The Cardiac Cycle Flashcards
Name the three main stages of the cardiac cycle in order
Atrial systole, ventricular systole, diastole
Describe atrial systole
The walls of the atria contract, atrial volume decreases and atrial pressure increases. The pressure in the atria rises above the pressure in the ventricles, forcing the AV valves open. Blood is forced into the ventricles. There is a slight increase in ventricular pressure and chamber volume as the ventricles receive the blood from the atria.
Describe ventricular systole
The walls of the ventricles contract, ventricular volume decreases and pressure increases. Pressure in the ventricles rises above that in the atria. This forces AV valves to close , preventing back flow of blood. Pressure in ventricles rises above that in aorta and pulmonary artery forcing SL valves to open so blood is forced into the arteries and out of the heart.
Describe diastole
Ventricles and atria are both relaxed. Pressure in ventricles drops below that in aorta and pulmonary artery, forcing SL valves to close. Blood begins to fill in atria as the pressure is less than that of the vena cava and pulmonary vein. Some blood passes passively into the ventricles.
What is the key function of valves in the heart?
They ensure blood flows in the right direction
Where are the atrioventricular valves located?
Between the atrium and ventricle
Describe the opening of AV vales
When the ventricular walls relax, the pressure in the ventricles drops below the pressure in the atria. The blood in the atria pushes the AV valves open.
Describe the closing of the AV valves
After the av valve opens, blood enters the atria and ventricles, causing pressure to slowly rise. When the ventricle is full, a swirling action around the valve causes it to close.
Where are the semilunar valves located?
Between the atria and the arteries
Name the two arteries of the heart
Aorta and pulmonary artery
Name the two veins of the heart
Vena cava and pulmonary vein
Describe the closing of the semilunar valves
Before ventricular systole, the pressure in the arteries is higher than the pressure in the ventricles, causing the SL valves to be closed.
Describe the opening of the semilunar valves
When ventricular systole takes place, the pressure in the ventricle exceeds the pressure in the arteries, causing the semilunar valves to be pushed open.
