The Cardiac Cycle Flashcards
What are the stages of the cardiac cycle?
1) Late diastole (both sets of chambers are relaxed and ventricles fill passively)
2) Atrial systole (atrial contraction forces amll amount of additional blood into ventricles)
3) Isovolumic ventricular contraction (first phase of ventricular contraction pushes AV valves closed but does no create enough pressure to open semilunar valves)
4) Ventricular ejection (ventricular pressure exceeds that in the arteries, opening semilunar valves and blood is ejected)
5) Isovolumic ventricular relaxation (ventricles relax and pressure falls, blood flows back into cusps of semilunar valves and snaps them closed)
What happens during late diastole?
Both sets of chambers are relaxed and ventricles fill passively
What happens during atrial systole?
Atrial contraction forces a small amount of additional blood into ventricles
What happens during isovolumic ventricular contraction?
First phase of ventricular contraction pushes AV valves closed but does not create enough pressure to open semilunar valves
What happens during ventricular ejection?
Pressure inside ventricles exceeds pressure in the arteries, the semilunar valves open and blood is ejected
What happens during isovolumic ventricular relaxation?
As ventricles relax, pressure in ventricles falls, blood flows back into cusps of semilunar valves and snaps them closed
What do the muscles of the heart do as they depolarise?
Contract
What causes the valves to open and close?
Raising and decreasing the pressure inside chambers
How can you describe the pressure inside the atrium?
Low pressure
How can you describe the pressure inside the aorta?
High pressure
How can you describe the pressure inside the ventricles?
Balance between high and low pressures
What happens as soon as the pressure inside the ventricle is greater than the pressure inside the atrium?
Closes the AV valves
What causes the pressure inside the ventricles to continue rising once the AV valves have closed?
Muscles continue to contract until the pressure is greater than the aorta
What happens once the pressure inside the ventricles is greater than the pressure inside the aorta?
SL valves open
Why does blood pressure continue to rise once the SL valves open?
More cross bridges continue to be formed, causing muscle contraction
Why do heart muscles in the ventricles stop contracting?
Calcium is pumped back into the sarcoplasmic reticulum or back into the cell so there are fewer cross bridges
What happens once the pressure inside the ventricles drops below that of the aorta?
SL valves close
When do the AV valves open?
When the pressure inside the ventricles drops below that inside the atrium
Why does pressure inside the aorta closely follow pressure inside the ventricles?
There is nothing between the two when the SL valves are open
What is systolic pressure?
Maximum pressure in the aorta
What is maximum pressure in the aorta called?
Systolic pressure
What is diastolic pressure?
Minimum pressure inside the aorta
What is minimum pressure inside the aorta called?
Diastolic pressure
What is pulse pressure?
Difference between systolic and diastolic pressure
What is the difference between systolic and diastolic pressure called?
Pulse pressure
What is mean arterial pressure roughly?
Diastolic pressure plus 1/3 the difference between diastolic and systolic pressure
What are the 3 blips in the atrium pressure called?
A wave
C wave
V wave
What is the A wave of the atrium pressure?
Atrial contraction increases pressure on blood and pushes it into the ventricle
What is the C wave of atrium pressure?
Ventricle contraction pushes the mitral valve shut which pushes on the blood in the atrium and causes the increase in pressure
What is the V wave of atrium pressure?
While the ventricle is contracting, blood is flowing from the lungs into the atrium to meet the closed mitral valve, causing the pressure to gradually increase
What does EDV stand for?
End diastolic volume
What is end diastolic volume (EDV)?
Volume of blood in the ventricle at the end of filling it (diastole)
What is the volume of blood in the ventricle at the end of filling it (diastole) called?
End diastolic volume (EDV)
What does ESV stand for?
End systolic volume
What is end systolic volume (ESV)?
Volume of blood in the ventricle at the end of pumping blood out of it (systole)
What is the volume of blood in the ventricle at the end of pumping blood out of it (systole) called?
End systolic volume (ESV)
What is stroke volume?
Difference between EDV and ESV
What is the difference between EDV and ESV called?
Stoke volume
How much blood is usually left in the heart after systole?
60ml
Why is not all of the blood pumped out of the heart during systole?
Allows the strength of the contraction to be varied
What does stroke volume tell you?
How large a person is, larger people have a greater stroke volume
What formula described ejection fraction?
Ejection fraction = SV/EDV
What does ejection fraction tell you?
How healthy you are, a healthy person should be 2/3 with the number going down as health declines
How does ejection fraction change as health declines?
Decreases
What is the rapid ejection phase?
First 1/3 of the ejection phase (systole)
What is the first 1/3 of the ejection phase (systole) called?
Rapid ejection phase
What is the slower ejection phase?
Second 2/3 of ejection phase (systole)
What is the second 2/3 of the ejection phase (systole) called?
Slower ejection phase
What is the rapid filling phase?
First 1/3 of the filling phase (diastole)
What is the first 1/3 of the filling phase (diastole) called?
Rapid filling phase
What is the slower filling phase?
Second 2/3 of the filling phase (diastole)
What is the second 2/3 of the filling phase (diastole) called?
Slower filling phase
Why is it important that most of the blood returns to the heart during the first 1/3 of diastole?
As if the heart rate is increased most of the cycle is cut at the end of the diastole with only a little of systole being lost
How does the right side of the heart compare to the left?
Same heart rate
Same volume
Smaller pressures
Why are the pressures of the right side of the heart smaller than the left?
A lot easier to push blood through pulmonary circulation than systemic
How does the pressure of the right side of the heart compare to the left?
Pressure of the right side is 1/5 the size
What is the diagram called that illustrates the pressures inside the heart?
Pressure-volume loop
What is A?
End of systole/start of diastole
Mitral valve opens and blood flows into ventricle
Ventricle is very large so no change in pressure
What is B?
Ventricle starts contracting so pressure increases
Causes mitral valve to close and pressure to continue to rise
What is C?
Pressure inside ventricle is higher than aorta so aortic valve opens
Pressure continues to rise as ventricle continues to contract
Volume starts to drop as blood is pumped into aorta
What is D?
Ventricle pressure is lower than aorta so aortic valve closes
Pressure continues to drop as muscles relax
Where is the ESV on a pressure-volume loop?
Top left (D)
Where is EDV on a pressure-volume loop?
Bottom right (B)
What is the stroke volume on a pressure-volume loop?
Difference between the right and the left
What does the area inside a pressure-volume loop tell us?
What volume of blood is pressurised by how much
What is a phenocardiogram?
A chart of the sounds made by the heart
What is a chart of the sounds made by the heart called?
Phenocardiogram
What is A?
Mitral and tricuspid valves closing
What is B?
Aortic and pulmonary valves closing
What is C?
Stenosis of aortic/pulmonary or regurgitation through mital/tricuspid
What is A?
Stenosis of mitral/tricuspid or regurgitation through aortic/pulmonary
What is the sound between the noises of the two valves closing?
Diastole
What can sometimes be heard between the sounds of the two valves closing?
Murmurs
What is A?
Septal defect
