Cardiac Cycle Flashcards
What is the cardiac cycle?
Is an ongoing sequence of contraction and relaxation of the atria and ventricles that keeps blood continuously circulating around the body.
What is cardiac contraction?
Systole
What is cardiac relaxation?
Diastole
What is the order of the cardiac cycle?
Atrial Systole-Ventricular Systole- Diastole
What is the 1st stage in the cardiac cycle?
Atrial Systole
What happens in Atrial Systole?
Atria contract, ventricles relax
In atrial systole what happens as the atria contract?
Volume decreases and pressure inside chambers increases
What does this change in pressure do?
Forces the AV valves to fully open and blood flows into ventricles. Pressure inside ventricles increases slightly
What is the 2nd stage in the cardiac cycle?
Ventricular systole
What happens in ventricular systole?
Ventricles contract, atria relax
In ventricular systole, what happens when the ventricles contract?
Volume decreases and pressure inside chambers increases further
What does this change in pressure inside the chambers do?
Forces the AV valves to close, preventing backflow
What also happens in ventricular systole?
Pressure in ventricles becomes higher than in the aorta and pulmonary artery forcing the SL valves to open.
What can now happen now the SL valves are open?
Blood can enter the arteries
What is the 3rd stage in the cardiac cycle?
Diastole
What happens in Diastole?
Atria and ventricles relax
How are the SL valves forced to close?
Due to high pressure in the aorta and pulmonary artery forces the SL valves to close.
What happens after the valves close?
Blood enters the atria as the pressure is lower in the atria than in the vena cava and pulmonary vein.
What then happens in diastole?
Pressure inside atria starts to increase forcing the AV valves to partially open so blood starts to flow passively into the ventricles
What is cardiac output (Q)?
Amount of blood pumped out of left ventricle in one minute
What is stroke volume?
Amount of blood pumped out of left ventricle in one cardiac cycle
What is the equation for cardiac output?
HR x SV
What do the following numbers represent? 120/80
120-Systolic Blood Pressure
80-Diastolic Blood Pressure
What is one reason why someone may have low blood pressure?
Volume of blood is low e.g. lots of blood has been lost
