Cardiac cycle

Question 1

Describe the 2 phases of the cardiac cycle

Answer 1

Systole- contraction/emptying
Diastole- relaxation/filling

Question 2

What is the cardiac cycle time

Answer 2

0.8 seconds when heart rate is 75 beats per minute

Question 3

When the terms systole and diastole is used, the reference is to the ventricles until specified True or False

Answer 3

True

Question 4

What causes Atrial systole

Answer 4

Atrial depolarization

Question 5

What state are the ventricles in when atrial systole is occuring

Answer 5

Ventricles are in a relaxed state

Question 6

Why does the Atrioventricular valves open during Atrial systole

Answer 6

These valves are open because the pressure in the atria is greater then the pressure in the ventricles

Question 7

Since ventricles are always passively being filled what percentage of the blood is as a result of active filling from atria

Answer 7

Final 10-30% of blood volume

Question 8

Which heart sound is produces during atria contraction an why

Answer 8

S4 is produced because the ventricular wall vibrates if the ventricle is ‘stiff’ during atrial contraction

Question 9

What is the End diastole Volume

Answer 9

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

Question 10

What causes heart sound S1

Answer 10

Closure of the mitral and tricuspid valve

Question 11

Why does the mitral and tricuspid valves close

Answer 11

Myocytes contract causing increase in ventricular pressure which causes the closure of both valves

Question 12

Is there any change in volume when the myocytes contract leading to rapid rise in pressure in the ventricles

Answer 12

There is no change in ventricular volume as all valves are closed

Question 13

What occurs in ventricular systole

Answer 13

Rapid ejection of blood

Question 14

Why does the aortic and pulmonary valves open in ventricular systole

Answer 14

Pressures in the ventricles exceed aortic and pulmonary pressures

Question 15

When the intraventricular pressures fall below aortic and pulmonary pressures what happens

Answer 15

Aortic and pulmonary valves close resulting in the second heart sound S2

Question 16

What is End of systolic volume

Answer 16

Volume of blood remaining in a ventricle

Question 17

What is the End of systolic volume in the left ventricle (number)

Answer 17

50ml

Question 18

When mitral and tricuspid valves open resulting in a rapid inflow of blood what heart sound is heard

Answer 18

S3

Question 19

Why is the pressure on the right side of the heart lower than the left

Answer 19

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

Question 20

What are the pressures in the following, right atrium, right ventricle, left ventricle

Answer 20

Right Atrium- 0-8mm Hg
Right Ventricle- 25/6(2-8) mm Hg
Left ventricle 120/8(2-10)mm Hg

Question 21

What is the Dicrotic Notch

Answer 21

rebound of blood against the aortic valve causing a decrease then a rebound of aortic pressure

Question 22

What is stroke volume

Answer 22

Volume of blood pumped out by each ventricle per BEAT. About 70-80ml

Question 23

Formula for stroke volume

Answer 23

End Diastolic Volume - End Systolic Volume

Question 24

Ejection fraction

Answer 24

The percentage of ventricular end diastolic volume which is ejected with each stroke

Question 25

Formula for Ejection Fraction

Answer 25

EF= SV/EDV * 100