Week 1 - The Cardiac Cycle Flashcards
What is systole and diastole?
systole is the ejection of blood from the heart. semilunar valves open. diastole is the filling phase.
How much of the cardiac cycle occurs during systole and diastole?
2/3rds is diastole. 1/3rd is systole
What are the 5 stages of the cardiac cycle?
Diastole, atrial systole, isovolumic ventricular contraction, ventricular ejection, isovolumic ventricular relaxation
What occurs during atrial systole?
SA node spreads depolarisation around the atrium and contracts, squeezing the last bit of blood out
what occurs during isovolumic ventricular contraction?
ventricles depolarise to close the mitral and tricuspid valves shut so blood doesnt go back into atria. isovolumic as ventricles are contrcating to build up pressure, but theres nowhere for blood to go.
What occurs in ventricular ejection?
pressure in ventricles exceed aorta and pulmonary trunk, so aortic and pulmonary valves open and blood is pushed through
What occurs in isovolumic ventricular relaxation?
after ejection, pressure falls in ventricles and semilunar valves shut. blood then fills into aorta slowly until pressure exceeds ventricles and pushes valves open again.
What occurs in late diastole phase?
tricuspid and mitral valves open and blood passively fills ventricles
What is the systolic and diastolic pressure?
systolic - maximum pressure in aorta. diastolic - minimum pressure in aorta
What is pulse pressure?
difference between systolic and diastolic pressures
When do we see systolic pressure and what’s its pattern?
when ventricle depolarises, graph shoots up from 80 to 120mmHg. as semilunar valves shut, pressure decreases slowly, but theres a notch where elastic recoils as aorta is elastic.
When does diastolic pressure end?
when pressure in aorta gets low, about 80mmHg, and this is lower than the pressure in the ventricles.
What is the pattern of volume and pressure in the left atrium?
3 waves - a, c and v.
- a wave is atrial contraction in atrial systole
- c wave is mitral valve closing and bulging into left atrium
- v wave is slow increase in pressure as blood is continuously flowing int atrium from L&R vena cavas. drops rapidly as mitral valve opens.
What is EDV and ESV? Values?
end diastolic volume and end systolic volume. 140ml and 60ml
What is the stroke volume?
difference between EDV and ESV - amount of blood that’s ‘stroked’ in ventricular contraction
Why is stroke volume not useful and what do we use instead?
it varies from person to person. bigger people have a bigger stroke volume. we use ejection fraction - percentage of blood in the ventricle thats pumped out. 60% is normal.
What is the isometric contraction phase?
semilunar valves shut and ventricle is contracting but volume is constant.
What is the rapid ejection phase?
semilunar valves open due to pressure and blood is shot out quick and short movement with high pressure. volume decreases quickly.
What is the slower ejection phase?
towards end of ventricular systole, blood pumped slighlty slower out (still FAST)
what is isometric relaxation phase?
ventricle isn’t contracting and all valves are shut. atrium is filling. ventricle stays at 60ml
What is the rapid filling phase?
diastole. atrium has higher pressure than ventricles and valves open - blood quickly fills ventricles
How many heart sounds do we have and which are hearable?
- only 1 and 2 are hearable and they are closure of mitral and tricuspid valves, and closure of semilunar valves
What are the 3rd and 4th heart sounds?
3rd is rapid passive filling phase.
4th is active filling phase - atria contracts.
What do we use to record the sounds made by the heart?
phonocardiogram
What may cause a heart murmur?
- may be normal.
- continuous murmur may be patent ductus arteriosus
- systolic murmur could be stenosis of aortic/pulmonary valves, or regurgitation through mitral/tricuspid valves
- diastolic murmurs could be stenosis of mitral/tricuspid valves, or regurgitation back through aortic/pulmonary valves
