The cardiac cycle Flashcards
What is the first stage in the cardiac cycle
Late diastole - both sets of chambers are relaxed and ventricles fill passively
What is the second stage in the cardiac cycle
atrial systole - atrial contraction forces a small amount of blood into the ventricles
What is the third stage in the cardiac cycle
Isovolumic ventricular contraction - first phase of ventricular contraction is enough to close the AV valves but not enough to open the semi lunar valves
What is the fourth stage in the cardiac cycle
Ventricular ejection - as the ventricles pressure exceeds the atrial pressure, its causes the semi lunar valves to open and blood be expelled from the ventricles
What is the fifth stage in the cardiac cycle
Isovolumic ventricular relaxation - Ventricles relax, causing a decreases in pressure, blood flows back on to the semi lunar valves and snaps them closed
What is responsible for the a wave in measuring atrial pressure in the heart
A wave follows the p wave on an ECG
Therefore shows arterial depolarisation causing an increase in arterial pressure
What valves open and shut to create the c wave in arterial pressure in the heart
c wave starts as soon as mitrovalve closes and stops as soon as aortic valve opens
What is responsible for the V wave in the measure of arterial pressure in the lungs
due to venous return coming back to the lungs in systolic stage through pulmonary vein
What causes the arterial pressure to decrease and match the ventricle pressure in the lungs
Mitral valve opens
What causes the massive increase in ventricle pressure in the heart
Mitral valve close causing the pressure in the ventricles to increase as are filled with blood
What triggers the aortic valves to open
When ventricular pressure exceeds aortic pressure
What causes the aortic valve to close
When ventricular pressure decreases as muscles relax from pushing out stoke volume, blood flows back on to the aortic valves and snaps them closed
What causes the dicrotic notch in the aortic pressure
ventricles push out the blood, it absorbs energry, releases blood then the aortic valve shuts causing a rebound in pressure
What causes further decrease in aortic pressure, and equalises ventricular and arterial pressure
Mitral valve opening
What is the usually end diastolic pressure (EDV)
140ml
What is the usually end systolic volume
60ml
What is it important for there to be end systolic volume
So heart doesn’t pump all the blood thats in it - reserve for exercise
How is the stroke volume determined
The difference between EDV and ESV
How do you calculate the ejection fraction
SV/EDV
What is the clinical importance of the ejection fraction
As stroke volume will vary according to the person, where ejection fractions shows how much of the blood present in the heart is pumped out
What should the ejection fraction typically be
2/3rds
Why does doubling the heart rate have little effect on diastolic volume
As increasing heart rat has little effect on filling stage but rather how fast blood can be expelled from the heart
What is the difference between right and left side of the heart in terms of pressure and volume and why
Volume of the right and left side is the same, however the pressure of the right side is much less due to less force needed to push blood around pulmonary circulation rather than systemic circulation
What is the effect of mitral valves opening on the pressure and the volume of the left ventricles
The left ventricles volume increases while pressure remains the same
What happens to cause mitral valves to close
Ventricular pressure increases
What is called when the ventricular pressure is increases with a high volume of blood in the lungs that cant escape
isometric contraction stage
What valve opens to allow blood out to the body, and what effect does this have on ventricular pressure and volume
Aortic valve open
This means ventricular pressure continues to increase as stroke volume is pushed out and ventricles volume decreases
After the volume of stroke volume is fully expelled from the lungs what happens to the ventricular pressure and volume
The ventricular pressure decreases again, while the End systolic volume remains constant
What does the decrease in ventricular pressure have on the effect of the aortic valve
Causes the aortic valve to shut
What is the typical lub dub sound caused by a phonocardiogram
How is this sound created
Mitral & tricuspid valves closing
followed by
Aortic & pulmonary valves closing
The turbulence of the blood caused by the valves shutting
What does a phonocardiogram investigate
Heart murmurs - abnormal heart rhythms
What features of the valves can cause heart murmurs
Stenosis of valves
Regurgitation of valves
What continues to pick up a continual rhythm on the phonocardiogram
septum defect
When is the rapid filling stage
start of diastole when the mitral valve open
What causes the rapid ejection stage
systolic pressure exceeding aortic pressure - aortic valves open
What causes the isometric contraction stage
When the pressure increases but the blood remains in the ventricles
