6. Cardiac Cycle Flashcards
What are the 5 main stages of the cardiac cycle?
- late diastole
- atrial systole
- isovolumic ventricular contraction
- ventricular ejection
- isovolumic ventricular relaxation
What happens in the late systole phase?
Both sets of chambers are relaxed and ventricles fill passively
What happens in the atrial systole phase?
Atrial contraction forces a small amount of additional blood into the ventricles (AV valves open)
What happens in the isovolumic ventricular contraction phase?
First phase of ventricular contraction pushes AV valves closed but does not create enough pressure to open semi-lunar valves
What happens in the ventricular ejection phase?
As ventricular pressure rises and exceeds pressure in the arteries, the semi-lunar valves open and blood is ejected
What happens in the isovolumic ventricular relaxation phase?
As ventricles relax, pressure in the ventricles falls, blood flows back into cusps of semi-lunar valves and snaps them closed
What is the mean arterial pressure?
93mmHg
What is the normal systolic pressure?
120mmHg
What is the normal diastolic pressure?
80mmHg
When does the a wave start in acv notation?
follows the atrial depolarisation (contraction) when increase in pressure in atria occurs
When does the c wave start in acv notation?
starts as soon as mitral valve closes and stops as soon as aortic valve opens (pressure released when aortic valve opens)
When does the v wave start in acv notation?
starts when blood comes back from the lungs to fill the atria (form pulmonary vein in left side of the heart)
What is the general end diastolic volume?
~140 ml
Why isn’t stroke volume generally not useful when looking at cardiac function?
Because it varies from person to person depending on size, sex, build etc
What is used instead of stroke volume to determine heart abnormalities?
ejection fraction
What should the ejection fraction be in a healthy individual?
2/3
What does the ejection fraction determine?
determines the pumping efficiency of the heart
What is the end-diastolic volume in the heart?
- volume of heart in ventricles (right or left) just before a systole
- volume of blood just after the filling phase
How is ejection fraction calculated?
Stroke volume/ end diastolic volume (SV/EDV)
How to calculate stroke volume?
end diastolic volume - end systolic volume (EDV-ESV)
What is the end-systolic volume in the heart?
- blood in the ventricle at the end of a contraction/style and the beginning of filling phase (diastole)
What is the difference in blood volumes between right and left sides of the heart?
right side has much smaller volumes (around 1/5th of the left side) since it’s easier to push blood into pulmonary circulation rather than systemic which requires more pressure changes (left side)
What creates the first “LUBB” sound?
mitral and tricuspid valves closing
What created the second “DUBB” sound?
aortic and pulmonary valves closing
Which valves should be open and which should be closed during diastole?
AV valves open
semi-lunar valves closed
Which valves should be open and which should be closed during systole?
AV valves closed
semi lunar valves open
What are heart murmurs generally caused by? (2)
- problems with valves
2. septal defects (holes in the heart)
What creates a murmur in the systolic phase? (systolic murmurs)
- stenosis of aortic/ pulmonary valves
2. regurgitation through mitral/tricuspid valves
What creates a murmur in the diastolic phase? (diastolic murmurs)
- stenosis of mitral/tricuspid
2. regurgitation through aortic/pulmonary
Which valves will have the stenosis in a systolic and diastolic phase?
the valves which should be open in the given phase (e.g. in systolic phase, semi lunar should be open so stenosis of aortic/pulmonary valves)
How much higher is the pressure in the left side of heart than right side?
should be 5x higher in the left side
If there is a septal defect, in which phases can stenosis and regurgitation occur?
in both phases; systolic and diastolic
Define systolic pressure.
Maximal arterial pressure during the contraction of the left ventricle (ventricular contraction)
Define diastolic pressure.
Minimum arterial pressure during relaxation and the dilatation of ventricles when ventricles fill with blood (during relaxation)
Define mean arterial pressure. (MAP)
Average arterial pressure during a single cardiac cycle (used to measure the BP in an individual)
Define pulse pressure.
- Difference between systolic blood pressure and diastolic blood pressure readings
- Represents the force that heart generates each time it contracts (systolic-diastolic) e.g. 120-80 = 40mmHg
Define stroke volume.
Volume of blood pumped from the left ventricle with each beat
Define ejection fraction.
measurement of the percentage of blood leaving your heart each time it contracts
Define isometric contraction period.
time between closure of AV valves and opening of semi-lunar valves
Define isometric relaxation period.
begins with closure of semi-lunar valve and start of opening of Av valves
What does phonocardiogram record?
Records sounds and murmurs made by the heart
What comes first, rapid or slower phases?
rapid phases always come first (rapid ejection before slow ejection and rapid filling before slow filling phases)
What is an acceptable range for normal BP?
120/80 - 140/90
What is pre-hypertension BP range?
120-139/ 80-89
What is stage 1 hypertension BP range?
140-159/ 90-99
What is stage 2 hypertension BP range?
160+/ 100+
