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