Cardiac cycle Flashcards
What are the 3 main stages of the cardiac cycle?
-atrial systole
-ventricular systole
-diastole
What does systole mean?
contraction
What does diastole mean?
relaxation
What makes valves open/close?
pressure change
purpose of passive filling
to allow blood to flow from veins to atria to ventricle
purpose of atrial systole
to squeeze remaining blood into ventricle
purpose of ventricular systole
force blood out of ventricle and into aorta/pulmonary vein
purpose of diastole
1) What happens in passive filling?
-blood flows passively into the atria from the veins
-70% of blood also flows down into the ventricles due to gravity as the AV valves are open
2) How is the other 30% of blood pushed into the ventricles?
*through atrial systole
-atria muscles contract and atrial pressure increases over ventricular pressure
-blood is pushed into ventricles through AV valves
-volume of atria decreases
3) What makes the AV valves snap shut?
*ventricular systole
-atria muscles relax
-ventricle muscle contracts, starting from apex so the pressure in ventricles is now higher than in the atria
-AV valves close to prevent backflow of blood
3)How does blood leave the heart?
*ventricular systole
-pressure in ventricles is now higher than in arteries
-SL valves forced open
-blood forced into the pulmonary vein/aorta, so volume in ventricle decreases
4) What makes the SL valves shut again?
*diastole
-pressure in arteries increases and is now higher than pressure in ventricles
-this forces SL valves to close
4) What makes the AV valves open for atrial systole to occur again?
*diastole
-atrial and ventricle muscles are relaxed
-blood from vena cava/pulmonary vein enters atria (passive filling begins)
-pressure in atria is higher than ventricles so AV valves open
Describe the timings that the atria spends in systole/diastole
systole: 0.1 secs
diastole: 0.7 secs
Describe the timings that the ventricle spends in systole/diastole
diastole: 0.1 sec
systole:0.3 secs
diastole: 0.4 secs
When do the AV valves open?
-when the pressure in the atria is high
-in late diastole (passive filling) and during atrial systole
When do the AV valves close?
-when the pressure in the ventricles is high
-during ventricular systole and early diastole
When do SL valves open?
-when pressure in ventricles is high
-during late ventricular systole
When do SL valves close?
-when pressure in arteries is high
-during diastole, atrial systole and early ventricular systole
What levels are the pressures in the different areas, during atrial systole?
atria: high
ventricle: low
vein: high
What levels are the pressures in the different areas, during ventricular systole?
atria: low
ventricle: high
vein: high
What levels are the pressures in the different areas during diastole?
atria: low
ventricle: low
vein: high
Why is there always a high pressure in the vein?
high pressure maintained to pump blood constantly
