Cardiac cycle

Question 1

3 Stages of cardiac cycle

Answer 1

Diastole
Atrial systole
Ventricular systole

Question 2

What happens during diastole in terms of contraction?

Answer 2

Both the atria and ventricles are relaxed as blood from pulmonary vein/ vena cava fills the atria

Question 3

What happens during diastole in terms of the valves?

Answer 3

Because the pressure in atria is bigger than in ventricles due to the filling of blood into atria which increases pressure slightly
then this causes the atrioventricular valves to open and blood to fill ventricle

Question 4

What happens during diastole in terms of ventricular volume?

Answer 4

Slowly increases as blood from atria empties into ventricles

Question 5

What happens during atrial systole in terms of contractions?

Answer 5

The atria contract decreasing volume in atria, increasing pressure
The ventricles will remain relaxed, so pressure in atria>pressure in ventricle

Question 6

What happens in atrial systole in terms of valves?

Answer 6

The atrial ventricular valves will open because pressure in atria is larger than in ventricles

Question 7

What happens in atrial systole in terms of volume of blood?

Answer 7

Increased in ventricular volume of blood due to emptying from the atria into the ventricles

Question 8

Why is there delay in semi lunar valve opening before atria ventricular valve closes?

Answer 8

So blood isn’t flowing in2 directions

Question 9

What happens in ventricular systole in terms of contractions?

Answer 9

Both the ventricles and atria are relaxed
So volume of ventricle increases and pressure inside decreases

Question 10

What happens in ventricular systole regarding the valves?

Answer 10

The pressure in ventricles dropped due to stopping contracting
And the pressure in arteries is higher due to the ventricle contracting
Once the pressure in armies > pressure in ventricles, the semi lunar valves shut

Question 11

What happens during ventricular systole in terms of ventricular volume?

Answer 11

Eventually reaches plateau as all blood had emptied into arteries but now the semi lunar valve shut

Question 12

How does the cycle repeat?

Answer 12

Blood returns to the heart, via vena cava (deoxygenated) or from pulmonary vein (oxygenated)
Blood enters atria, causing pressure in atria to increase above ventricular pressure
Thus atrioventricular valves open and blood enters ventricle before atria contracts = enters diastole

Question 13

How does atrium contract?

Answer 13

Sinoatrial node depolarises, so wave of electrical excitation passes through atrial walls causing atria to contract