Cardiac Cycle

Question 1

How long does the cardiac cycle last?

Answer 1

0.8 seconds

Question 2

What are the two main phases of a heartbeat?

Answer 2

Diastole

Systole

Question 3

What are the features of diastole?

Answer 3

Lasts approximately 2/3 of each beat

Ventricular relaxation
The ventricles fill with blood

Split into 4 distinct phases

Question 4

What are the features of systole?

Answer 4

Lasts approximately 1/3 of each beat

Ventricular contraction
Ventricles generate pressure then eject blood into the arteries

Split into 3 distinct phases

Question 5

What are the phases of the systole?

Answer 5

Isovolumetric contraction
Rapid ejection
Slow ejection

Question 6

What is end-diastolic volume?

Answer 6

When the heart is filled

108ml

Question 7

What is end-systolic volume?

Answer 7

Volume of blood after contraction

36ml

Question 8

What is the stroke volume?

Answer 8

Difference between end-diastolic and end-systolic volume

72ml

Question 9

What is ejection fraction?

Answer 9

Percentage of blood that is pumped into circulation
Describes the action and contractility of the heart

around 67%

Question 10

What are the stages of diastole?

Answer 10

Atrial systole
(Systole)
Isovolumetric relaxation
Rapid passive filling
Slow passive filling

Question 11

What does the cardiac cycle being with?

Answer 11

Atrial systole

Question 12

What is atrial systole on an ECG?

Answer 12

P-wave

Question 13

What occurs during atrial systole?

Answer 13

Atria already almost full from passive filling driven by pressure gradient. Atria contract to ‘top-up’ the volume of blood in ventricle

Question 14

What heart sound is atrial systole responsible for?

Answer 14

4th heart sound
Abnormal
Would normally be silent

Question 15

What does an abnormal 4th heart sounds indicate?

Answer 15

congestive heart failure pulmonary embolism

tricuspid incompetence

Question 16

What is the second phase of the cardiac cycle?

Answer 16

Isovolumetric contaction

Question 17

What is isovolumetric contraction on an ECG?

Answer 17

QRS complex marks the start of ventricular depolarisation

Question 18

What occurs during isovolumetric contraction?

Answer 18

This is the interval between AV valves (tricuspid & mitral) closing and semi-lunar valves (pulmonary & aortic) opening

Contraction of ventricles with no change in volume

Question 19

What heart sound is isovolumetric contraction responsible for?

Answer 19

1st heart sound (‘lub’) due to closure of AV valves and associated vibrations

Question 20

What is the third phase of the cardiac cycle?

Answer 20

Rapid ejection

Question 21

What marks the start of rapid ejection?

Answer 21

Opening of the aortic & pulmonary valves

Question 22

What occurs during rapid ejection?

Answer 22

As ventricles contract pressure within them exceeds pressure in aorta and pulmonary arteries. Semilunar valves open, blood pumped out and the volumes of ventricles decrease.

Question 23

What is the heart sound for rapid ejection?

Answer 23

No heart sounds are heard for this phase

Question 24

What is the fourth phase of the cardiac cycle?

Answer 24

Reduced ejection

Question 25

What does reduced ejection mark?

Answer 25

End of systole

Question 26

What occurs during reduced ejection?

Answer 26

Reduced pressure gradient means aortic & pulmonary valves begin to close Blood flow from ventricles decreases and ventricular volume decreases more slowly As pressures in ventricles fall below that in arteries, blood begins to flow back causing semilunar valves to close

Question 27

What is the fifth stage of the cardiac cycle?

Answer 27

Isovolumetric relaxation

Question 28

What occurs during isovolumetric relaxation?

Answer 28

The aortic & pulmonary valves shut, but the AV valves remain closed until ventricular pressure drops below atrial pressure. Atrial pressure continues to rise. Dichrotic notch (green line) caused by rebound pressure against aortic valve as distended aortic wall relaxes.

Question 29

What heart sound is isovolumetric relaxation responsible for?

Answer 29

2nd heart sound (‘dub’) due to closure of semilunar and associated vibrations

Question 30

What is the sixth phase of the cardiac cycle?

Answer 30

Reduced passive filling

Question 31

What can reduced passive filling also be known as?

Answer 31

Diastasis

Question 32

What occurs during reduced passive filling?

Answer 32

Ventricular volume fills more slowly | The ventricles are able to fill considerably without the contraction of the atria.

Question 33

What are the difference between the left and right sides of the heart?

Answer 33

the pressures in the right heart and pulmonary circulation are much lower (peak of systole – 25mmHg in pulmonary artery) Left: 120mmHg

Question 34

What are the similarities between the left and right side of the heart?

Answer 34

The patterns of pressure changes in the right heart are essentially identical to those of the left right ventricle ejects same volume of blood as left

Question 35

What determines the preload that stretches the resting ventricular muscle?

Answer 35

Blood filling the ventricles during diastole

Question 36

What represents afterload?

Answer 36

The blood pressure in the great vessels | aorta and pulmonary artery

Question 37

What does increased preload result in?

Answer 37

Increased stroke volume | Frank-Starling relationship

Question 38

What does increased afterload result in?

Answer 38

Decreased stroke volume | Decreased shortening

Question 39

What is cardiac output equal to?

Answer 39

Heart rate x Stroke volume

Question 40

What affects stroke volume?

Answer 40

Preload Afterload Contractility

Question 41

Define contractility?

Answer 41

Contractile capability (or strength of contraction) of the heart

Question 42

How can contractility be measured?

Answer 42

Ejection fraction

Question 43

What increases contractility?

Answer 43

Sympathetic stimulation More calcium release Increases gradient of pressure and volume relationship Increased force

Question 44

What does hardening and narrowing of the aortic valve result in?

Answer 44

Reduces flow | Increases afterload

Question 45

What does acute blood loss result in?

Answer 45

Reduces venous return | Decreases preload

Question 46

What does exercise result in?

Answer 46

Venous return increases due to venoconstriction and skeletal muscle pump, and contractility is increased via sympathetic nervous system