The Cardiac Cycle Flashcards
What are the stages of the cardiac cycle?
Late diastole
Atrial systole
Isovolumic Ventricular Contraction
Ventricular ejection
Isovolumic Ventricular relaxation
Explain late diastole
Both sets of chambers are relaxed and ventricles fill passively
Explain atrial systole
Atrial contraction forces a small amount of additional blood into ventricles - contracts due to depolarisation
Explain isovolumic ventricular contraction
First phase of ventricular contraction which pushes AV valves closed but not enough pressure to open semilunar valves
What is End diastolic volume?
EDV - max. amount of blood in ventricles
Explain ventricular ejection
As ventricular pressure rises and exceeds pressure in arteries, the semilunar valves open and blood is ejected
Explain isovolumic ventricular relaxation
As ventricles relax, pressure in ventricles falls. Blood flows back into cusps of semilunar valves and snaps them closed. Blood now cant get in or out of ventricles
What is End Systolic Volume?
ESV - min. blood in ventricles
What causes a plateau in volume during cardiac cycle?
Is the volume of blood when both valves are closed so entry and exit of blood cant happen
Happens during both isometric contraction phase and relaxation phase
Explain what the dicrotic notch it
Is due to the elastic properties of the aorta
Aortic valve closes and there is elastic recoil of aorta - causing blip
What is pulse pressure?
Difference between systolic and diastolic pressure
Usually around 40mmHg
What is the MAP?
Mean arterial pressure
1/3 of systolic and diastolic pressure
Around 90mmHg
Why does pressure in aorta decrease slowly?
Elastic walls help to maintain pressure
Describe atrium pressure on graph?
Can see a wave, c wave and v wave
What does the a wave represent on left atrium pressure graph?
Caused by atrial contraction which is a squeeze on aorta which increases pressure to squeeze last bit of blood inti ventricle
What does the c wave represent on left atrium pressure graph?
When mitral valve closes, it can bulge into left atrium and increase left atrium pressure
Pressure is released when aortic valve opens
What does the v wave represent on left atrium pressure graph?
Even during diastole there is blood returning from lungs to left atrium - atrium has low pressure so when blood flows in pressure gradually increases
Blood flows atrium to ventricle so pressure decreases
What is stroke volume?
Difference between end diastolic volume and end systolic volume
Usually around 80ml but depends on size of person
What is the ejection fraction?
What % of blood in ventricle is pumped out with each contraction
SV/EDV
What are the different phases of volumes during cardiac cycle?
Isometric contraction
Rapid ejection
Slower rejection
Isometric relaxation
Rapid filling
Slower filling
How does phonocardiogram pick up heart sounds?
Turbulence in blood flow
What are additional heart sounds called?
Murmurs
What is the 1st heart sound due to?
Closure of the AV valves
What is the 2nd heart sound due to?
Closure of semilunar valves
What is the 3rd heart sound due to?
Rapid passive filling phase - AV valves open, blood into ventricles
What is the 4th heart sound due to?
Active filling phase - atria contract and squeeze last bit of blood
What are the 2 things that can cause a pathological murmurs?
1 - Valve that should be opened is narrowed or stenosed causing turbulent blood flow
2 - Valve which should be closed is leaky and allows blood to regulate through it
Explain a systolic murmur?
Hear lub shush dub
Stenosis of semilunar valves or regurgitation through AV valves
Explain a diastolic murmur?
Hear lub dub shush
Stenosis of AV valves or regurgitation through semilunar valves
What can a continuous murmur be due to?
Patent ductus arteriosus
What is Patent ductus arteriosus?
Ductus arteriosus is small vessels that join aorta to pulmonary trunk during development - meant to close after birth but if not then continuous murmur
Pressure in aorta higher than pulmonary trunk so some blood continuously flows and creates turbulent flow
