cardiac cycle Flashcards
define systolic pressure
highest pressure in the aorta during contraction
~120
define diastolic pressure
lowest pressure in the aorta during relaxation
~80
define mean arterial pressure
MAP
1/3 of the way between diastolic and systolic pressure
~90-95
diastolic + 1/3 of systolic
define pulse pressure
difference between systolic and diastolic pressure
~40
define end diastolic volume
EDV
volume in the heart at the end of diastole
~140ml
define end systolic volume
ESV
volume in the heart at the end of systole
~60ml
define stroke volume
SV = EDV - ESV
~80ml
main determinant is the size of the person
define ejection fraction
EF = SV/EDV
~2/3
clinically more useful than SV
reduces with poor health
what does the A wave represent
atrial contraction
slight increase in pressure
what does the C wave represent
ventricular contraction
rise in pressure then quickly falls
pressure released when aortic valve opens and blood escapes out
what does the V wave represent
blood accumulates in atrium during ventricular systole
gradual increase in pressure
mitral valve opens and blood moves through to ventricles
pressure inside atria falls
define isometric contraction period
the ventricles are contracting but volume remains the same
rapid/slow ejection phase
during systole
rapid first then slower
rapid/slow filling phase
during diastole
rapid first then slower
if HR increases, filling phase decreases
>140bpm cuts into rapid filling phase which has a big impact
what occurs during late diastole
both sets of chambers are relaxed and the ventricles fill passively
what occurs during atrial systole
atrial contraction forces a small amount of additional blood into the ventricles
what occurs during isovolumic/isometric ventricular contraction
1st phase of ventricular contraction pushes AV valves closed but doesn’t create enough pressure to open SL valves
what occurs during ventricular ejection
ventricular pressure increases and exceeds the pressure in the arteries, SL valves open and blood is ejected
what occurs during isovolumic ventricular relaxation
ventricles relax, pressure in ventricles falls, blood flows back into cusps of SL valves and snaps them closed
what are the 2 ways the cardiac cycle can be represented
cardiac cycle graph
pressure-volume loop: LV vol vs LV pressure, runs anti-clockwise
what is the difference in circulation in the R and L side of the heart
shape would be the same for pulmonary circulation but with lower numerical values
lower pressure, same volume
pressure-volume loops
A. mitral valve opens (low vol and pressure)
B. mitral valve closes, EDV (isometric contraction phase)
C. aortic valve opens, diastolic pressure
D. aortic valve closes, systolic pressure, ESV
what causes the heart sounds
turbulence in the blood
normally 2 heart sounds are heard
what are the 2 normal heart sounds
S1 - mitral and tricuspid valves closing
S2 - aortic and pulmonary valves closing
abnormal heart sounds
murmurs
caused by abnormal turbulence of blood e.g. due to stenosis or regurgitation
systolic murmurs
between S1 and S2
aortic/pulmonary stenosis
mitral/tricuspid regurgitation
Lub shhh dup
diastolic murmurs
Between S2 and S1
mitral/tricuspid stenosis
aortic/pulmonary regurgitation
Lub dup shhh
what causes continuous background noise
murmur throughout the whole cycle
normally due to septal defect
pressure in L > R side of the heart
blood leaks from one side to the other throughout the whole cycle
can also occur due to calcification of the valves where they dont open or shut properly
