The heart Flashcards
What are the three stages of cardiac cycle?
- Ventricles relax, atria contract/ Atrial systole
- Ventricles contract, atria relax/ Ventricular systole
- Ventricles relax, atria relax/ Diastole
What happens during atrial systole?
-The ventricles are relaxed
-The atria contract,
-decreasing the volume of the chambers
-increasing the pressure inside the chambers
-Atrioventricular valves open
-This pushes blood into the ventricles
-There is a slight increase in the ventricular pressure and chamber volume as the ventricles receive the ejected blood from the contracted atria.
What happens during ventricular systole?
-The atria relax
-The ventricles contract
-decreasing their volume
-increasing their pressure
-The pressure becomes higher in the ventricles than the atria
-This forces the atrioventricular valves shut to prevent back-flow.
-The pressure in the ventricles is also higher in the aorta and pulmonary artery,
_which forces open the semi-lunar valves
-blood is forced out of the ventricles into these arteries (pulmonary and aorta).
What happens during diastole?
-The ventricles and the atria both relax
-Higher pressure in the pulmonary artery and aorta closes semi-lunar valves to prevent back-flow into the ventricles
-Blood returns to the heart and the atria fill again due to high pressure in the vena cava and pulmonary vein
-This starts to increase pressure of the atria.
-As the ventricles continue to relax, their pressure falls below the pressure of the atria
-So the AV valves open
-This allows blood to flow passively into the ventricles from the atria
-The atria contract, and the whole process begins again.
What does the right side of the heart do?
The right side pumps deoxygenated
blood to the lungs
What does the left side of the heart do?
The left side pumps oxygenated blood to the whole body.
Draw and label an image of the heart
Why does the left ventricle have thicker, and more muscular walls than right ventricle?
The left ventricle of the heart has thicker, more muscular walls than the right ventricles, because it needs to contract powerfully to pump blood all the way round the body.The right side only need to get blood to the lungs, which are nearby.
Why do ventricles have thicker walls than atria?
The ventricles have thicker walls than the atria, because they have to push blood out of the heart whereas the atria just need to push blood a short distance into the ventricles.
Function of the atrioventricular valve.
-AV valves link the atria to the ventricles
-stop blood flowing back into the atria when the ventricles contract.
Function of semi-lunar valves.
-SL valves link the ventricles to the pulmonary artery and aorta,
-stop blood flowing back into the heart after the ventricles contract
Function of the cords
The cords attach the AV valves to the ventricles to stop them being forced into the atria when the ventricles contract.
describe the mechanism of the valves
-The valves only open one way
-If there is a higher pressure behind a valve, it’s forced open
-If there’s a higher pressure in front of the valve it’s forced shut.
-This means blood only flows in one direction through the heart
