The cardiac cycle L7 Flashcards
what is the cardiac cycle
cycle of pressure and volume changes in the heart chambers (both atria and ventricles) every time the heart contracts and relaxes
what are the 4 phases of the cardiac cycle
- ventricular filling
- isovolumetric ventricular contraction
- ventricular ejection
- isovolumetric ventricular relaxation
- diastole: relaxation systole: contraction
what happens at late diastole
AV open SL closed
both chambers are relaxed fill passively
what happens at atrial systole
atria contract forcing small about of blood into ventricle
what happens at isovolumetric contraction
ventricular contraction forces AV closed creating lubb sound
now both values are shut so EDV is reached
what is EDV
End Diastolic volume
- maximum blood volume in ventricles
what happens at ventricular ejection
ventricular pressure rises exceeding that of it in the arteries
forcing SL open creating dubb sound
blood is ejected
what happens at isovolumetric ventricular relaxation
ventricles relax so pressure falls AV valves closed
blood flows back into SL valves closing them
ESV reached
what is ESV
end systolic volume- minimum blood volume in ventricles
on pressure area of Wiggers Diagram, what happens at A,B,C and D
use pp for diagram
A: AV valves close as first part of isovolumetric ventricular contraction
both valves close causing increase in pressure on ventricle
B: SL valves open: pressure inside ventricle is higher than that of artery
C: SL close: ventricular pressure no longer higher than artery
- dicrotic notch: increase in pressure of the aorta due to blood coming back down and hitting SL shut
D: AV valves open
on ventricular volume area of Wiggers Diagram, what happens at E and F
use pp for diagram
E: end diastolic volume
F: end systolic volume
how to work out stroke volume from wiggers diagram
EDV-ESV
how to work out ejection fraction from wiggers diagram
refers to blood left in ventricle
stoke volume/ EDV
how to work out heart rate
if a cycle occurs every 1 second
there will be 60 beats per min
how to work out stoke volume
cardiac output X heart rate
what causes heart sounds and how can it be measured
Two main sounds can be heard (lubb dupp)
First (S1) – Atrioventricular (AV) valves closing
Second (S2) – Semilunar (SL) valves closing
Phonocardiogram (see ECG practical)
give 2 examples of disease of valves
- stenosis
- Valves do not open as they should so harder for heart to achieve stoke volume- may exhaust heart
- congestive heart failure - incompetence
- do not close correctly- leak
what is mean arteriole pressure
Pressure in artery averaged over time
- Can be ‘estimated’ by this relationship: MAP = DP + 1/3 Pulse Pressure (PP)
what is the functional importance of elastic recoil ability of arteries
Stoke volume going into artery causing it to expand
- Expand and back to normal helps to keep moving blood away from the heart
how is systematic arterial blood pressure measured
measured at level of heart
- Systolic/diastolic
Maximum/minimum
120/80 mmHg (normal values)
