The Cardiac Cycle Flashcards
Outline the name of the five steps of the cardiac cycle.
- Late diastole
- Atrial systole
- Isovolumic ventricular contraction
- Ventricular ejection
- Isovolumic ventricular relaxation
In which of the five steps is atrial systole?
2
In which of the five steps is ventricular systole?
3 + 4
Name and describe what is happening in Step 1.
Late diastole
Both sets of chambers are relaxed and ventricles fill passively.
Name and describe what is happening in Step 2.
Atrial systole
Atrial contraction forces a small amount of additional blood into ventricles.
Name and describe what is happening in Step 3.
Isovolumic ventricular contraction
First phase of ventricular contraction pushes AV valves closed but does not create enough pressure to open SL valves.
Name and describe what is happening in Step 4.
Ventricular ejection
As ventricular pressure rises and exceeds pressure in the arteries, SL valves are forced open and blood ejects.
Name and describe what is happening in Step 5.
Isovolumic ventricular relaxation
As ventricles relax, pressure in ventricles falls, blood flows back into the cusps of the SL valves and forces them shut.
Why do steps 3 and 5 have the term isovolumetric?
Because both the AV and SL valves are closed therefore no blood can enter or leave the ventricles, only the pressure can change which then forces the valves open.
iso = same isovolumetric = 'same volume'
Dystole can be referred to as the _______ phase of ventricular _________.
filling
relaxation
Systole can be referred to as the ________ phase of ventricular ___________.
ejection
contraction
Why does the pressure in the ventricles begin to fall during the ejection phase?
Ca begins being taken up by the SR or being pumped out the cell.
crossbridges will fall, pressure will fall eventually to below arterial pressure.
What is the diastolic pressure?
The minimum arterial pressure at the end if the diastole phase.
What is the systolic pressure?
The maximum arterial pressure during the ejection/contraction phase (systole).
What is the dicrotic notch?
The dicrotic notch is a small and brief increase in arterial blood pressure that appears when the aortic valve closes.
What is the normal arterial pressure (BP) value?
120/80
How do you calculate the pulse pressure?
systolic pressure - diastolic pressure
What is the normal value for the mean arterial pressure (MAP)?
90-95 mmHg
Roughly equal to diastolic pressure + 1/3 pulse pressure
What is the mean arterial pressure?
The force pushing the blood through the systemic circulation.
The atrium always has a ____ side pressure.
low
The aorta always has a _____ side pressure.
high
The ventricular pressure _______ during systole and is ______ during diastole.
rises
low
What is the significance of the A wave for the atrium?
Atrial contraction
This increases atrial pressure for a short period.
What is the significance of the C wave for the atrium?
Ventricular contraction, mitral valve pushes back slightly increasing pressure in the atrium.
What is the significance of the V wave for the atrium?
Blood returning to the atrium from the lungs increases pressure, as mitral valve is closed during systole.
What does EDV stand for?
What is this?
End diastolic volume
The peak volume of blood which has entered at the end of diastole.
What does ESV stand for?
What is this?
End systolic volume
minimum volume at end of systolic phase.
How do you calculate stroke volume (SV)?
SV = EDV - ESV
How do you calculate the ejection fraction?
How much blood will a healthy heart pump out at the end of diastole?
SV/EDV
about 2/3rds, an unhealthy heart would be less.
When during systole does the greatest volume of blood eject into the aorta?
The first 1/3, rapid ejection phase
When during diastole does the greatest volume of blood enter the ventricles?
The first 1/3, rapid filling phase
What is the active filling phase during diastole?
When the atria contracts, increasing its pressure, forcing additional volume of blood into the ventricles.
How would you describe the work of the atrium during diastole?
Its is mostly inactive in filling the ventricles, as this is a passive process.
It only really makes a difference when it contracts during the active filling phase.
Where on the pressure-volume loop would you read the end diastolic volume (EDV) from?
right vertical side (B-C)
Where on the pressure-volume loop would you read the end systolic volume (ESV) from?
left vertical side (A-D)
Where on the pressure-volume loop would you read the diastolic pressure from?
top right (C)
Where on the pressure-volume loop would you read the systolic pressure from?
peak of the curve, most superior
Where on the pressure-volume loop does the mitral valve open?
A
Where on the pressure-volume loop does the aortic valve open?
C
Where on the pressure-volume loop does the mitral valve close?
B
Where on the pressure-volume loop does the aortic valve close?
D
Where does the first sound on the phonocardiogram come from?
The tricuspid and mitral valves closing
Where does the second sound on the phonocardiogram come from?
The pulmonary and aortic valves closing
The time between the first two sounds represents _______.
systole
A systolic murmur would be heard with ________ of the A and P valves.
stenosis
A diastolic murmur would be heard with ________ of the A and P valves.
insufficiency
A systolic murmur would be heard with ________ of the T and M valves.
insufficiency
A diastolic murmur would be heard with ________ of the T and M valves.
stenosis
A septal defect would result in which type of sound?
one, continuous
What is used instead of stoke volume to assess the healthiness of someone’s heart?
The ejection fraction (stoke volume/ end diastolic volume).
Is stroke volume clinically relevant?
No, as it depends purely on the size of the person.
What can cause a systolic murmur?
stenosis of aortic/pulmonary valves or
regurgitation through mitral/tricuspid
What causes a diastolic murmur?
stenosis of mitral/ tricuspid valves
or
regurgitation through aortic/pulmonary valves
What causes a diastolic and systolic murmur?
septal defect
or calcification of valves causing stenosis and regurgitation
