Cardiac cycle Flashcards
thaxter
Describe the 2 phases of the cardiac cycle
Systole- contraction/emptying
Diastole- relaxation/filling
What is the cardiac cycle time
0.8 seconds when heart rate is 75 beats per minute
When the terms systole and diastole is used, the reference is to the ventricles until specified True or False
True
What causes Atrial systole
Atrial depolarization
What state are the ventricles in when atrial systole is occuring
Ventricles are in a relaxed state
Why does the Atrioventricular valves open during Atrial systole
These valves are open because the pressure in the atria is greater then the pressure in the ventricles
Since ventricles are always passively being filled what percentage of the blood is as a result of active filling from atria
Final 10-30% of blood volume
Which heart sound is produces during atria contraction an why
S4 is produced because the ventricular wall vibrates if the ventricle is ‘stiff’ during atrial contraction
What is the End diastole Volume
120ml- End diastole because while the ventricles are being filled it can no longer be relaxed so as it begins to fill its diastole comes to an end.
Remember diastole= relaxed/filling
What causes heart sound S1
Closure of the mitral and tricuspid valve
Why does the mitral and tricuspid valves close
Myocytes contract causing increase in ventricular pressure which causes the closure of both valves
Is there any change in volume when the myocytes contract leading to rapid rise in pressure in the ventricles
There is no change in ventricular volume as all valves are closed
What occurs in ventricular systole
Rapid ejection of blood
Why does the aortic and pulmonary valves open in ventricular systole
Pressures in the ventricles exceed aortic and pulmonary pressures
When the intraventricular pressures fall below aortic and pulmonary pressures what happens
Aortic and pulmonary valves close resulting in the second heart sound S2
What is End of systolic volume
Volume of blood remaining in a ventricle
What is the End of systolic volume in the left ventricle (number)
50ml
When mitral and tricuspid valves open resulting in a rapid inflow of blood what heart sound is heard
S3
Why is the pressure on the right side of the heart lower than the left
Because the blood on the right is coming from great distances in the body and blood moves from high pressure to low so to facilitate this right side should be low.
The pulmonary circulation needs to be a low pressure system to prevent fluid from entering into the interstitial space.
Remember too that the body doesn’t store blood anywhere so we don’t need a buildup
What are the pressures in the following, right atrium, right ventricle, left ventricle
Right Atrium- 0-8mm Hg
Right Ventricle- 25/6(2-8) mm Hg
Left ventricle 120/8(2-10)mm Hg
What is the Dicrotic Notch
rebound of blood against the aortic valve causing a decrease then a rebound of aortic pressure
What is stroke volume
Volume of blood pumped out by each ventricle per BEAT. About 70-80ml
Formula for stroke volume
End Diastolic Volume - End Systolic Volume
Ejection fraction
The percentage of ventricular end diastolic volume which is ejected with each stroke
