Cardiac Cycle Flashcards
What is the cardiac cycle?
the sum of all the cardiac events from the beginning of one heart beat to the beginning of the other heart beat are called a cardiac cycle
What is the location of SA node ?
In the right atrium near the opening of the superior vena cava
Why are atria called primer pumps for the ventricles?
There is a delay of 100 Ms between the Atrial and ventricular contractions this allows atria to pump blood into the ventricles before the powerful ventricular contractions. Therefore the atria are called primer pumps
What is the total duration of the cardiac cycle?
The total duration of the cardiac cycle including the systole and diastole is the reciprocal of the heart rate per min.
What is the effect of HR increase on the cardiac cycle and it’s major events diastole systole?
As the HR increases the duration of each cardiac cycle decreases. Reduces diastolic and systolic volumes, the duration of AP and the period of contraction.
Heart normally pumps ______ percentage of blood than the body requires?
300 to 400% of the blood than the body requires.
Why is atrial dysfunction is unlikely to be noticed unless a person exercise?
80% of the pre-systolic volume of blood flows directly into the ventricles without atrial contraction. The atrial contraction only adds 20% to the pre-systolic volume. Therefore, the symptoms of atrial failure occasionally only develops during exercise.
The ‘a’ wave in atrial pressure waves represents ?
Atrial contraction causing an increase of right atrial pressure of 4 to 6 mmHg and left atrial pressure of 7 to 8 mmHg.
The ‘c’ wave in atrial pressure waves represents?
It is caused partly by the slight backflow of blood into the atria when the ventricles begin to contract and by bulging of the AV valves towards the atria due to increased pressure build up in the ventricles
The ‘v ‘ waves in atrial pressure curves represent?
It is caused by the slow flow of blood from the vena cave into the atria while the AV valves are closed. It disappears when the AV valves open
What is known as the period of rapid filling of the ventricles ?
The period of rapid ventricular filling lasts about first third of the diastole. During this the blood accumulated in the atria during ventricular systole rapidly Force open the AV valves as the ventricular pressure falls to it’s end diastolic volume.
What happens during the middle third of the diastole?
The blood continues to diffuse into the ventricles from the great veins through the AV valves directly without atrial contraction.
What happens during the last third of the diastole?
The atrial contraction pumps 20% blood into the ventricles.
Describe the period of isovolumic contraction?
The ventricles require an additional 0.2 to 0.3 seconds to build up sufficient pressure to push the semilunar valves to open against the pressure in the aorta and pulmonary arteries. Therefore, during this period contraction occurs in the heart but there is no emptying this period is called the period of isovolumic contraction.
Describe Period of ejection?
It is the period of ventricular emptying. It occurs when the left ventricular pressure increases slightly above 80mmHg and right ventricular pressure above 8mmHg.
