lecture 7 - CVS 3: the cardiac cycle Flashcards
what is the cardiac cycle?
cycle of pressure and volume changes in the heart chambers overtime the heart contracts and relaxes
what are the stages in the cardiac cycle?
1) ventricular filling
2) atrial contraction
3) isovolumic ventricular contraction
4) ventricular ejection
5) isovolumic ventricular relaxation
6) back to start
when does contraction occur?
systole
when does relaxation occur?
diastole
what is isovolumic ventricular contraction?
can generate force but theres no change in the volume of the chamber
closed system
where do the sounds of the heartbeat come from?
from the closing of the AV and semilunar valves
what is end diastolic volume (EDV)?
maximum volume in the ventricles prior to ventricular systole
what is end systolic volume (ESV)?
minimum volume in the ventricles prior to ventricle systole
how can you work out SV?
EDV - ESV
what is ejection fraction?
fraction of blood we eject from the heart
= SV / EDV
the heart sounds
2 main sounds can be heart - lubb dupp
first = AV valves closing second = SL valves closing
what happens if valves don’t close properly?
blood can leak and the heart has to work harder
reduced efficiency of the heart as a pump
diseases of valves
stenosis - cannot fully open
incompetence - insufficiency
what is systemic atrial blood pressure
measured at the level of the heart - upper arm
systolic/diastolic
maximum/minimum
120/80 mmHg
what happens when you put a stethoscope over an artery?
you shouldn’t be able to hear anything
in a normal artery you have laminar flow
how do you test systolic and diastolic pressure by auscultation?
1) inflatable cuff placed above large artery
2) stethoscope below large artery
3) increase pressure to close artery to stop blood flow - exceed normal systolic pressure
4) start to lower pressure in cuff
5) when artery starts to open you get the first korotokoff sound from turbulent flow
6) increase in turbulent flow
7) when cuff pressure if less than diastolic pressure you get laminar flow again - no sound
how can you determine systolic and diastolic pressure from auscultation?
first sound = peak systolic pressure
when sound disappears = diastolic pressure
what is dichroic notch?
represents when the aortic valves close
• you get some back flow of blood causing a rebound in pressure
• pressure goes up slightly and back down
what is mean arterial pressure (MAP)?
pressure in the arteries averaged over time
MAP = DP + 1/3(SP-DP)
what is pulse pressure?
difference between SP and DP
SP - DP
