drops
blood in atria pushes AV valves open
blood goes from the atria into the ventricles
valves close when atria relaxes
as ventricles contract the pressure of the blood rises
blood moves into atria
blood cant flow back due to valves

Question 2

Semilunar valves

Answer 2

> before ventricular contraction the pressure is higher than in ventricles
> semi lunar valves are closed 
> pressure increases due to systole
> semi lunar valve is pushed open
> ventricle relaxes
> pressure drops
> blood flows back into ventricles
> semi lunar valve pushed closed
> prevents blood returning

Question 3

Pressure in blood vessels

Answer 3

> walls in the arteries stretch as the blood leaves the heart
as blood moves out of the aorta pressure drops