Cardiac Cycle Flashcards
What happens when pressure is greater in front of the valve
The valve closes
What happens when pressure is greater behind the valve
The valve opens
What causes the valves to open and close
The valves are forced open and closed by pressure of the blood in the heart
What prevents the atrioventricular valves from inverting
Heart tendons (chordae tendinae)
What holds the atrioventricular valves in place
Papillary muscles
What is the cardiac cycle
This is the complete cycle of events in the heart from the beginning of one heart beat to the beginning of the next
What is the contraction of the heart called
Systole
What are the two divisions of the systole
The atriole systole (the atria contract) and the ventricular systole (the ventricles contract)
What follows the contraction in the cardiac cycle
A period of relaxation known as diastole
What are the three stages that the cardiac cycle can be split into
Diastole- the heart relaxes and blood enters the atria
Atria systole- the atria contract and push blood into the ventricles
Ventricular systole- the atria relax, the ventricles contract and blood moves out of the arteries
Describe what occurs during diastole
The atria and ventricular walls are in diastole (relaxed). Blood moves into the heart via the pulmonary vein and vena cava. The atrioventricular valves are open (due to the pressure of the blood against them) and the semilunar valves are closed as the pressure is higher in the arteries than in the ventricles.
Describes what happens during atrial systole
The atria walls contract, because they are in systole while the ventricular walls are still in diastole; they are relaxed. The atrioventricular valves are still open and the semilunar valves are closed. Therefore, blood moves to the ventricles.
What happens when ventricular systole occurs
The atria are relaxed and the atrioventricular valves close due to the pressure of blood against the valve flaps.
During ventricular systole why does the semilunar valves open
They open due to pressure being higher in the ventricles than in the arteries
How does blood move during ventricular systole
Blood moves out of the ventricles to the arteries and then to the lungs or body. Then the cycle starts again
Explain why the wall of the left ventricle is thicker than the wall of the left atrium
This gives it more muscle to create more force as it needs to create higher higher pressure to push blood with greater force. This way the left ventricle is able to pump blood further to all parts of the body
Explain how pressure changes in the heart bring about the closure of the atrioventricular (bicuspid valve)
Ventricular systole contracts, this contraction raises ventricular pressure. This pressure becomes higher than atrial pressure. This higher pressure closes the atrioventricular valves.
