the cardiac cycle Flashcards
what is systole
contraction of the heart
what is diastole
filling of the heart, following systole
Describe the cardiac cycle
late diastole - blood flows passively into ventricles, both chambers relaxed
atrial contraction (systole)- atria contract and squeeze additional bit of blood into ventricles
Isovolumnic ventricular contraction- ventricles contract which push the AV valves closed
ventricular ejection- pressure inside ventricles rises and exceeds that in the arteries so semi-lunar valves open and blood gets ejected
isovolumnic ventricular relaxation- ventricles relax following systole, pressure in ventricles falls, semi-lunar valves snap closed
what is mean arterial pressure (MAP) and how do you calculate it
MAP is the pressure driving blood through the systemic circulation. calculated: diastolic blood pressure + 1/3 of pulse pressure (SBP-DBP)
what is the peak volume called at end of diastole
End Diastolic Volume
what is volume called at end of systole and how much is it approximately
eND systolic Volume - approx 60ml
how do you calculate SV
SV= EDV-ESV
how do you calculate ejection fraction & what should it be in a healthy heart
Ejection Fraction= SV/EDV - should be around 2/3 in a healthy heart
during what phase is most blood ejected and what follows it
rapid ejection phase which is the first third of the filling phase. The next 2/3 are the slower ejection phase
during what phase does most blood fill the ventricles and what follows it
rapid filling phase which takes up the first third of the filling phase. The next 2/3 are the slower filling phase
what follows the rapid and slower filling phase ?
active filling phase- in which the atria contract ad force additional blood into the ventricles, however most blood has entered during the rapid & slow filling phase
what effect does HR increasing have on EDV?
HR increasing up to double has little effect on EDV because most blood goes into ventricles during first third = rapid filling phase. However, if it increases more than 150bpm, it will cut into the rapid filling phase and hence EDV will decrease
what is one similarity and one difference relating to the right and left sides of the heart
SV is the same on both sides as the same amount of blood is pumped out, however pressure on the right is about a fifth lower than the left because more pressure is required to pump blood to the systemic circulation than the pulmonary circulation
what indicates the first heart sound lub?
onset of systole - mitral & tricuspid closing
what indicates the second heart sound dub?
end of systole/onset of diastole- pulmonary & aortic closing
